- ID:
- ivo://CDS.VizieR/J/AJ/160/62
- Title:
- 2018-2019 Xinglong BVR photometry of V0599 Aur
- Short Name:
- J/AJ/160/62
- Date:
- 08 Dec 2021
- Publisher:
- CDS
- Description:
- Combining all available photometric data from various surveys and literature with our observations, we present 10 sets of light curves for the eclipsing binary V0599 Aur covering a timescale of 20 yr. During the last two decades, the O'Connell effect continuously varied and went through at least two flips between positive and negative effects. The photometric solutions from our two sets of multicolored light curves show that V0599 Aur is a W-type shallow contact binary with an active spot on the secondary. Its absolute parameters are determined by combining the Gaia distance with the photometric solutions. The period investigation reveals a secular decrease and a cyclic variation in its orbital period. The former mainly originates from the mass transfer from the more massive secondary to the less massive primary. The latter can be preferentially explained as a result of cyclic magnetic activity of the secondary, with three observational supports: (1) the existence and evolution of an active spot suggested by the long-term photometry, (2) periodic variation in both the O'Connell effect and relative luminosity, and (3) weak correlations between O'Connell effect/relative luminosity changes and cyclic period variation. Together with the cyclic period variation and its theoretical reasonability by Applegate's mechanism, we suggest that the secondary of V0599 Aur is a solar-type magnetic-activity star with an approximately 11 yr active cycle. Furthermore, by combining the secular period decrease with the Roche-lobe model, we infer that V0599 Aur is evolving from the marginal contact state controlled by thermal relaxation oscillation theory to the overcontact state.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/459/199
- Title:
- XMM-Newton survey of two Upper Scorpius regions
- Short Name:
- J/A+A/459/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied X-ray emission from young stars by analyzing the deep XMM-Newton observations of two regions of the Upper Scorpius association with an age of 5Myr. Based on near infrared and optical photometry we identified 22 Upper Scorpius photometric members among the 224 detected X-ray sources. We derived coronal properties of Upper Scorpius stars by performing X-ray spectral and timing analyses. The study of four strong and isolated stellar flares allowed us to derive the length of the flaring loops.
- ID:
- ivo://CDS.VizieR/J/AJ/145/143
- Title:
- XMM observations of {alpha} Per
- Short Name:
- J/AJ/145/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the analysis of an archival observation of part of the {alpha} Persei cluster obtained with XMM-Newton. We detected 102 X-ray sources in the band 0.3-8.0 keV, of which 39 of them are associated with the cluster as evidenced by appropriate magnitudes and colors from Two Micron All Sky Survey photometry. We extend the X-ray luminosity distribution (XLD) for M dwarfs, to add to the XLD found for hotter dwarfs from spatially extensive surveys of the whole cluster by ROSAT. Some of the hotter stars are identified as a background, possible slightly older group of stars at a distance of approximately 500 pc.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A150
- Title:
- XMM observations of {lambda} Ori cluster
- Short Name:
- J/A+A/530/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied the X-ray properties of the young (~1-8Myr) open cluster around the hot (O8 III) star {lambda} Ori and compared them with those of the similarly-aged sigma Ori cluster to investigate possible effects of the different ambient environment. We analysed an XMM-Newton observation of the cluster using EPIC imaging and low-resolution spectral data. We studied the variability of detected sources, and performed a spectral analysis of the brightest sources in the field using multi-temperature models.
- ID:
- ivo://CDS.VizieR/J/MNRAS/367/781
- Title:
- XMM observations of NGC 2547
- Short Name:
- J/MNRAS/367/781
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The following tables describe the results of a survey for X-ray (0.3-3 keV) sources in the young (30Myr) NGC 2547 open cluster using the XMM-Newton EPIC instrument. Table 1 lists the details of X-ray sources which are correlated with optical cluster members. Table 2 catalogues the cross-identifications with optical catalogues for the sources in Table 1 and derives their X-ray luminosities and X-ray to bolometric flux ratios. Table 3 lists the X-ray properties of sources which are uncorrelated with cluster members. Table 7 lists the correlations between cluster members detected by XMM-Newton and those detected 7 years earlier by the ROSAT HRI instrument, along with the X-ray luminosities and flux ratios as determined by the HRI.
- ID:
- ivo://CDS.VizieR/J/A+A/456/977
- Title:
- XMM observations of NGC 2516 stars
- Short Name:
- J/A+A/456/977
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the characteristics of the X-ray variability of stars in the cluster NGC 2516 as derived from XMM-Newton/EPIC/pn data. The X-ray variations on short (hours), medium (months), and long (years) time scales have been explored. We detected 303 distinct X-ray sources by analysing six EPIC/pn observations; 194 of them are members of the cluster. Stars of all spectral types, from the early-types to the late-M dwarfs, were detected.
- ID:
- ivo://CDS.VizieR/J/A+A/446/501
- Title:
- XMM observations of sigma Ori cluster
- Short Name:
- J/A+A/446/501
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an XMM-Newton observation of the young (~2-4Myr) cluster around the hot star sigma Orionis. In a previous paper (Sanz-Forcada et al., 2004A&A...421..715S) we presented the analysis of the RGS spectrum of the central hot star; here we discuss the results of the analysis of the full EPIC field. We have detected 175 X-ray sources, 88 of which have been identified with cluster members, including very low-mass stars down to the substellar limit. We detected eleven new possible candidate members from the 2MASS (Cat. <II/246>) catalogue.
- ID:
- ivo://CDS.VizieR/J/ApJ/820/L28
- Title:
- XMM obs. of two regions west to {kappa} Ori
- Short Name:
- J/ApJ/820/L28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- X-rays are a powerful probe of activity in early stages of star formation. They allow us to identify young stars even after they have lost the IR signatures of circumstellar disks and provide constraints on their distance. Here, we report on XMM-Newton observations that detect 121 young stellar objects (YSOs) in two fields between L1641S and {kappa} Ori. These observations extend the Survey of Orion A with XMM and Spitzer (SOXS). The YSOs are contained in a ring of gas and dust apparent at millimeter wavelengths, and in far-IR and near-IR surveys. The X-ray luminosity function of the YSOs detected in the two fields indicates a distance of 250-280pc, much closer than the Orion A cloud and similar to distance estimates of {kappa} Ori. We propose that the ring is a 5-8pc diameter shell that has been swept up by {kappa} Ori. This ring contains several groups of stars detected by Spitzer and WISE including one surrounding the Herbig Ae/Be stars V1818 Ori. In this interpretation, the {kappa} Ori ring is one of several shells swept up by massive stars within the Orion Eridanus Superbubble and is unrelated to the southern portion of OrionA/L1641S.
- ID:
- ivo://CDS.VizieR/J/ApJ/821/54
- Title:
- XMM spectral analysis of Draco dSph
- Short Name:
- J/ApJ/821/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the spectral analysis of an 87ks XMM-Newton observation of Draco, a nearby dwarf spheroidal galaxy. Of the approximately 35 robust X-ray source detections, we focus our attention on the brightest of these sources, for which we report X-ray and multiwavelength parameters. While most of the sources exhibit properties consistent with active galactic nuclei, few of them possess the characteristics of low-mass X-ray binaries (LMXBs) and cataclysmic variable (CVs). Our analysis places constraints on the population of X-ray sources with LX>3x10^33^erg/s in Draco, suggesting that there are no actively accreting black hole and neutron star binaries. However, we find four sources that could be quiescent state LMXBs/CVs associated with Draco. We also place constraints on the central black hole luminosity and on a dark matter decay signal around 3.5keV.
- ID:
- ivo://CDS.VizieR/J/MNRAS/372/661
- Title:
- XMM view of NGC 6231: OB stars
- Short Name:
- J/MNRAS/372/661
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this second paper of the series, we focus on the X-ray properties of the OB star population of NGC 6231. As a tool for our analysis, we performed a literature-based census of the OB stars in the field of view. More than one hundred objects are found, among which 30% can be associated with an X-ray source. All the O-type stars are detected in the X-ray domain as soft and reasonably strong emitters. [...] Among B-type stars, the detection rate is only about 25% in the sub-type range B0-B4 and remains mostly uniform throughout the different sub-populations while it drops significantly at later sub-types. The associated X-ray spectra are harder than those of O-type stars. Our analysis points towards the emission being rather associated with a physical (in a multiple system) PMS companion. However, we still observe a correlation between the bolometric luminosity of the B stars and the measured X-ray luminosity. [...]
- ID:
- ivo://CDS.VizieR/J/A+A/454/1047
- Title:
- XMM view of NGC 6231 open cluster
- Short Name:
- J/A+A/454/1047
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an X-ray campaign towards the young open cluster NGC 6231. The XMM-Newton observations, of a total duration of about 180 ks, reveals that NGC 6231 is very rich in the X-ray domain too. Indeed, 610 X-ray sources are detected in the present field of view, centered on the cluster core. The limiting sensitivity of our survey is approximately 610^-15^erg/s/cm^2^ but clearly depends on the location in the field of view and on the source spectrum. Using different existing catalogues, over 85% of the X-ray sources could be associated with at least one optical and/or infrared counterpart within a limited cross-correlation radius of 2.5 or 3-arcsec according to the optical/IR catalogue used. The surface density distribution of the X-ray sources presents a slight N-S elongation. Once corrected for the spatial sensitivity variation of the EPIC instruments, the radial profile of the source surface density is well described by a King profile with a central density of about 8 sources per arcmin^2^ and a core radius close to 3.1-arcmin. The distribution of the X-ray sources seems closely related to the optical source distribution. The expected number of foreground and background sources should represent about 9% of the detected sources, thus strongly suggesting that most of the observed X-ray emitters are physically belonging to NGC 6231. Finally, beside a few bright but soft objects -- corresponding to the early-type stars of the cluster -- most of the sources are relatively faint (~5x10^-15^erg/s/cm^2^) with an energy distribution peaked around 1.0-2.0keV.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/166
- Title:
- X-ray and infra-red study of RCW 38
- Short Name:
- J/ApJ/743/166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the structure of the high-mass star-forming region RCW 38 and the spatial distribution of its young stellar population. Spitzer Infrared Array Camera (IRAC) photometry (3-8um) is combined with Two Micron All Sky Survey near-IR data to identify young stellar objects (YSOs) by IR-excess emission from their circumstellar material. Chandra X-ray data are used to identify class III pre-main-sequence stars lacking circumstellar material. We identify 624 YSOs: 23 class 0/I and 90 flat spectrum protostars, 437 class II stars, and 74 class III stars. We also identify 29 (27 new) O star candidates over the IRAC field. Seventy-two stars exhibit IR-variability, including 7 class 0/I and 12 flat spectrum YSOs. A further 177 tentative candidates are identified by their location in the IRAC [3.6] versus [3.6]-[5.8] color-magnitude diagram. We find strong evidence of subclustering in the region.
- ID:
- ivo://CDS.VizieR/J/ApJ/715/671
- Title:
- X-ray and IR emission from YSOs
- Short Name:
- J/ApJ/715/671
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a multiwavelength study of a partially embedded region of star formation centered on the Herbig Be star LkH{alpha} 101. Using two 40ks Chandra observations, we detect 213 X-ray sources in the ~17'x17' ACIS-I field. We combine the X-ray data with Two Micron All Sky Survey near-IR observations and Spitzer IRAC and MIPS 24um observations to obtain a complete picture of the cluster. A total of 158 of the X-ray sources have infrared counterparts. Of these, we find nine protostars, 48 Class II objects, five transition objects, and 72 Class III objects. From the Spitzer data we identify an additional 10 protostars, 53 Class II objects, and four transition disk candidates which are not detected by Chandra. We obtained optical spectra of a sample of both X-ray-detected and non-X-ray-detected objects. Combining the X-ray, Spitzer, and spectral data, we obtain independent estimates of cluster distance and the total cluster size -excluding protostars. We obtain consistent distance estimates of 510^+100^_-40_pc and a total cluster size of 255^+50^_-25_ stars. We find the Class II:III ratio is about 5:7 with some evidence that the Class III sources are spatially more dispersed. The cluster appears very young with three sites of active star formation and a median age of about 1Myr.
- ID:
- ivo://CDS.VizieR/J/AJ/135/693
- Title:
- X-ray and IR sources in RCW 108
- Short Name:
- J/AJ/135/693
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the results of an approximately 90ks Chandra observation of a complex region that hosts multiple sites of recent and active star formation in ARA OB1a. The field is centered on the embedded cluster RCW 108-IR and includes a large portion of the open cluster NGC 6193. We detect over 420 X-ray sources in the field and combined these data with deep near-IR, Spitzer/IRAC and Midcourse Space Experiment (MSX) mid-IR data. We find about 360 of the X-ray sources have near-IR counterparts. We divide the region into five parts based on the X-ray point source characteristics and extended 8um emission. The most clearly defined regions are the central region, identified by embedded sources with high luminosities in both the near-IR and X-ray as well as high X-ray temperatures (~3keV), and the eastern region, identified by low extinction and ~1keV X-ray temperatures. The cluster members range in X-ray luminosity from 10^29^ to 10^33^erg/s. Over 18% of the cluster members with over 100 counts exhibit flares. All sources with over 350 counts are variable. Overall about 10% (16% in RCW 108-IR) appear to have optically thick disks as derived from their position in the (J-H), (H-K) diagram. The disk fraction becomes much higher when IRAC data are employed. We fit the bulk of the X-ray spectra as absorbed Raymond-Smith-type plasmas, and find that the column to the RCW 108-IR members varies from 10^21^ to 10^23^cm^-2^. We find that the field contains 41 candidate O or B stars, and estimate that the total number of pre-main-sequence stars in the field is about 1600+/-200.
- ID:
- ivo://CDS.VizieR/J/MNRAS/429/775
- Title:
- X-ray and mid-IR study of NGC 2023
- Short Name:
- J/MNRAS/429/775
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results obtained in the X-ray and infrared study in the star-forming region NGC2023. The X-ray observation (ID=0112640201) was performed as a single 30ks exposure on 2002. Afer our processing, the useful exposure time was reduced around to 15ks. Spitzer photometry (AORKEY 8773120 and 8773632) we used MOPEX to create the mosaic image and DAOPHOT package to derived the fluxes. Optical photometry (V and I magnitude) was obtained from DENIS and Mid-Infrared from 2MASS and WISE. We used Robitaille et al. (2007ApJS..169..328R) to SED fitting and derived stellar parameters.
- ID:
- ivo://CDS.VizieR/J/ApJ/688/418
- Title:
- X-ray flares in Orion young stars. I.
- Short Name:
- J/ApJ/688/418
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Pre-main-sequence (PMS) stars are known to produce powerful X-ray flares, which resemble magnetic reconnection solar flares scaled by factors up to 104. However, there are numerous puzzles, including the structure of X-ray-emitting coronae and magnetospheres, the effects of protoplanetary disks, and the effects of stellar rotation. To investigate these issues in detail, we examine 216 of the brightest flares from 161 PMS stars observed in the Chandra Orion Ultradeep Project (COUP, Getman et al. Cat. J/ApJS/160/319). The current study (Paper I) examines the flare morphologies, and provides a general comparison of COUP flare characteristics with those of other active X-ray stars and the Sun.
3617. X-ray imaging of RCW 49
- ID:
- ivo://CDS.VizieR/J/ApJ/665/719
- Title:
- X-ray imaging of RCW 49
- Short Name:
- J/ApJ/665/719
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a high-resolution X-ray imaging study of the stellar population in the Galactic massive star-forming region RCW 49 and its central OB association Westerlund 2. We obtained a ~40ks X-ray image of a ~17'x17' field using the Chandra X-Ray Observatory and deep NIR images using the Infrared Survey Facility in a concentric ~8.3'x8.3' region. We detected 468 X-ray sources and identified optical, NIR, and Spitzer MIR counterparts for 379 of them.
- ID:
- ivo://CDS.VizieR/J/ApJ/876/50
- Title:
- X-ray & MIR AGNs in Stripe 82 with eBOSS spectra
- Short Name:
- J/ApJ/876/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a Sloan Digital Sky Survey IV eBOSS program to target X-ray sources and mid-infrared-selected Wide-field Infrared Survey Explorer (WISE) active galactic nucleus (AGN) candidates in a 36.8deg^2^ region of Stripe 82. About half this survey (15.6deg^2^) covers the largest contiguous portion of the Stripe 82 X-ray survey. This program represents the largest spectroscopic survey of AGN candidates selected solely by their WISE colors. We combine this sample with X-ray and WISE AGNs in the field identified via other sources of spectroscopy, producing a catalog of 4847 sources that is 82% complete to r~22. Based on X-ray luminosities or WISE colors, 4730 of these sources are AGNs, with a median sample redshift of z~1. About 30% of the AGNs are optically obscured (i.e., lack broad lines in their optical spectra). BPT analysis, however, indicates that 50% of the WISE AGNs at z<0.5 have emission line ratios consistent with star-forming galaxies, so whether they are buried AGNs or star-forming galaxy contaminants is currently unclear. We find that 61% of X-ray AGNs are not selected as mid-infrared AGNs, with 22% of X-ray AGNs undetected by WISE. Most of these latter AGNs have high X-ray luminosities (Lx>10^44^erg/s), indicating that mid-infrared selection misses a sizable fraction of the highest luminosity AGNs, as well as lower luminosity sources where AGN-heated dust is not dominating the mid-infrared emission. Conversely, ~58% of WISE AGNs are undetected by X-rays, though we do not find that they are preferentially redder than the X-ray-detected WISE AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/161
- Title:
- X-ray obs. and membership probabilities of M37
- Short Name:
- J/ApJ/809/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Empirical calibrations of the stellar age-rotation-activity relation (ARAR) rely on observations of the co-eval populations of stars in open clusters. We used the Chandra X-ray Observatory to study M37, a 500-Myr-old open cluster that has been extensively surveyed for rotation periods (P_rot_). M37 was observed almost continuously for five days, for a total of 440.5ks, to measure stellar X-ray luminosities (L_X_), a proxy for coronal activity, across a wide range of masses. The cluster's membership catalog was revisited to calculate updated membership probabilities from photometric data and each star's distance to the cluster center. The result is a comprehensive sample of 1699 M37 members: 426 with P_rot_, 278 with X-ray detections, and 76 with both. We calculate Rossby numbers, R_0_=P_rot_/{tau}, where {tau} is the convective turnover time, and ratios of the X-ray-to-bolometric luminosity, L_X_/L_bol_, to minimize mass dependencies in our characterization of the rotation-coronal activity relation at 500Myr. We find that fast rotators, for which R_0_<0.09+/-0.01, show saturated levels of activity, with log(L_X_/L_bol_)=-3.06+/-0.04. For R_0_>=0.09+/-0.01, activity is unsaturated and follows a power law of the form R_0_^{beta}^, where {beta}=-2.03^+0.17^_-1.14_. This is the largest sample available for analyzing the dependence of coronal emission on rotation for a single-aged population, covering stellar masses in the range 0.4-1.3M_{sun}_, P_rot_ in the range 0.4-12.8 days, and L_X_ in the range 10^28.4-30.5^erg/s. Our results make M37 a new benchmark open cluster for calibrating the ARAR at ages of ~500Myr.
- ID:
- ivo://CDS.VizieR/J/AJ/134/999
- Title:
- X-ray observations of NGC 2264
- Short Name:
- J/AJ/134/999
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from an X-ray imaging survey of the young cluster NGC 2264, carried out with the European Photon Imaging Cameras (EPIC) on board the XMM-Newton spacecraft. The X-ray data are merged with extant optical and near-infrared photometry, spectral classifications, Halpha emission strengths, and rotation periods to examine the interrelationships between coronal and chromospheric activity, rotation, stellar mass, and internal structure for a statistically significant sample of pre-main-sequence stars. A total of 300 distinct X-ray sources can be identified with optical or near-infrared counterparts. The sources are concentrated within three regions of the cluster: in the vicinity of S Mon, within the large emission/reflection nebulosity southwest of S Mon, and along the broad ridge of molecular gas that extends from the Cone Nebula to the NGC 2264 IRS 2 field.
- ID:
- ivo://CDS.VizieR/J/ApJ/734/43
- Title:
- X-ray, optical and radio monitoring of 3C 111
- Short Name:
- J/ApJ/734/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 111 between 2004 and 2010 at X-ray (2.4-10keV), optical (R band), and radio (14.5, 37, and 230GHz) wave bands, as well as multi-epoch imaging with the Very Long Baseline Array (VLBA) at 43GHz. Over the six years of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. This shows a clear connection between the radiative state near the black hole, where the X-rays are produced, and events in the jet. The X-ray continuum flux and Fe line intensity are strongly correlated, with a time lag shorter than 90 days and consistent with zero.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/1777
- Title:
- X-ray properties of 3 EDisCS galaxy clusters
- Short Name:
- J/MNRAS/371/1777
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present XMM-Newton observations of three optically selected z>0.6 clusters from the European Southern Observatory (ESO) Distant Cluster Survey (EDisCS), comprising the first results of a planned X-ray survey of the full EDisCS high-redshift sample. The EDisCS clusters were identified in the Las Campanas Distant Cluster Survey as surface brightness fluctuations in the optical sky and their masses and galaxy populations are well described by extensive photometric and spectroscopic observations. We detect two of the three clusters in the X-ray and place a firm upper limit on diffuse emission in the third cluster field. We are able to constrain the X-ray luminosity and temperature of the detected clusters and estimate their masses. We find that the X-ray properties of the detected EDisCS clusters are similar to those of X-ray-selected clusters of comparable mass and --- unlike other high-redshift, optically selected clusters --- are consistent with the T-sigma and L_X_-sigma relations determined from X-ray-selected clusters at low redshift. The X-ray determined mass estimates are generally consistent with those derived from weak-lensing and spectroscopic analyses. These preliminary results suggest that the novel method of optical selection used to construct the EDisCS catalogue may, like selection by X-ray luminosity, be well suited for identification of relaxed, high-redshift clusters whose intracluster medium is in place and stable by z=0.8.
- ID:
- ivo://CDS.VizieR/J/ApJ/677/401
- Title:
- Xray properties of protostars in ONC
- Short Name:
- J/ApJ/677/401
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin and evolution of the X-ray emission in very young stellar objects (YSOs) are not yet well understood because it is very hard to observe YSOs in the protostellar phase. Using COUP data, we study the X-ray properties of stars in the ONC in different evolutionary classes: luminosities, hydrogen column densities N_H_, effective plasma temperatures, and time variability are compared to understand if the interaction between the circumstellar material and the central object can influence the X-ray emission. We have assembled the deepest and most complete photometric catalog of objects in the ONC region from the UV to 8um using data from the HST Treasury Program; deep and almost simultaneous UBVI and JHK images taken, respectively, with WFI at ESO 2.2m and ISPI at CTIO 4m telescopes; and Spitzer IRAC imaging. We select high-probability candidate Class 0-I protostars, a sample of "bona fide" Class II stars, and a set of Class III stars with IR emission consistent with normal photospheres. Our principal result is that Class 0-Ia objects are significantly less luminous in X-rays, in both the total and hard bands, than the more evolved Class II stars with mass larger than 0.5M_{sun}_; the latter show X-ray luminosities similar to those of Class 0-Ib stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/2485
- Title:
- X-rays from the star-forming complex W40
- Short Name:
- J/ApJ/725/2485
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young stellar cluster illuminating the W40 HII region, one of the nearest massive star-forming regions, has been observed with the ACIS detector on board the Chandra X-ray Observatory. Due to its high obscuration, this is a poorly studied stellar cluster with only a handful of bright stars visible in the optical band, including three OB stars identified as primary excitation sources. We detect 225 X-ray sources, of which 85% are confidently identified as young stellar members of the region. Two potential distances of the cluster, 260pc and 600pc, are used in the paper.
3625. X-ray sources in CMa OB1
- ID:
- ivo://CDS.VizieR/J/A+A/609/A127
- Title:
- X-ray sources in CMa OB1
- Short Name:
- J/A+A/609/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Canis Major OB1 association has an intriguing scenario of star formation, especially in the region called Canis Major R1 (CMa R1) traditionally assigned to a reflection nebula, but in reality an ionized region. This work is focussed on the young stellar population associated with CMa R1, for which our previous results from ROSAT, optical, and near-infrared data had revealed two stellar groups with different ages, suggesting a possible mixing of populations originated from distinct star formation episodes. The X-ray data allow the detected sources to be characterized according to hardness ratios, light curves, and spectra. Estimates of mass and age were obtained from the 2MASS catalogue and used to define a complete subsample of stellar counterparts for statistical purposes. A catalogue of 387 XMM-Newton sources is provided, of which 78% are confirmed as members or probable members of the CMa R1 association. Flares (or similar events) were observed for 13 sources and the spectra of 21 bright sources could be fitted by a thermal plasma model. Mean values of fits parameters were used to estimate X-ray luminosities. We found a minimum value of log(L_X_[erg/s])=29.43, indicating that our sample of low-mass stars (M*<=0.5 M_{sun}_), which are faint X-ray emitters, is incomplete. Among the 250 objects selected as our complete subsample (defining our "best sample"), 171 are found to the east of the cloud, near Z CMa and dense molecular gas, of which 50% of them are young (<5Myr) and 30% are older (>10Myr). The opposite happens to the west, near GU CMa, in areas lacking molecular gas: among 79 objects, 30% are young and 50% are older. These findings confirm that a first episode of distributed star formation occurred in the whole studied region ~10Myr ago and dispersed the molecular gas, while a second, localized episode (<5Myr) took place in the regions where molecular gas is still present.
- ID:
- ivo://CDS.VizieR/J/ApJS/184/84
- Title:
- X-ray sources in Cyg OB2 region
- Short Name:
- J/ApJS/184/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of 1696 X-ray sources detected in the massive star forming region (SFR) Cygnus OB2 and extracted from two archival Chandra observations of the center of the region. A deep source extraction routine, exploiting the low background rates of Chandra observations was employed to maximize the number of sources extracted. Observations at other wavelengths were used to identify low count-rate sources and remove likely spurious sources. Monte Carlo simulations were also used to assess the authenticity of these sources. X-ray spectra were fitted with thermal plasma models to characterize the objects and X-ray light curves were analyzed to determine their variability. We used a Bayesian technique to identify optical or near-IR counterparts for 1501 (89%) of our sources, using deep observations from the INT Photometric H-alpha Survey, the Two Micron All Sky Survey, and the UKIRT Infrared Deep Sky Survey-Galactic plane Survey. 755 (45%) of these objects have six-band r', H-alpha, i', J, H, and K optical and near-IR photometry. From an analysis of the Poisson false-source probabilities for each source we estimate that our X-ray catalogue includes <1% of false sources, and an even lower fraction when only sources with optical or near-IR associations are considered. A Monte Carlo simulation of the Bayesian matching scheme allows this method to be compared to more simplified matching techniques and enables the various sources of error to be quantified. The catalogue of 1696 objects presented here includes X-ray broad band fluxes, model fits, and optical and near-IR photometry in what is one of the largest X-ray catalogue of a single SFR to date. The high number of stellar X-ray sources detected from relatively shallow observations confirms the status and importance of Cygnus OB2 as one of our Galaxy's most massive SFRs.
- ID:
- ivo://CDS.VizieR/J/ApJ/654/316
- Title:
- X-ray sources in IC 1396N
- Short Name:
- J/ApJ/654/316
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The IC 1396N cometary globule (CG) within the large nearby HII region IC 1396 has been observed with the ACIS detector on board the Chandra X-Ray Observatory. We detect 117 X-ray sources, of which ~50-60 are likely members of the young open cluster Trumpler 37 dispersed throughout the HII region, and 25 are associated with young stars formed within the globule. Infrared photometry (2MASS and Spitzer) shows that the X-ray population is very young: 3 older Class III stars, 16 classical T Tauri stars, and 6 protostars including a Class 0/I system.
3628. X-ray sources in NGC 752
- ID:
- ivo://CDS.VizieR/J/A+A/490/113
- Title:
- X-ray sources in NGC 752
- Short Name:
- J/A+A/490/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- While observational evidence shows that most of the decline in a star's X-ray activity occurs between the age of the Hyades (~8x10^8yr) and that of the Sun, very little is known about the evolution of stellar activity between these ages. To gain information on the typical level of coronal activity at a star's intermediate age, we studied the X-ray emission from stars in the 1.9Gyr old open cluster NGC 752. We analysed a ~140ks Chandraobservation of NGC 752 and a ~50ks XMM-Newtonobservation of the same cluster. We detected 262 X-ray sources in the Chandra data and 145 sources in the XMM-Newton observation. Around 90% of the catalogued cluster members within Chandra's field-of-view are detected in the X-ray. The X-ray luminosity of all observed cluster members (28 stars) and of 11 cluster member candidates was derived.
- ID:
- ivo://CDS.VizieR/J/AJ/162/92
- Title:
- 126 X-rays sources around the cepheid {eta} Aql
- Short Name:
- J/AJ/162/92
- Date:
- 14 Mar 2022 07:02:20
- Publisher:
- CDS
- Description:
- X-ray bursts have recently been discovered in the Cepheids {delta}Cep and {beta}Dor modulated by the pulsation cycle. We have obtained an observation of the Cepheid {eta}Aql with the XMM-Newton satellite at the phase of maximum radius; the phase at which there is a burst of X-rays in {delta}Cep. No X-rays were seen from the Cepheid {eta}Aql at this phase, and the implications for Cepheid upper atmospheres are discussed. We have also used the combination of X-ray sources, as well as Gaia and 2MASS data, to search for a possible grouping around the young intermediate mass Cepheid. No indication of such a group was found.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/2917
- Title:
- X-rays sources in Trumpler 37
- Short Name:
- J/MNRAS/426/2917
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rich young stellar clusters produce HII regions whose expansion into the nearby molecular cloud is thought to trigger the formation of new stars. However, the importance of this mode of star formation is uncertain. This investigation seeks to quantify triggered star formation (TSF) in IC 1396A (aka the Elephant Trunk Nebula), a bright-rimmed cloud (BRC) on the periphery of the nearby giant HII region IC 1396 produced by the Trumpler 37 cluster. X-ray selection of young stars from Chandra X-ray Observatory data is combined with existing optical and infrared surveys to give a more complete census of the TSF population. Over 250 young stars in and around IC 1396A are identified; this doubles the previously known population. A spatio-temporal gradient of stars from the IC 1396A cloud towards the primary ionizing star HD 206267 is found.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/99
- Title:
- X-ray survey of YSOs in Orion A
- Short Name:
- J/ApJ/768/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an XMM-Newton survey of the part of the Orion A cloud south of the Orion Nebula. This survey includes the Lynds 1641 (L1641) dark cloud, a region of the Orion A cloud with very few massive stars and hence a relatively low ambient UV flux, and the region around the O9III star {iota} Orionis. In addition to proprietary data, we used archival XMM data of the Orion Nebula Cluster (ONC) to extend our analysis to a major fraction of the Orion A cloud. We have detected 1060 X-ray sources in L1641 and the {iota} Ori region. About 94% of the sources have Two Micron All Sky Survey and Spitzer counterparts, 204 and 23 being Class II and Class I or protostar objects, respectively. In addition, we have identified 489 X-ray sources as counterparts to Class III candidates, given they are bright in X-rays and appear as normal photospheres at mid-IR wavelengths. The remaining 205 X-ray sources are likely distant active galactic nuclei or other galactic sources not related to Orion A. We find that Class III candidates appear more concentrated in two main clusters in L1641. The first cluster of Class III stars is found toward the northern part of L1641, concentrated around {iota} Ori. The stars in this cluster are more evolved than those in the Orion Nebula. We estimate a distance of 300-320 pc for this cluster showing that it is in the foreground of the Orion A cloud. Another cluster rich in Class III stars is located in L1641 South and appears to be a slightly older cluster embedded in the Orion A cloud. Furthermore, other evolved Class III stars are found north of the ONC toward NGC 1977.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/48
- Title:
- X-ray through NIR photometry of NGC 2617
- Short Name:
- J/ApJ/788/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- After the All-Sky Automated Survey for SuperNovae discovered a significant brightening of the inner region of NGC 2617, we began a ~70 day photometric and spectroscopic monitoring campaign from the X-ray through near-infrared (NIR) wavelengths. We report that NGC 2617 went through a dramatic outburst, during which its X-ray flux increased by over an order of magnitude followed by an increase of its optical/ultraviolet (UV) continuum flux by almost an order of magnitude. NGC 2617, classified as a Seyfert 1.8 galaxy in 2003, is now a Seyfert 1 due to the appearance of broad optical emission lines and a continuum blue bump. Such "changing look active galactic nuclei (AGNs)" are rare and provide us with important insights about AGN physics. Based on the H{beta} line width and the radius-luminosity relation, we estimate the mass of central black hole (BH) to be (4+/-1)x10^7^ M_{sun}_. When we cross-correlate the light curves, we find that the disk emission lags the X-rays, with the lag becoming longer as we move from the UV (2-3 days) to the NIR (6-9 days). Also, the NIR is more heavily temporally smoothed than the UV. This can largely be explained by a simple model of a thermally emitting thin disk around a BH of the estimated mass that is illuminated by the observed, variable X-ray fluxes.
3633. XX Cep BVRI light curves
- ID:
- ivo://CDS.VizieR/J/MNRAS/379/1665
- Title:
- XX Cep BVRI light curves
- Short Name:
- J/MNRAS/379/1665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained CCD photometric observations of the Algol-type semidetached binary XX Cephei (XX Cep) during 15 nights from 2002 September 17 to 2003 February 2, and also on 2005 January 21. Except for those data taken on the last night of the concentrated observing season, the 3881 measurements were obtained over an interval of only 106 nights. From these data, four new times of minimum light were calculated. The (O-C) diagram formed from all available timings, and thus the orbital period of the system, can be partly represented as a beat effect between two cyclical variations with different periods (P1'=42yr, P2'=181yr) and amplitudes (K1=0.015d, K2=0.103d), respectively. Both physical and non-physical interpretations of these cycles were investigated.
3634. XXL Survey. DR2
- ID:
- ivo://CDS.VizieR/IX/52
- Title:
- XXL Survey. DR2
- Short Name:
- IX/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the second data release (DR2) of the XXL Survey, contextually with the appearance of a second A&A special issue dedicated to XXL. This intermediate release includes the following catalogues and data: The X-ray point source catalogue (3XLSS) and the associated multiwavelength catalogues in the XXL-N and XXL-s areas (XXL paper XXVII). The same paper also provides the list of XMM pointings used, and a supplementary catalogue of redshifts obtained with the AAOmega spectrograph in the XXL-S area. The XXL-365-GC galaxy cluster catalogue (XXL paper XX) with the complete subset of clusters for which the selection function is well determined plus all X-ray clusters which are, to date, spectroscopically confirmed. The ATCA 2.1 GHz radio source catalogue in the XXL-S area (XXL paper XXVIII), together with the catalogue of ther optical and near infrared counterparts (XXL paper XXVI). The GMRT 610 MHz radio source catalogue in the XXL-N area (XXL paper XXIX). FITS images of the XXL-North field: continuum radio mosaic from observations with the Giant Meterwave Radio Telescope (GMRT) at 610MHz, and the corresponding noise map. A complete spectrophotometric sample of galaxies within X-ray detected, optically spectroscopically confirmed groups and clusters (G&C), including also field objects, in the XXL-N area (XXL paper XXII). The list of brightest cluster galaxies (BCGs) in the XXL-N area (XXL paper XXVIII). FITS images of the two radio galaxies described in XXL paper XXXIV. ATCA XXL-S source classification data (XXL paper XXXVI) http://sci.esa.int/xmm-newton/60686-tracing-the-universe-x-ray-survey-\ supports-standard-cosmological-model/ List of XXL DR2 papers: XVI. The clustering of X-ray selected galaxy clusters at z~0.3 XVII. X-ray and Sunyaev-Zel'dovich properties of the redshift 2.0 galaxy cluster XLSSC 122 XVIII. ATCA 2.1 GHz radio source catalogue and source counts for the XXL-South field XIX. A realistic population of simulated X-ray AGN: Comparison of models with observations XX. The 365 cluster catalogue XXI. The environment and clustering of X-ray AGN in the XXL-South field XXII. The XXL-North spectrophotometric sample and galaxy stellar mass function in X-ray detected groups and clusters XXIII. The mass scale of XXL clusters from ensemble spectroscopy XXIV. The final detection pipeline XXV. Cosmological analysis of the C1 cluster number counts XXVI. Optical and near infrared identification of the ATCA 2.1 GHz radio sources in the XXL-S field XXVII. The 3XLSS point source catalogue XXVIII. Galaxy luminosity functions of the XXL-N clusters XXIX. GMRT 610 MHz continuum observations XXX. Characterisation of the XLSSsC N01 supercluster and analysis of the galaxy stellar populations XXXI. Classification and host galaxy properties of 2.1 GHz ATCA XXL-S radio sources XXXII. Spatial clustering of the XXL-S AGN XXXIII. Chandra constraints on the AGN contamination of z > 1 XXL galaxy clusters XXXIV. Double irony in XXL-North. A tale of two radio galaxies in a supercluster at z = 0.14 XXXV. The role of cluster mass in AGN activity XXXVI. Evolution and black hole feedback of high-excitation and low-excitation radio galaxies in XXL-S
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/1517
- Title:
- XY And and UZ Vir light curves
- Short Name:
- J/MNRAS/427/1517
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a thorough analysis of multicolour CCD observations of two modulated RRab-type variables, XY And and UZ Vir. These Blazhko stars show relatively simple light-curve modulation with the usual multiplet structures in their Fourier spectra. One additional, independent frequency with linear-combination terms of the pulsation frequency is also detected in the residual spectrum of each of the two stars. The amplitude and phase relations of the triplet components are studied in detail. Most of the epoch-independent phase differences show a slight, systematic colour dependence. However, these trends have opposite signs in the two stars. The mean values of the global physical parameters and their changes with the Blazhko phase are determined, utilizing the inverse photometric method (IPM). The modulation properties and the IPM results are compared for the two variables. The pulsation period of XY And is the shortest when its pulsation amplitude is the highest, while UZ Vir has the longest pulsation period at this phase of the modulation. Despite this contrasting behaviour, the phase relations of the variations in their mean physical parameters are similar. These results do not agree with the predictions of the Blazhko model of Stothers.
3636. XY UMa BVRI light curves
- ID:
- ivo://CDS.VizieR/J/AJ/139/1801
- Title:
- XY UMa BVRI light curves
- Short Name:
- J/AJ/139/1801
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New CCD photometric observations of the chromospherically active binary XY Ursae Majoris (XY UMa) were obtained every year since 2006. The light curves obtained in the late Spring of 2006 show obvious variations on a short timescale, while the light curves obtained in 2008 December do not. But both sets of light curves are markedly asymmetric, and were analyzed using the 2003 version of the Wilson-Devinney code with spot model. New absolute physical parameters are obtained.
- ID:
- ivo://CDS.VizieR/J/A+A/563/A120
- Title:
- Y Cyg light curves and time of minima
- Short Name:
- J/A+A/563/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rapid advancements in light-curve and radial-velocity curve modelling, as well as improvements in the accuracy of observations, allow more stringent tests of the theory of stellar evolution. Binaries with rapid apsidal advance are particularly useful in this respect since the internal structure of the stars can also be tested. Thanks to its long and rich observational history and rapid apsidal motion, the massive eclipsing binary Y Cyg represents one of the cornerstones of critical tests of stellar evolutionary theory for massive stars. Nevertheless, the determination of the basic physical properties is less accurate than it could be given the existing number of spectral and photometric observations. Our goal is to analyse all these data simultaneously with the new dedicated series of our own spectral and photometric observations from observatories widely separated in longitude.
- ID:
- ivo://CDS.VizieR/J/ApJS/190/203
- Title:
- 3.6 years of DIRBE NIR stellar light curves
- Short Name:
- J/ApJS/190/203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The weekly averaged near-infrared fluxes for 2652 stars were extracted from the cold and warm era all-sky maps of the Diffuse Infrared Background Experiment (DIRBE). Since the DIRBE program only archived the individual Calibrated Infrared Observations for the 10 month cold era mission, the weekly averaged fluxes were all that were available for the warm era. The steps required to extract stellar fluxes are described as are the adjustments that were necessary to correct the results for several systematic effects. The observations are at a cadence of once a week for 3.6 years (~1300 days), providing continuous sampling on variable stars that span the entire period for the longest fundamental pulsators. The stars are divided into three categories: those with large amplitude of variability, smaller amplitude variables, and sources whose near-infrared brightness do not vary according to our classification criteria. We show examples of the results and the value of the added baseline in determining the phase lag between the visible and infrared.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/38
- Title:
- 25-years photometry of V1057 Cygni
- Short Name:
- J/MNRAS/434/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The FU Orionis type of variable star (FUor), V1057 Cygni, underwent a nova-like outburst in 1969-1970. Among the FUors, V1057 Cyg is notable for having the most dramatic post-maximum decrease in brightness. Thus, photometric monitoring of this object is important for interpretations of the cause of this event. Here, we study the behaviour of V1057 Cyg over the last 25 years on the basis of our optical and infrared observations. The optical and near-infrared observations of V1057 Cyg started in 1974, and we present all our data (up to the end of 2011), including 1085 and 167 nights of optical and infrared photometry, respectively. The UBVRIJHKLM light curves for 1985-2011 show that despite the increased photometric activity, after a rapid decrease in brightness in the mid-1990s, the average level of brightness remained practically constant. After the object becomes fainter than V~11.5mag, a swerve appears in the track of the colour-magnitude diagram. The light variability shows a different periodicity in different spectral regions. We have discovered a period of 1631+/-60d in the BVR bands (1995-2011) and 523+/-40d in the RIJHK bands (2002-2011) with amplitudes of 0.5-0.3mag. The 523-d period is presumably correlated with the changes in the radial velocity of an emission component in LiI. We conclude that the observed properties of the FUor star V1057 Cyg are in accordance with current models of FUors involving binary or multiple systems.
- ID:
- ivo://CDS.VizieR/J/AJ/159/266
- Title:
- 12 years positional measurements of 8 binaries
- Short Name:
- J/AJ/159/266
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The orbits of eight systems with low-mass components (HIP14524, HIP16025, HIP28671, HIP46199, HIP47791, HIP60444, HIP61100, and HIP73085) are presented. Speckle interferometric data were obtained at the 6m Big Telescope Alt-azimuth Special Astrophysical Observatory of the Russian Academy of Sciences (BTA SAO RAS) from 2007 to 2019. New data, together with measures already in the literature, made it possible to improve upon previous orbital solutions in six cases and to construct orbits for the first time in the two remaining cases (HIP14524 and HIP60444). Mass sums are obtained using both Hipparcos and Gaia parallaxes, and a comparison with previously published values is made. Using the Worley & Heintz criteria, the classification of the orbits constructed is carried out.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/1345
- Title:
- YJK for Type Ia supernovae
- Short Name:
- J/MNRAS/448/1345
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Type Ia supernovae (SNe Ia) have been proposed to be much better distance indicators at near-infrared (NIR) compared to optical wavelengths - the effect of dust extinction is expected to be lower and it has been shown that SNe Ia behave more like `standard candles' at NIR wavelengths. To better understand the physical processes behind this increased uniformity, we have studied the Y, J and H-filter light curves of 91 SNe Ia from the literature. We show that the phases and luminosities of the first maximum in the NIR light curves are extremely uniform for our sample. The phase of the second maximum, the late-phase NIR luminosity and the optical light-curve shape are found to be strongly correlated, in particular more luminous SNe Ia reach the second maximum in the NIR filters at a later phase compared to fainter objects. We also find a strong correlation between the phase of the second maximum and the epoch at which the SN enters the Lira law phase in its optical colour curve (epochs ~15 to 30d after B-band maximum). The decline rate after the second maximum is very uniform in all NIR filters. We suggest that these observational parameters are linked to the nickel and iron mass in the explosion, providing evidence that the amount of nickel synthesized in the explosion is the dominating factor shaping the optical and NIR appearance of SNe Ia.
- ID:
- ivo://CDS.VizieR/J/MNRAS/472/808
- Title:
- YJKs light curves of SMC Classical Cepheids
- Short Name:
- J/MNRAS/472/808
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VISTA near-infrared YJKs survey of the Magellanic System (VMC) is collecting deep Ks-band time-series photometry of pulsating stars hosted by the two Magellanic Clouds and their connecting bridge. Here, we present Y, J, Ks light curves for a sample of 717 Small Magellanic Cloud (SMC) Classical Cepheids (CCs). These data, complemented with our previous results and V magnitude from literature, allowed us to construct a variety of period-luminosity and period-Wesenheit relationships, valid for Fundamental, First and Second Overtone pulsators. These relations provide accurate individual distances to CCs in the SMC over an area of more than 40 deg^2^. Adopting literature relations, we estimated ages and metallicities for the majority of the investigated pulsators, finding that (i) the age distribution is bimodal, with two peaks at 120+/-10 and 220+/-10Myr; (i) the more metal-rich CCs appear to be located closer to the centre of the galaxy. Our results show that the three-dimensional distribution of the CCs in the SMC is not planar but heavily elongated for more than 25-30kpc approximately in the east/north-east towards south-west direction. The young and old CCs in the SMC show a different geometric distribution. Our data support the current theoretical scenario predicting a close encounter or a direct collision between the Clouds some 200Myr ago and confirm the presence of a Counter-Bridge predicted by some models. The high-precision three-dimensional distribution of young stars presented in this paper provides a new test bed for future models exploring the formation and evolution of the Magellanic System.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/3027
- Title:
- Young and embedded clusters in Cygnus-X
- Short Name:
- J/MNRAS/458/3027
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide a new view on the Cygnus-X north complex by accessing for the first time the low mass content of young stellar populations in the region. CFHT/WIRCam camera was used to perform a deep near-IR survey of this complex, sampling stellar masses down to ~0.1M_{sun}_. Several analysis tools, including a extinction treatment developed in this work, were employed to identify and uniformly characterise a dozen unstudied young star clusters in the area. Investigation of their mass distributions in low-mass domain revealed a relatively uniform log-normal IMF with a characteristic mass of 0.32+/-0.08M_{sun}_ and mass dispersion of 0.40+/-0.06. In the high mass regime, their derived slopes showed that while the youngest clusters (age<4Myr) presented slightly shallower values with respect to the Salpeter's, our older clusters (4Myr<age<18Myr) showed IMF compliant values and a slightly denser stellar population. Although possibly evidencing a deviation from an 'universal' IMF, these results also supports a scenario where these gas dominated young clusters gradually 'build up' their IMF by accreting low-mass stars formed in their vicinity during their first ~3Myr, before the gas expulsion phase, emerging at the age of ~4Myr with a fully fledged IMF. Finally, the derived distances to these clusters confirmed the existence of at least 3 different star forming regions throughout Cygnus-X north complex, at distances of 500-900pc, 1.4-1.7kpc and 3.0kpc, and revealed evidence of a possible interaction between some of these stellar populations and the Cygnus-OB2 association.
- ID:
- ivo://CDS.VizieR/J/AJ/155/109
- Title:
- Young binaries in Ophiuchus&Upper Centaurus-Lupus
- Short Name:
- J/AJ/155/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the orbital positions and flux ratios of 17 binary and triple systems in the Ophiuchus star-forming region and the Upper Centaurus-Lupus cluster based on adaptive optics imaging at the Keck Observatory. We report the detection of visual companions in MML 50 and MML 53 for the first time, as well as the possible detection of a third component in WSB 21. For six systems in our sample, our measurements provide a second orbital position following their initial discoveries over a decade ago. For eight systems with sufficient orbital coverage, we analyze the range of orbital solutions that fit the data. Ultimately, these observations will help provide the groundwork toward measuring precise masses for these pre-main-sequence stars and understanding the distribution of orbital parameters in young multiple systems.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A29
- Title:
- Young companion candidate embedded in R CrA cloud
- Short Name:
- J/A+A/624/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Within the NaCo-ISPY exoplanet imaging program, we aim at detecting and characterizing the population of low-mass companions at wide separations (>~10AU). We observed R CrA twice with the NaCo instrument at the Very Large Telescope (VLT) in the L' filter with a one year time baseline in between. We used artificial negative signals to determine the position and brightness of the companion and the related uncertainties. The companion is detected at a separation of 196.8+/-4.5/196.6+/-5.9mas (18.7+/-1.3/18.7+/-1.4AU) and position angle of 134.7+/-0.5{deg}/133.7+/-0.7{deg} in the first/second epoch observation. We measure a contrast of 7.29+/-0.18/6.70+/-0.15mag with respect to the primary. A study of the stellar proper motion rejects the hypothesis that the signal is a background object. Depending on the assumed age, extinction, and brightness of the primary, the stellar companion has a mass between 0.10+/-0.02M_{sun}_ and 1.03^+0.20^_-0.18_M_{sun}_ range, if no contribution from circumsecondary material is taken into account. The presence of this companion needs to be taken into account when analyzing the complex circumstellar environment of R CrA.
- ID:
- ivo://CDS.VizieR/J/A+A/518/L73
- Title:
- Youngest massive protostars in the LMC
- Short Name:
- J/A+A/518/L73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We demonstrate the unique capabilities of Herschel to study very young luminous extragalactic young stellar objects (YSOs) by analyzing a central strip of the Large Magellanic Cloud obtained through the HERITAGE Science Demonstration Program. We combine PACS 100 and 160, and SPIRE 250, 350, and 500um photometry with 2MASS (1.25-2.17um) and Spitzer IRAC and MIPS (3.6-70um) to construct complete spectral energy distributions (SEDs) of compact sources. From these, we identify 207 candidate embedded YSOs in the observed region, ~40% never-before identified. We discuss their position in far-infrared color-magnitude space, comparing with previously studied, spectroscopically confirmed YSOs and maser emission. All have red colors indicating massive cool envelopes and great youth. We analyze four example YSOs, determining their physical properties by fitting their SEDs with radiative transfer models. Fitting full SEDs including the Herschel data requires us to increase the size and mass of envelopes included in the models. This implies higher accretion rates (greater or equal to 10^-4^M_{sun}_/yr), in agreement with previous outflow studies of high-mass protostars. Our results show that Herschel provides reliable longwave SEDs of large samples of high-mass YSOs; discovers the youngest YSOs whose SEDs peak in Herschel bands; and constrains the physical properties and evolutionary stages of YSOs more precisely than was previously possible.
- ID:
- ivo://CDS.VizieR/J/ApJ/726/18
- Title:
- Young intermediate-mass stars in W5
- Short Name:
- J/ApJ/726/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey of young intermediate-mass stars (age<5Myr, 1.5M_{sun}_<M*<=15M_{sun}_) in the W5 massive star-forming region. We use combined optical, near-infrared, and Spitzer Space Telescope photometry and optical spectroscopy to define a sample of stars of spectral types A and B and examine their infrared excess properties. We find objects with infrared excesses characteristic of optically thick disks, i.e., Herbig AeBe stars. These stars are rare: <1.5% of the entire spectroscopic sample of A and B stars, and absent among stars more massive than 2.4M_{sun}_. 7.5% of the A and B stars possess infrared excesses in a variety of morphologies that suggest their disks are in some transitional phase between an initial, optically thick accretion state and later evolutionary states. We identify four morphological classes based on the wavelength dependence of the observed excess emission above theoretical photospheric levels: (1) the optically thick disks; (2) disks with an optically thin excess over the wavelength range 2-24um, similar to that shown by Classical Be stars; (3) disks that are optically thin in their inner regions based on their infrared excess at 2-8um and optically thick in their outer regions based on the magnitude of the observed excess emission at 24um; (4) disks that exhibit empty inner regions (no excess emission at {lambda}<8um) and some measurable excess emission at 24um. A sub-class of disks exhibit no significant excess emission at {lambda}<=5.8um, have excess emission only in the Spitzer 8um band and no detection at 24um. We discuss these spectral energy distribution types, and suggest physical models for disks exhibiting these emission patterns and additional observations to test these theories.
- ID:
- ivo://CDS.VizieR/J/ApJ/525/466
- Title:
- Young low-mass stars and brown dwarfs in IC 348
- Short Name:
- J/ApJ/525/466
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present new results from a continuing program to identify and characterize the low-mass stellar and substellar populations in the young cluster IC 348 (0.5 - 10 Myr). Optical spectroscopy has revealed young objects with spectral types as late as M8.25. The intrinsic J-H and H-K colors of these sources are dwarflike, whereas the R-I and I-J colors appear intermediate between the colors of dwarfs and giants. Furthermore, the spectra from 6500 to 9500 {AA} are reproduced well with averages of standard dwarf and giant spectra, suggesting that such averages should be used in the classification of young late-type sources.
- ID:
- ivo://CDS.VizieR/J/A+AS/139/393
- Title:
- Young Massive Star Clusters. II.
- Short Name:
- J/A+AS/139/393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 4 lists photometric data for Young Massive Star Clusters identified in a sample of 21 nearby galaxies. The photometric data have been corrected for Galactic foreground extinction. Each cluster is identified by the abbreviated NGC number of its host galaxy and an object number: nxxx-yyy is object number yyy in the galaxy NGC xxx. Effective cluster radii have been obtained by modeling the cluster images as MOFFAT15 functions convolved with the point-spread function measured on the CCD images.
- ID:
- ivo://CDS.VizieR/J/ApJ/695/511
- Title:
- Young massive stars in LHA 120-N 44
- Short Name:
- J/ApJ/695/511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HII complex N44 in the Large Magellanic Cloud (LMC) provides an excellent site to perform a detailed study of star formation in a mild starburst, as it hosts three regions of star formation at different evolutionary stages, and it is not as complicated and confusing as the 30 Doradus giant HII region. We have obtained Spitzer Space Telescope observations and complementary ground-based 4m uBVIJK observations of N44 to identify candidate massive young stellar objects (YSOs). We further classify the YSOs into Types I, II, and III, according to their spectral energy distributions (SEDs). In our sample of 60 YSO candidates, ~65% of them are resolved into multiple components or extended sources in high-resolution ground-based images.
- ID:
- ivo://CDS.VizieR/J/A+A/507/1485
- Title:
- Young (proto)stellar population in L1630
- Short Name:
- J/A+A/507/1485
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the young (proto)stellar population in NGC 2023 and the L 1630 molecular cloud bordering the H II region IC 434, using Spitzer IRAC and MIPS archive data, JCMT SCUBA imaging and spectroscopy as well as targeted BIMA observations of one of the Class 0 protostars, NGC 2023 MM 1. We study the distribution of gas, dust and young stars in this region to see where stars are forming, whether the expansion of the H II region has triggered star formation, and whether dense cold cores have already formed stars. We have performed photometry of all IRAC and MIPS images, and used color-color diagrams to identify and classify all young stars seen within a 22'x26' field along the boundary between IC 434 and L 1630.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/124
- Title:
- Young star forming region NGC 2264 Spitzer sources
- Short Name:
- J/ApJ/794/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer 3.6, 4.5, 5.8, 8.0, and 24 {mu}m images of the Mon OB1 East giant molecular cloud, which contains the young star forming region NGC 2264, as well as more extended star formation. With Spitzer data and Two Micron All Sky Survey photometry, we identify and classify young stellar objects (YSOs) with dusty circumstellar disks and/or envelopes in Mon OB1 East by their infrared-excess emission and study their distribution with respect to cloud material. We find a correlation between the local surface density of YSOs and column density of molecular gas as traced by dust extinction that is roughly described as a power law in these quantities. NGC 2264 follows a power-law index of ~2.7, exhibiting a large YSO surface density for a given gas column density. Outside of NGC 2264 where the surface density of YSOs is lower, the power law is shallower and the region exhibits a larger gas column density for a YSO surface density, suggesting the star formation is more recent. In order to measure the fraction of cloud members with circumstellar disks/envelopes, we estimate the number of diskless pre-main-sequence stars by statistical removal of background star detections. We find that the disk fraction of the NGC 2264 region is 45%, while the surrounding, more distributed regions show a disk fraction of 19%. This may be explained by the presence of an older, more dispersed population of stars. In total, the Spitzer observations provide evidence for heterogenous, non-coeval star formation throughout the Mon OB1 cloud.
- ID:
- ivo://CDS.VizieR/J/A+A/485/931
- Title:
- Young stars and brown dwarfs in Ori OB1b
- Short Name:
- J/A+A/485/931
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present here exhaustive lists of known young stars and new candidate members around Alnilam and Mintaka in the Ori OB1b association as well as of fore- and background sources. A total of 133 stars display features of extreme youth, including early spectral types, lithium in absorption, or mid-infrared flux excess. Other two young brown dwarf and 289 star candidates have been identified from an optical/near-infrared colour-magnitude diagram. We list additional 74 known objects that might belong to the association. This compilation of tables can serve as an input for characterisation of the stellar and high-mass substellar populations in the Orion Belt.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/545
- Title:
- Young stars in Cepheus OB3b
- Short Name:
- J/MNRAS/403/545
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric study of I-band variability in the young association Cepheus OB3b. The study is sensitive to periodic variability on time-scales of less than a day, to more than 20d. After rejection of contaminating objects using V, I, R and narrow-band H{alpha} photometry, we find 475 objects with measured rotation periods, which are very likely pre-main-sequence members of the Cep OB3b star-forming region.
- ID:
- ivo://CDS.VizieR/J/AJ/130/188
- Title:
- Young stars in Trumpler 37 and NGC 7160
- Short Name:
- J/AJ/130/188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of MMT observations of young stars for our study of protoplanetary disks at ages 1-10Myr in two young clusters located in the Cepheus OB2 region: Trumpler 37 (embedded in the HII region IC 1396) and NGC 7160. Using low-resolution optical spectra from the Hectospec multifiber spectrograph, we have tripled the number of known low-mass cluster members, identifying 130 new members in Tr 37 and 30 in NGC 7160. We use indicators of youth (Li absorption at 6707{AA}) and accretion/chromospheric activity (H{alpha} emission) to identify and classify the low-mass cluster members. We derive spectral types for all the low-mass candidates and calculate the individual extinctions and the average over the clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A29
- Title:
- Young stellar clusters in the Rosette
- Short Name:
- J/A+A/557/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Rosette complex is a well studied region of the galactic plane which presents the apparent characteristics of a triggered star forming region. This is however still debated as no strong evidence corroborates this statement. We focused on characterizing the young stellar population in the Rosette to improve our understanding of the processes that regulate the star formation in this region. We propose an original method relying on the joint analysis of the star color and density in the near-infrared. It yielded the identification of 13 clusters, 2 of them being new discoveries. Based on their spectral index from UKIDSS K-band to WISE W3-band, we identified 535 YSO candidates within these cluster boundaries.
- ID:
- ivo://CDS.VizieR/J/ApJ/762/88
- Title:
- Young stellar kinematic group candidate members
- Short Name:
- J/ApJ/762/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new method based on a Bayesian analysis to identify new members of nearby young kinematic groups. The analysis minimally takes into account the position, proper motion, magnitude, and color of a star, but other observables can be readily added (e.g., radial velocity, distance). We use this method to find new young low-mass stars in the {beta} Pictoris and AB Doradus moving groups and in the TW Hydrae, Tucana-Horologium, Columba, Carina, and Argus associations. Starting from a sample of 758 mid-K to mid-M (K5V-M5V) stars showing youth indicators such as H{alpha} and X-ray emission, our analysis yields 214 new highly probable low-mass members of the kinematic groups analyzed. One is in TW Hydrae, 37 in {beta} Pictoris, 17 in Tucana-Horologium, 20 in Columba, 6 in Carina, 50 in Argus, 32 in AB Doradus, and the remaining 51 candidates are likely young but have an ambiguous membership to more than one association. The false alarm rate for new candidates is estimated to be 5% for {beta} Pictoris and TW Hydrae, 10% for Tucana-Horologium, Columba, Carina, and Argus, and 14% for AB Doradus. Our analysis confirms the membership of 58 stars proposed in the literature. Firm membership confirmation of our new candidates will require measurement of their radial velocity (predicted by our analysis), parallax, and lithium 6708{AA} equivalent width. We have initiated these follow-up observations for a number of candidates, and we have identified two stars (2MASSJ01112542+1526214, 2MASSJ05241914-1601153) as very strong candidate members of the {beta} Pictoris moving group and one strong candidate member (2MASSJ05332558-5117131) of the Tucana-Horologium association; these three stars have radial velocity measurements confirming their membership and lithium detections consistent with young age.
- ID:
- ivo://CDS.VizieR/J/AJ/159/200
- Title:
- Young stellar objects in Lupus star-forming region
- Short Name:
- J/AJ/159/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The identification and characterization of stellar members within a star-forming region are critical to many aspects of star formation, including formalization of the initial mass function, circumstellar disk evolution, and star formation history. Previous surveys of the Lupus star-forming region have identified members through infrared excess and accretion signatures. We use machine learning to identify new candidate members of Lupus based on surveys from two space-based observatories: ESA's Gaia and NASA's Spitzer. Astrometric measurements from Gaia's Data Release 2 and astrometric and photometric data from the Infrared Array Camera on the Spitzer Space Telescope, as well as from other surveys, are compiled into a catalog for the random forest (RF) classifier. The RF classifiers are tested to find the best features, membership list, non-membership identification scheme, imputation method, training set class weighting, and method of dealing with class imbalance within the data. We list 27 candidate members of the Lupus star-forming region for spectroscopic follow-up. Most of the candidates lie in Clouds V and VI, where only one confirmed member of Lupus was previously known. These clouds likely represent a slightly older population of star formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/419/1887
- Title:
- Young stellar objects in NGC 6823
- Short Name:
- J/MNRAS/419/1887
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6823 is a young open cluster that lies at a distance of ~2kpc in the Vulpecula OB1 association. Previous studies using CCD photometry and spectroscopy have identified a Trapezium system of bright O- and B-type stars at its centre, along with several massive O-, B- and A-type stars in the cluster. We present optical VRI and near-infrared JHK photometric observations, complemented with Spitzer/Infrared Array Camera archival data, with an aim to identify the young low-mass population and the disc candidates in this region. Our survey reaches down to I~22mag and K_s_~18mag. There is significant differential reddening within the cluster. We find a bimodal distribution for A_V_, with a peak at ~3mag and a broader peak at ~10mag. We have classified the sources based on the [4.5]-[8] colour, which is least affected by extinction. We find a ~20 per cent fraction of Class I/Class II young stellar objects (YSOs) in the cluster, while a large 80 per cent fraction of the sources have a Class III classification. We have made use of the INT Photometric H{alpha} Survey (IPHAS) in order to probe the strength in H{alpha} emission for this large population of Class III sources. Nearly all of the Class III objects have photospheric (r'-H{alpha}) colours, implying an absence of H{alpha} in emission. This large population of Class III sources is thus likely the extinct field star population rather than the discless YSOs in the cluster. There is a higher concentration of the Class I/II systems in the eastern region of the cluster and close to the central Trapezium. The western part of the cluster mostly contains Class III/field stars and seems devoid of disc sources. We find evidence of a pre-main-sequence population in NGC 6823, in addition to an upper main-sequence population. The pre-main-sequence population mainly consists of young disc sources with ages between ~1 and 5Myr, and at lower masses of ~0.1-0.4M_{sun}_. There may be a possible mass-dependent age spread in the cluster, with the older stars being more massive than the younger ones. The presence of young disc sources in NGC 6823 indicates similar star formation properties in the outer regions of the Galaxy as observed for young clusters in the solar neighbourhood.
- ID:
- ivo://CDS.VizieR/J/ApJ/575/354
- Title:
- Young stellar objects in the NGC 1333
- Short Name:
- J/ApJ/575/354
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 1333, a highly active star formation region within the Perseus molecular cloud complex, has been observed with the ACIS-I detector on board the Chandra X-Ray Observatory. In our image with a sensitivity limit of ~19^28^erg/s, we detect 127 X-ray sources, most with subarcsecond positional accuracy. While 32 of these sources appear to be foreground stars and extragalactic background, 95 X-ray sources are Identified with known cluster members.
- ID:
- ivo://CDS.VizieR/J/ApJ/848/97
- Title:
- Young stellar variables with KELT for K2. I.
- Short Name:
- J/ApJ/848/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the most well-studied young stellar associations, Taurus-Auriga, was observed by the extended Kepler mission, K2, in the spring of 2017. K2 Campaign 13 (C13) is a unique opportunity to study many stars in this young association at high photometric precision and cadence. Using observations from the Kilodegree Extremely Little Telescope (KELT) survey, we identify "dippers," aperiodic and periodic variables among K2 C13 target stars. This release of the KELT data provides the community with long-time baseline observations to assist in the understanding of the more exotic variables in the association. Transient-like phenomena on timescales of months to years are known characteristics in the light curves of young stellar objects, making contextual pre- and post-K2 observations critical to understanding their underlying processes. We are providing a comprehensive set of the KELT light curves for known Taurus-Auriga stars in K2 C13. The combined data sets from K2 and KELT should permit a broad array of investigations related to star formation, stellar variability, and protoplanetary environments.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/7
- Title:
- 2yr obs. of JHK variability of stars in Tr37
- Short Name:
- J/ApJ/878/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have monitored nearly a square degree in IC 1396A/Tr 37 over 21 epochs extending over 2014-2016 for sources variable in the JHK bands. In our data, 65%+/-8% of previously identified cluster members show variations, compared with <=0.3% of field stars. We identify 119 members of Tr 37 on the basis of variability, forming an unbiased sample down to the brown dwarf regime. The K-band luminosity function in Tr 37 is similar to that of IC 348 but shifted to somewhat brighter values, implying that the K- and M-type members of Tr 37 are younger than those in IC 348. We introduce methods to classify the causes of variability, based on behavior in the color-color and color-magnitude diagrams. Accretion hot spots cause larger variations at J than at K with substantial scatter in the diagrams; there are at least a dozen, with the most active resembling EXors. Eleven sources are probably dominated by intervention of dust clumps in their circumstellar disks, with color behavior indicating the presence of grains larger than for interstellar dust, presumably due to grain growth in their disks. Thirteen sources have larger variations at K than at J or H. For 11 of them, the temperature fitted to the variable component is very close to 2000K, suggesting that the changes in output are caused by turbulence at the inner rim of the circumstellar disk exposing previously protected populations of grains.
- ID:
- ivo://CDS.VizieR/J/ApJ/801/79
- Title:
- 10yr of GJ176 radial velocities & VR photometry
- Short Name:
- J/ApJ/801/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an in-depth analysis of stellar activity and its effects on radial velocity (RV) for the M2 dwarf GJ 176 based on spectra taken over 10yr from the High Resolution Spectrograph on the Hobby-Eberly Telescope. These data are supplemented with spectra from previous observations with the HIRES and HARPS spectrographs, and V- and R-band photometry taken over six years at the Dyer and Fairborn observatories. Previous studies of GJ 176 revealed a super-Earth exoplanet in an 8.8-day orbit. However, the velocities of this star are also known to be contaminated by activity, particularly at the 39-day stellar rotation period. We have examined the magnetic activity of GJ 176 using the sodium I D lines, which have been shown to be a sensitive activity tracer in cool stars. In addition to rotational modulation, we see evidence of a long-term trend in our Na I D index, which may be part of a long-period activity cycle. The sodium index is well correlated with our RVs, and we show that this activity trend drives a corresponding slope in RV. Interestingly, the rotation signal remains in phase in photometry, but not in the spectral activity indicators. We interpret this phenomenon as the result of one or more large spot complexes or active regions which dominate the photometric variability, while the spectral indices are driven by the overall magnetic activity across the stellar surface. In light of these results, we discuss the potential for correcting activity signals in the RVs of M dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/132
- Title:
- ~30yr of opt. spectroscopy & Vmag obs. of GW Ori
- Short Name:
- J/ApJ/851/132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spatially and spectrally resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of gas and dust orbiting the pre-main-sequence hierarchical triple-star system GW Ori. A forward modeling of the ^13^CO and C^18^O J=2-1 transitions permits a measurement of the total stellar mass in this system, 5.29+/-0.09M_{sun}_, and the circumtriple disk inclination, 137.6{deg}+/-2.0{deg}. Optical spectra spanning a 35yr period were used to derive new radial velocities and, coupled with a spectroscopic disentangling technique, revealed that the A and B components of GW Ori form a double-lined spectroscopic binary with a period of 241.50+/-0.05d; a tertiary companion orbits that inner pair with a period of 4218+/-50d. Combining the results from the ALMA data and the optical spectra with three epochs of astrometry in the literature, we constrain the individual stellar masses in the system (M_A_~2.7M_{sun}_, M_B_~1.7M_{sun}_, M_C_~0.9M_{sun}_) and find strong evidence that at least one of the stellar orbital planes (and likely both) is misaligned with the disk plane by as much as 45{deg}. A V-band light curve spanning 30yr reveals several new ~30-day eclipse events 0.1-0.7mag in depth and a 0.2mag sinusoidal oscillation that is clearly phased with the AB-C orbital period. Taken together, these features suggest that the A-B pair may be partially obscured by material in the inner disk as the pair approaches apoastron in the hierarchical orbit. Lastly, we conclude that stellar evolutionary models are consistent with our measurements of the masses and basic photospheric properties if the GW Ori system is ~1Myr old.
- ID:
- ivo://CDS.VizieR/J/ApJ/856/80
- Title:
- 6-yr optical monitoring of the FSRQ 3C 454.3
- Short Name:
- J/ApJ/856/80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our photometric monitoring of a flat spectrum radio quasar 3C 454.3 at Yunnan observatories from 2006 to 2011. We find that the optical color of 3C 454.3 shows an obvious redder-when-brighter trend, which reaches a saturation stage when the source is brighter than 15.15mag at V band. We perform a simulation with multiple values of disk luminosity and spectral index to reproduce the magnitude-color diagram. The results show that the contamination caused by the disk radiation alone is difficult to produce the observed color variability. The variability properties during the outburst in 2009 December are also compared with {gamma}-ray data derived from the Fermi {gamma}-ray space telescope. The flux variation of these two bands follows a linear relation with F_{gamma}_{propto}F_R_^1.14+/-0.07^, which provides observational evidence for the external Compton process in 3C 454.3. Meanwhile, this flux correlation indicates that electron injection is the main mechanism for the variability origin. We also explore the variation of the flux ratio F{gamma}/FR and the detailed structures in the light curves, and discuss some possible origins for the detailed variability behaviors.
- ID:
- ivo://CDS.VizieR/J/ApJS/232/7
- Title:
- 8yr R-band photopolarimetric data of blazar Mrk 421
- Short Name:
- J/ApJS/232/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of 8yr R-band photopolarimetric data of blazar Mrk 421 collected from 2008 February to 2016 May are presented, along with extensive multiwavelength observations covering radio to TeV {gamma}-rays around the flares observed in 2008 May, 2010 March, and 2013 April. The most important results are found in 2013, when the source displayed in the R band a very high brightness state of 11.29+/-0.03mag (93.60+/-1.53mJy) on April 10 and a polarization degree of 11.00%+/-0.44% on May 13. The analysis of the optical data shows that the polarization variability is due to the superposition of two polarized components that might be produced in two distinct emitting regions. An intranight photopolarimetric variability study carried out over seven nights after the 2013 April maximum found flux and polarization variations on the nights of April 14, 15, 16, and 19. In addition, the flux shows a minimum variability timescale of {Delta}t=2.34+/-0.12hr, and the polarization degree presents variations of~1%-2% on a timescale of {Delta}t~minutes. Also, a detailed analysis of the intranight data shows a coherence length of the large-scale magnetic field of l_B_~0.3pc, which is the same order of magnitude as the distance traveled by the relativistic shocks. This result suggests that there is a connection between the intranight polarimetric variations and spatial changes of the magnetic field. Analysis of the complete R-band data along with the historical optical light curve found for this object shows that Mrk 421 varies with a period of 16.26+/-1.78yr.
- ID:
- ivo://CDS.VizieR/J/ApJS/245/18
- Title:
- 9yr R-band photopolarimetric data of 3C 279
- Short Name:
- J/ApJS/245/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An exhaustive analysis of 9yr optical R-band photopolarimetric data of the flat-spectrum radio quasar 3C 279 from 2008 February 27 to 2017 May 25 is presented, along with multiwavelength observing campaigns performed during the flaring activity exhibited in 2009 February/March, 2011 June, 2014 March/April, 2015 June, and 2017 February. In the R band, this source showed the maximum brightness state of 13.68+/-0.11mag (1.36+/-0.20mJy) on 2017 March 2 and the lowest brightness state ever recorded of 18.20+/-0.87 mag (0.16+/-0.03mJy) on 2010 June 17. During the entire period of observations, the polarization degree varied between 0.48%+/-0.17% and 31.65%+/-0.77%, and the electric vector position angle (EVPA) exhibited large rotations between 82.98+/-0.92{deg} and 446.32+/-1.95{deg}. Optical polarization data show that this source has a stable polarized component that varied from~6% (before the 2009 flare) to~13% after the flare. The overall behavior of our polarized variability data supports the scenario of jet precessions as responsible for the observed large rotations of the EVPA. Discrete correlation function analysis shows that the lags between gamma-rays and X-rays compared to the optical R-band fluxes are {Delta}t~31 days and 1 day in 2009. Lags were also found among gamma-rays compared with X-rays and radio of {Delta}t~30 and 43 days in 2011, and among radio and optical R band of {Delta}t~10 days in 2014. A very intense flare in 2017 was observed in optical bands, with a dramatic variation in the polarization degree (from~6% to 20%) in 90 days without exhibiting flaring activity in other wavelengths.
- ID:
- ivo://CDS.VizieR/J/ApJ/837/30
- Title:
- 25yrs monitoring of stellar orbits in the GC
- Short Name:
- J/ApJ/837/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 25 years of data from uninterrupted monitoring of stellar orbits in the Galactic Center (GC), we present an update of the main results from this unique data set: a measurement of mass and distance to SgrA*. Our progress is not only due to the eight-year increase in time base, but also to the improved definition of the coordinate system. The star S2 continues to yield the best constraints on the mass of and distance to Sgr A*; the statistical errors of 0.13x10^6^M_{sun}_ and 0.12kpc have halved compared to the previous study. The S2 orbit fit is robust and does not need any prior information. Using coordinate system priors, the star S1 also yields tight constraints on mass and distance. For a combined orbit fit, we use 17 stars, which yields our current best estimates for mass and distance: M=4.28+/-0.10|_stat._+/-0.21|_sys_x10^6^M_{sun}_ and R_0_=8.32+/-0.07|_stat._+/-0.14|_sys_kpc. These numbers are in agreement with the recent determination of R_0_ from the statistical cluster parallax. The positions of the mass, of the near-infrared flares from Sgr A*, and of the radio source Sgr A* agree to within 1mas. In total, we have determined orbits for 40 stars so far, a sample which consists of 32 stars with randomly oriented orbits and a thermal eccentricity distribution, plus eight stars that we can explicitly show are members of the clockwise disk of young stars, and which have lower-eccentricity orbits.
- ID:
- ivo://CDS.VizieR/J/ApJ/836/124
- Title:
- 2yrs of eclipse data & precise RVs for LP661-13
- Short Name:
- J/ApJ/836/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of stellar eclipses in the LP 661-13 system. We present the discovery and characterization of this system, including high-resolution spectroscopic radial velocities and a photometric solution spanning two observing seasons. LP 661-13 is a low-mass binary system with an orbital period of 4.7043512_-0.0000010_^+0.0000013^d at a distance of 24.9+/-1.3pc. LP661-13A is a 0.30795+/-0.00084M_{sun}_ star, while LP661-13B is a 0.19400+/-0.00034M_{sun}_ star. The radius of each component is 0.3226+/-0.0033R_{sun}_ and 0.2174+/-0.0023R_{sun}_, respectively. We detect out-of-eclipse modulations at a period slightly shorter than the orbital period, implying that at least one of the components is not rotating synchronously. We find that each component is slightly inflated compared to stellar models, and that this cannot be reconciled through age or metallicity effects. As a nearby eclipsing binary system, where both components are near or below the full-convection limit, LP 661-13 will be a valuable test of models for the structure of cool dwarf stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/253/10
- Title:
- 12yrs of R-band photometry of the quasar 3C 454.3
- Short Name:
- J/ApJS/253/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we present 8523 pairs of R-band optical photometry observations for the quasar 3C 454.3 made during the period of 2006 October - 2018 February on the 70cm meniscus telescope at Abastumani Observatory, Georgia, to study its intraday variabilities (IDVs) and long-term variations, and we have come to the following results. (1) We detected 10 outbursts, a {Delta}R=3.825mag variation, and some IDVs. The IDV timescales are from 4.1 to 285 minutes, with the corresponding variability amplitude being A=2.9%-43.67%. The amplitude increases with IDV timescale. (2) The largest variation over a 1 day timescale is {Delta}R=1.38mag. (3) The IDV timescales suggest that the emission sizes are from 8.9x10^13^cm to 6.20x10^15^cm, and the magnetic field strengths are B=0.18-0.79G. (4) Period analysis results show three possible long-term periods, p=3.04+/-0.02yr, p=1.66+/-0.06yr, and p=1.20+/-0.03yr in the optical light curve. We adopted the accretion disk models and the lighthouse models to period p=3.04+/-0.02yr: in the accretion disk models, the binary black holes have masses M=1.17x10^9^M_{sun}_; in the lighthouse models, we used two boosted jet flux densities to fit the observational light curve. (5) WWZ analysis gives some short-period (high-frequency) signals associated with strong bursts (JD2454302 and JD2454521) with variable frequencies and lasting for the entire observation time span (11.3yr).
- ID:
- ivo://CDS.VizieR/J/ApJ/884/92
- Title:
- 7yrs of VRI obs. of S5 0716+714 and its flares
- Short Name:
- J/ApJ/884/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The typical blazar S5 0716+714 is very interesting due to its rapid and large-amplitude variability and high duty cycle of microvariability in the optical band. We analyze the observations in the I, R, and V bands obtained with the 1.0m telescope at Weihai observatory of Shandong University from 2011 to 2018. The model of synchrotron radiation from turbulent cells in a jet has been proposed as a mechanism for explaining microvariability seen in blazar light curves. Parameters such as the sizes of turbulent cells, the enhanced particle densities, and the location of the turbulent cells in the jet can be studied using this model. The model predicts a time lag between variations, as observed in different frequency bands. An automatic model fitting method for microvariability is developed, and the fitting results of our multi-frequency microvariability observations support the model. The results show that both the amplitude and duration of flares decomposed from the microvariability light curves conform to the log-normal distribution. The turbulent cell size is within the range of about 5-55au, and the time lags of the microvariability flares between the I-R and R-V bands should be several minutes. The time lags obtained from the turbulence model are consistent with the fitting statistical results, and the time lags of flares are correlated with the time lags of the whole light curve.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A116
- Title:
- YSO candidate catalog from ANN
- Short Name:
- J/A+A/647/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observed young stellar objects (YSOs) are used to study star formation and characterize star-forming regions. For this purpose, YSO candidate catalogs are compiled from various surveys, especially in the infrared (IR), and simple selection schemes in color-magnitude diagrams (CMDs) are often used to identify and classify YSOs. We propose a methodology for YSO classification through machine learning (ML) using Spitzer IR data. We detail our approach in order to ensure reproducibility and provide an in-depth example on how to efficiently apply ML to an astrophysical classification. We used feed forward artificial neural networks (ANNs) that use the four IRAC bands (3.6, 4.5, 5.8, and 8 micron) and the 24 micron MIPS band from Spitzer to classify point source objects into CI and CII YSO candidates or as contaminants. We focused on nearby (~1kpc) star-forming regions including Orion and NGC 2264, and assessed the generalization capacity of our network from one region to another. We found that ANNs can be efficiently applied to YSO classification with a contained number of neurons (~25). Knowledge gathered on one star-forming region has shown to be partly efficient for prediction in new regions. The best generalization capacity was achieved using a combination of several star-forming regions to train the network. Carefully rebalancing the training proportions was necessary to achieve good results. We observed that the predicted YSOs are mainly contaminated by under-constrained rare subclasses like Shocks and polycyclic aromatic hydrocarbons (PAHs), or by the vastly dominant other kinds of stars (mostly on the main sequence). We achieved above 90% and 97% recovery rate for CI and CII YSOs, respectively, with a precision above 80% and 90% for our most general results. We took advantage of the great flexibility of ANNs to define, for each object, an effective membership probability to each output class. Using a threshold in this probability was found to efficiently improve the classification results at a reasonable cost of object exclusion. With this additional selection, we reached 90% and 97% precision on CI and CII YSOs, respectively, for more than half of them. Our catalog of YSO candidates in Orion (365 CI, 2381 CII) and NGC 2264 (101 CI, 469 CII) predicted by our final ANN, along with the class membership probability for each object, is publicly available at the CDS. Compared to usual CMD selection schemes, ANNs provide a possibility to quantitatively study the properties and quality of the classification. Although some further improvement may be achieved by using more powerful ML methods, we established that the result quality depends mostly on the training set construction. Improvements in YSO identification with IR surveys using ML would require larger and more reliable training catalogs, either by taking advantage of current and future surveys from various facilities like VLA, ALMA, or Chandra, or by synthesizing such catalogs from simulations.
- ID:
- ivo://CDS.VizieR/J/ApJS/240/26
- Title:
- YSO candidates in Canis Major OB1 association
- Short Name:
- J/ApJS/240/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a very young star-forming region in the outer Galaxy that is the most concentrated source of outflows in the Spitzer Space Telescope GLIMPSE360 survey. This region, dubbed CMa-l224, is located in the Canis Major OB1 association. CMa-l224 is relatively faint in the mid-infrared, but it shines brightly at the far-infrared wavelengths as revealed by the Herschel Space Observatory data from the Hi-GAL survey. Using the 3.6 and 4.5{mu}m data from the Spitzer/GLIMPSE360 survey, combined with the JHKs Two Micron All Sky Survey (2MASS) and the 70-500{mu}m Herschel/Hi-GAL data, we develop young stellar object (YSO) selection criteria based on color-color cuts and fitting of the YSO candidates' spectral energy distributions with YSO 2D radiative transfer models. We identify 293 YSO candidates and estimate physical parameters for 210 sources well fit with YSO models. We select an additional 47 sources with GLIMPSE360-only photometry as "possible YSO candidates." The vast majority of these sources are associated with high H2 column density regions and are good targets for follow-up studies. The distribution of YSO candidates at different evolutionary stages with respect to Herschel filaments supports the idea that stars are formed in the filaments and become more dispersed with time. Both the supernova-induced and spontaneous star formation scenarios are plausible in the environmental context of CMa-l224. However, our results indicate that a spontaneous gravitational collapse of filaments is a more likely scenario. The methods developed for CMa-l224 can be used for larger regions in the Galactic plane where the same set of photometry is available.
- ID:
- ivo://CDS.VizieR/J/ApJ/770/1
- Title:
- YSO candidates in G38.9-0.4 region
- Short Name:
- J/ApJ/770/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the star formation (SF) region G38.9-0.4 using publicly available multiwavelength Galactic plane surveys from ground- and space-based observatories. This region is composed of four bright mid-IR bubbles and numerous infrared dark clouds. Two bubbles, N 74 and N 75, each host a star cluster anchored by a single O9.5V star. We identified 162 young stellar objects (YSOs) and classify 54 as stage I, 7 as stage II, 6 as stage III, and 32 as ambiguous. We do not detect the classical signposts of triggered SF, i.e., star-forming pillars or YSOs embedded within bubble rims. We conclude that feedback-triggered SF has not occurred in G38.9-0.4. The YSOs are preferentially coincident with infrared dark clouds. This leads to a strong correlation between areal YSO mass surface density and gas mass surface density with a power law slope near 1.3, which closely matches the Schmidt-Kennicutt Law. The correlation is similar inside and outside the bubbles and may mean that the SF efficiency is neither enhanced nor suppressed in regions potentially influenced by stellar feedback. This suggests that gas density, regardless of how it is collected, is a more important driver of SF than stellar feedback. Larger studies should be able to quantify the fraction of all SF that is feedback-triggered by determining the fraction SF, feedback-compressed gas surrounding H II regions relative to that already present in molecular clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/599/A37
- Title:
- YSO candidates in IRAS 20319+3958
- Short Name:
- J/A+A/599/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Globules and pillars, impressively revealed by the Spitzer and Herschel satellites, for example, are pervasive features found in regions of massive star formation. Studying their embedded stellar populations can provide an excellent laboratory to test theories of triggered star formation and the features that it may imprint on the stellar aggregates resulting from it. We studied the globule IRAS 20319+3958 in Cygnus X by means of visible and near-infrared imaging and spectroscopy, complemented with mid-infrared Spitzer/IRAC imaging, in order to obtain a census of its stellar content and the nature of its embedded sources. Our observations show that the globule contains an embedded aggregate of about 30 very young (<~1Myr) stellar objects, for which we estimate a total mass of ~90M_{sun}_. The most massive members are three systems containing early B-type stars. Two of them most likely produced very compact HII regions, one of them being still highly embedded and coinciding with a peak seen in emission lines characterising the photon dominated region (PDR). Two of these three systems are resolved binaries, and one of those contains a visible Herbig Be star. An approximate derivation of the mass function of the members of the aggregate gives hints of a slope at high masses shallower than the classical Salpeter slope, and a peak of the mass distribution at a mass higher than that at which the widely adopted log-normal initial mass function peaks. The emission distribution of H_2_ and Brackett gamma, tracing the PDR and the ionised gas phase, respectively, suggests that molecular gas is distributed as a shell around the embedded aggregate, filled with centrally-condensed ionised gas. Both, the morphology and the low excitation of the HII region, indicate that the sources of ionisation are the B stars of the embedded aggregate, rather than the external UV field caused by the O stars of Cygnus OB2. The youth of the embedded cluster, combined with the isolation of the globule, suggests that star formation in the globule was triggered by the passage of the ionisation front.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/L285
- Title:
- YSO candidates in M17 SWex
- Short Name:
- J/ApJ/714/L285
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Through analysis of archival images and photometry from the Spitzer GLIMPSE and MIPSGAL surveys combined with Two Micron All Sky Survey and MSX data, we have identified 488 candidate young stellar objects (YSOs) in the giant molecular cloud M17 SWex, which extends ~50pc southwest from the prominent Galactic HII region M17. Our sample includes >200 YSOs with masses >3M_{sun}_ that will become B-type stars on the main sequence. Extrapolating over the stellar initial mass function (IMF), we find that M17 SWex contains >1.3x10^4^ young stars, representing a proto-OB association. The YSO mass function is significantly steeper than the Salpeter IMF, and early O stars are conspicuously absent from M17 SWex. Assuming M17 SWex will form an OB association with a Salpeter IMF, these results reveal the combined effects of (1) more rapid circumstellar disk evolution in more massive YSOs and (2) delayed onset of massive star formation.
3677. YSO candidates in S169
- ID:
- ivo://CDS.VizieR/J/A+A/646/A103
- Title:
- YSO candidates in S169
- Short Name:
- J/A+A/646/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the aim of studying the physical properties of Galactic IR bubbles and to explore their impact in massive star formation, we present a study of the IR bubble S169, associated with the massive star forming region IRAS 12326-6245. We used CO (2-1),^13^CO (2-1), C^18^O (2-1), HCN (3-2), and HCO^+^ (3-2) line data obtained with the APEX telescope using the on-the-fly full sampling technique to study the properties of the molecular gas in the nebula and the IRAS source. To analyze the properties and distribution of the dust, we made use of images obtained from the IRAC-GLIMPSE, Herschel, and ATLASGAL archives. The properties of the ionized gas in the nebula were studied using radio continuum and H{alpha} images obtained from the SUMSS survey and SuperCOSMOS database, respectively. In our search for stellar and protostellar objects in the region, we used point source calalogs obtained from the MSX, WISE, GLIMPSE, 2MASS, AAVSO, ASCC-2.5V3, and GAIA databases. The new APEX observations allowed us to identify three molecular components, each one associated with different regions of the nebula, namely: at -39km/s (component A), -25km/s (component B), and -17km/s (component C). Component A is shown to be the most dense and clumpy. Six molecular condensations (MC1 to MC6) were identified in this component, with MC3 (the densest and more massive one) being the molecular counterpart of IRAS 12326-6245. For this source, we estimated an H_2_ column density up to 8x10^23^cm^-2^. An LTE analysis of the high density tracer lines HCO^+^ (3-2) and HCN (3-2) on this source, assuming 50 and 150K, respectively, indicates column densities of N(HCO^+^)=(5.2+/-0.1)x10^13^cm^-2^ and N(HCN)=(1.9+/-0.5)x10^14^cm^-2^. To explain the morphology and velocity of components A, B, and C, we propose a simple model consisting of a partially complete semisphere-like structure expanding at ~12km/s. The introduction of this model has led to a discussion about the distance to both S169 and IRAS 12326-6245, which was estimated to be ~2kpc. Several candidate YSOs were identified, projected mostly onto the molecular condensations MC3, MC4, and MC5, which indicates that the star-formation process is very active at the borders of the nebula. A comparison between observable and modeled parameters was not enough to discern whether the collect-and-collapse mechanism is acting at the edge of S169. However, other processes such as radiative-driven implosion or even a combination of both mechanisms, namely, collect-and-collapse and radiative-driven implosion, could be acting simultaneously in the region.
- ID:
- ivo://CDS.VizieR/J/ApJ/830/57
- Title:
- YSO candidates in the dust bubble N10 with WISE
- Short Name:
- J/ApJ/830/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied the environment of the dust bubble N10 in molecular emission. Infrared bubbles, first detected by the GLIMPSE survey at 8.0{mu}m, are ideal regions to investigate the effect of the expansion of the HII region on its surroundings and the eventual triggering of star formation at its borders. In this work, we present a multi-wavelength study of N10. This bubble is especially interesting because infrared studies of the young stellar content suggest a scenario of ongoing star formation, possibly triggered on the edge of the HII region. We carried out observations of ^12^CO(1-0) and ^13^CO(1-0) emission at PMO 13.7m toward N10. We also analyzed the IR and sub-millimeter emission on this region and compare those different tracers to obtain a detailed view of the interaction between the expanding HII region and the molecular gas. We also estimated the parameters of the denser cold dust condensation and the ionized gas inside the shell. Bright CO emission was detected and two molecular clumps were identified from which we have derived physical parameters. We also estimate the parameters for the densest cold dust condensation and for the ionized gas inside the shell. The comparison between the dynamical age of this region and the fragmentation timescale favors the "Radiation-Driven Implosion" mechanism of star formation. N10 is a case of particular interest with gas structures in a narrow frontier between the HII region and surrounding molecular material, and with a range of ages of YSOs situated in the region, indicating triggered star formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/797/40
- Title:
- YSO candidates in the IR dust bubble N6
- Short Name:
- J/ApJ/797/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a multiwavelength study of the infrared dust bubble N6 to extensively investigate the molecular environs and star-forming activities therein. 99 young stellar objects (YSOs) have been identified based on their infrared colors. A group of YSOs reside inside the ring, indicating active star formation in N6. Although no confirmative features of triggered star formation are detected, the bubble and the enclosed HII region have profoundly reconstructed the natal cloud and altered the dynamics therein.
- ID:
- ivo://CDS.VizieR/J/ApJ/785/162
- Title:
- YSO candidates in the Magellanic Bridge
- Short Name:
- J/ApJ/785/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Magellanic Bridge is the nearest low-metallicity, tidally stripped environment, offering a unique high-resolution view of physical conditions in merging and forming galaxies. In this paper, we present an analysis of candidate massive young stellar objects (YSOs), i.e., in situ, current massive star formation (MSF) in the Bridge using Spitzer mid-IR and complementary optical and near-IR photometry. While we definitely find YSOs in the Bridge, the most massive are ~10 M_{sun}_<<45 M_{sun}_ found in the LMC. The intensity of MSF in the Bridge also appears to be decreasing, as the most massive YSOs are less massive than those formed in the past. To investigate environmental effects on MSF, we have compared properties of massive YSOs in the Bridge to those in the LMC. First, YSOs in the Bridge are apparently less embedded than in the LMC: 81% of Bridge YSOs show optical counterparts, compared to only 56% of LMC sources with the same range of mass, circumstellar dust mass, and line-of-sight extinction. Circumstellar envelopes are evidently more porous or clumpy in the Bridge's low-metallicity environment. Second, we have used whole samples of YSOs in the LMC and the Bridge to estimate the probability of finding YSOs at a given H I column density, N(H I). We found that the LMC has ~3xhigher probability than the Bridge for N(H I)>12x10^20^/cm^2^, but the trend reverses at lower N(H I). Investigating whether this lower efficiency relative to H I is due to less efficient molecular cloud formation or to less efficient cloud collapse, or to both, will require sensitive molecular gas observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/813/25
- Title:
- YSO candidates in W49 observed with Spitzer
- Short Name:
- J/ApJ/813/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the initial results of our investigation of the star-forming complex W49, one of the youngest and most luminous massive star-forming regions in our Galaxy. We used Spitzer/Infrared Array Camera (IRAC) data to investigate massive star formation with the primary objective of locating a representative set of protostars and the clusters of young stars that are forming around them. We present our source catalog with the mosaics from the IRAC data. In this study we used a combination of IRAC, MIPS, Two Micron All Sky Survey, and UKIRT Deep Infrared Sky Survey (UKIDSS) data to identify and classify the young stellar objects (YSOs). We identified 232 Class 0/I YSOs, 907 Class II YSOs, and 74 transition disk candidate objects using color-color and color-magnitude diagrams. In addition, to understand the evolution of star formation in W49, we analyzed the distribution of YSOs in the region to identify clusters using a minimal spanning tree method. The fraction of YSOs that belong to clusters with >=7 members is found to be 52% for a cutoff distance of 96", and the ratio of Class II/I objects is 2.1. We compared the W49 region to the G305 and G333 star-forming regions and concluded that W49 has the richest population, with seven subclusters of YSOs.
- ID:
- ivo://CDS.VizieR/J/ApJ/818/95
- Title:
- YSO candidates within 5' from the IR bubble N4
- Short Name:
- J/ApJ/818/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The physical mechanisms that induce the transformation of a certain mass of gas in new stars are far from being well understood. Infrared bubbles associated with H II regions have been considered to be good samples for investigating triggered star formation. In this paper we report on the investigation of the dust properties of the infrared bubble N4 around the H II region G11.898+0.747, analyzing its interaction with its surroundings and star formation histories therein, with the aim of determining the possibility of star formation triggered by the expansion of the bubble. Using Herschel PACS and SPIRE images with a wide wavelength coverage, we reveal the dust properties over the entire bubble. Meanwhile, we are able to identify six dust clumps surrounding the bubble, with a mean size of 0.50pc, temperature of about 22K, mean column density of 1.7x10^22^/cm2, mean volume density of about 4.4x10^4^/cm3, and a mean mass of 320M_{sun}_. In addition, from PAH emission seen at 8 {mu}m, free-free emission detected at 20cm, and a probability density function in special regions, we could identify clear signatures of the influence of the HII region on the surroundings. There are hints of star formation, though further investigation is required to demonstrate that N4 is the triggering source.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/8
- Title:
- YSO jets from UWISH2. IV. Cygnus-X outflows
- Short Name:
- J/ApJS/234/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed an unbiased search for outflows from young stars in Cygnus-X using 42deg^2^ of data from the UKIRT Widefield Infrared Survey for H_2_ (UWISH2 Survey), to identify shock-excited near-IR H_2_ emission in the 1-0 S(1) 2.122{mu}m line. We uncovered 572 outflows, of which 465 are new discoveries, increasing the number of known objects by more than 430%. This large and unbiased sample allows us to statistically determine the typical properties of outflows from young stars. We found 261 bipolar outflows, and 16% of these are parsec scale. The typical bipolar outflow is 0.45pc in length and has gaps of 0.025-0.1pc between large knots. The median luminosity in the 1-0 S(1) line is 10^-3^L_{sun}_. The bipolar flows are typically asymmetrical, with the two lobes misaligned by 5{deg}, one lobe 30% shorter than the other, and one lobe twice as bright as the other. Of the remaining outflows, 152 are single- sided and 159 are groups of extended, shock-excited H2 emission without identifiable driving sources. Half of all driving sources have sufficient WISE data to determine their evolutionary status as either protostars (80%) or classical T Tauri stars (20%). One-fifth of the driving sources are variable by more than 0.5mag in the K-band continuum over several years. Several of the newly identified outflows provide excellent targets for follow-up studies. We particularly encourage the study of the outflows and young stars identified in a bright-rimmed cloud near IRAS 20294+4255, which seems to represent a textbook example of triggered star formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/53
- Title:
- YSO/MS star models in the central molecular zone
- Short Name:
- J/ApJ/799/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In contrast to most other galaxies, star formation rates in the Milky Way can be estimated directly from young stellar objects (YSOs). In the central molecular zone the star formation rate calculated from the number of YSOs with 24{mu}m emission is up to an order of magnitude higher than the value estimated from methods based on diffuse emission (such as free-free emission). Whether this effect is real or whether it indicates problems with either or both star formation rate measures is not currently known. In this paper, we investigate whether estimates based on YSOs could be heavily contaminated by more evolved objects such as main-sequence stars. We present radiative transfer models of YSOs and of main-sequence stars in a constant ambient medium which show that the main-sequence objects can indeed mimic YSOs at 24{mu}m. However, we show that in some cases the main-sequence models can be marginally resolved at 24{mu}m, whereas the YSO models are always unresolved. Based on the fraction of resolved MIPS 24{mu}m sources in the sample of YSOs previously used to compute the star formation rate, we estimate the fraction of misclassified "YSOs" to be at least 63%, which suggests that the star formation rate previously determined from YSOs is likely to be at least a factor of three too high.
3685. YSOs around Cepheus B
- ID:
- ivo://CDS.VizieR/J/ApJ/699/1454
- Title:
- YSOs around Cepheus B
- Short Name:
- J/ApJ/699/1454
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Cepheus B (Cep B) molecular cloud and a portion of the nearby Cep OB3b OB association, one of the most active regions of star formation within 1kpc, have been observed with the Infrared Array Camera detector on board the Spitzer Space Telescope. The goals are to study protoplanetary disk evolution and processes of sequential triggered star formation in the region. Out of ~400 pre-main-sequence (PMS) stars selected with an earlier Chandra X-ray Observatory observation, ~95% are identified with mid-infrared sources and most of these are classified as diskless or disk-bearing stars. The discovery of the additional >200 IR-excess low-mass members gives a combined Chandra+Spitzer PMS sample that is almost complete down to 0.5M_{sun}_ outside of the cloud, and somewhat above 1M_{sun}_ in the cloud.
- ID:
- ivo://CDS.VizieR/J/ApJS/194/43
- Title:
- YSOs candidates and knots in CrA cloud
- Short Name:
- J/ApJS/194/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer Space Telescope IRAC and MIPS observations of a 0.85deg^2^ field including the Corona Australis (CrA) star-forming region. At a distance of 130pc, CrA is one of the closest regions known to be actively forming stars, particularly within its embedded association, the Coronet. Using the Spitzer data, we identify 51 young stellar objects (YSOs) in CrA which include sources in the well-studied Coronet cluster as well as sources distributed throughout the molecular cloud. Twelve of the YSOs discussed are new candidates, one of which is located in the Coronet. Known YSOs retrieved from the literature are also added to the list, and a total of 116 candidate YSOs in CrA are compiled. A clustering analysis was also performed, finding that the main cluster core, consisting of 68 members, is elongated (having an aspect ratio of 2.36), with a circular radius of 0.59pc and mean surface density of 150pc^-2^. In addition, we analyze outflows and jets in CrA by means of new CO and H2 data. We present 1.3mm interferometric continuum observations made with the Submillimeter Array (SMA) covering R CrA, IRS 5, IRS 7, and IRAS 18595-3712 (IRAS 32).
- ID:
- ivo://CDS.VizieR/J/PASP/132/J4401
- Title:
- YSOs detection with W filter
- Short Name:
- J/PASP/132/J4401
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the design and implementation of a medium-band near-IR filter tailored for detecting low-mass stars and brown dwarfs from the summit of Maunakea. The W-band filter is centered at 1.45{mu}m with a bandpass width of 6%, designed to measure the depth of the H_2_O water absorption prominent in objects with spectral types of M6 and later. When combined with standard J and H photometry, the W-band filter is designed to determine spectral types to ~=1.4 subtypes for late-M and L dwarfs, largely independent of surface gravity and reddening. This filter's primary application is completing the census of young substellar objects in star-forming regions, using W-band selection to greatly reduce contamination by reddened background stars that impede broad-band imaging surveys. We deployed the filter on the UH 88 inch telescope to survey ~3 degree^2^ of the NGC 1333, IC 348, and {rho} Ophiuchus star-forming regions. Our spectroscopic followup of W-band selected candidates resulted in the confirmation of 48 ultracool dwarfs with a success rate of 89%, demonstrating the efficacy of this new filter and selection method.
- ID:
- ivo://CDS.VizieR/J/ApJ/733/L2
- Title:
- YSOs from WISE in Western Circinus cloud
- Short Name:
- J/ApJ/733/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Wide-field Infrared Survey Explorer has uncovered a population of young stellar objects (YSOs) in the Western Circinus molecular cloud. Images show the YSOs to be clustered into two main groups that are coincident with dark filamentary structure in the nebulosity. Analysis of photometry shows numerous Class I and II objects. The locations of several of these objects are found to correspond to known dense cores and CO outflows. Class I objects tend to be concentrated in dense aggregates, and Class II objects more evenly distributed throughout the region.
3689. YSOs in BRC 5, 7 and 39
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/1614
- Title:
- YSOs in BRC 5, 7 and 39
- Short Name:
- J/MNRAS/443/1614
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Bright-rimmed clouds (BRCs), illuminated and shaped by nearby OB stars, are potential sites of recent/ongoing star formation. Here we present an optical and infrared photometric study of three BRCs: BRC 5, BRC 7 and BRC 39 to obtain a census of the young stellar population, thereby inferring the star formation scenario, in these regions. In each BRC, the Class I sources are found to be located mostly near the bright rim or inside the cloud, whereas the Class II sources are preferentially outside, with younger sources closer to the rim. This provides strong support to sequential star formation triggered by radiation-driven implosion due to the ultraviolet radiation. Moreover, each BRC contains a small group of young stars being revealed at its head, as the next-generation stars. In particular, the young stars at the heads of BRC 5 and BRC 7 are found to be intermediate-/high-mass stars, which, under proper conditions, may themselves trigger further star birth, thereby propagating star formation out to long distances.
- ID:
- ivo://CDS.VizieR/J/A+A/519/A34
- Title:
- YSOs in DROXO (Deep rho Oph XMM obs.)
- Short Name:
- J/A+A/519/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- X-rays from very young stars are powerful probes to investigate the mechanisms at work in the very first stages of the star formation and the origin of X-ray emission in very young stars. We present results from a 500ks long observation of the rho Ophiuchi cloud with a XMM-Newton large program named DROXO, aiming at studying the X-ray emission of deeply embedded young stellar objects (YSOs).
- ID:
- ivo://CDS.VizieR/J/ApJS/207/5
- Title:
- YSOs in LDN 1641 with Hectochelle spectra
- Short Name:
- J/ApJS/207/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the young stellar objects (YSOs) in the Lynds 1641 (L1641) cloud using multi-wavelength data including Spitzer, WISE, the Two Micron All Sky Survey, and XMM covering ~1390 YSOs across a range of evolutionary stages. In addition, we targeted a sub-sample of YSOs for optical spectroscopy with the MMT/Hectospec and the MMT/Hectochelle. We use these data, along with archival photometric data, to derive spectral types, extinction values, masses, ages, and accretion rates. We obtain a disk fraction of ~50% in L1641. The disk frequency is almost constant as a function of stellar mass with a slight peak at log (M_*_/M_{sun}_){approx}-0.25. The analysis of multi-epoch spectroscopic data indicates that the accretion variability of YSOs cannot explain the two orders of magnitude of scatter for YSOs with similar masses. Forty-six new transition disk (TD) objects are confirmed in this work, and we find that the fraction of accreting TDs is lower than for optically thick disks (40%-45% versus 77%-79%, respectively). We confirm our previous result that the accreting TDs have a median accretion rate similar to normal optically thick disks. We confirm that two star formation modes (isolated versus clustered) exist in L1641. We find that the diskless YSOs are statistically older than the YSOs with optically thick disks and the TD objects have a median age that is intermediate between those of the other two populations. We tentatively study the star formation history in L1641 based on the age distribution and find that star formation started to be active 2-3 Myr ago.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A66
- Title:
- YSOs in 9 LMC star forming regions
- Short Name:
- J/A+A/542/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce a new set of selection criteria for the identification of infrared bright young stellar object (YSO) candidates and apply them to nine HII regions in the Large Magellanic Cloud (LMC), focusing particularly on lower mass candidates missed by most surveys. Data are from the Spitzer Space Telescope legacy program SAGE (Surveying the Agents of Galaxy Evolution; Meixner et al. 2006, Cat. J/AJ/132/2268, see also II/305), combined with optical photometry from the Magellanic Clouds Photometric Survey (MCPS; Zaritsky et al. 1997AJ....114.1002Z) and near-infrared photometry from the InfraRed Survey Facility (IRSF; Kato et al. 2007, Cat. II/288). We choose regions of diverse physical size, star formation rates (SFRs), and ages. We also cover a wide range of locations and surrounding environments in the LMC. These active star-forming regions are LHA 120-N 11, N 44, N 51, N 105, N 113, N 120, N 144, N 160, and N 206. Some have been well-studied (e.g., N11, N44, N160) in the past, while others (e.g., N51, N144) have received little attention. We identify 1045 YSO candidates, including 918 never before identified and 127 matching previous candidate lists. We characterize the evolutionary stage and physical properties of each candidate using the spectral energy distribution (SED) fitter of Robitaille et al. (2007ApJS..169..328R) and estimate mass functions and SFRs for each region.
3693. YSOs in L1630N and L1641
- ID:
- ivo://CDS.VizieR/J/A+A/504/461
- Title:
- YSOs in L1630N and L1641
- Short Name:
- J/A+A/504/461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Knowledge of the evolution of circumstellar accretion disks is pivotal to our understanding of star and planet formation; and yet despite intensive theoretical and observational studies, the disk dissipation process is not well understood. Infrared observations of large numbers of young stars, as performed by the Spitzer Space Telescope, may advance our knowledge of this inherently complex process. While infrared data reveal the evolutionary status of the disk, they hold little information on the properties of the central star and the accretion characteristics. Existing 2MASS and Spitzer archive data of the Lynds 1630N and 1641 clouds in the Orion GMC provide disk properties of a large number of young stars. We wish to complement these data with optical data that provide the physical stellar parameters and accretion characteristics.
3694. YSOs in N63 and N180
- ID:
- ivo://CDS.VizieR/J/ApJ/678/200
- Title:
- YSOs in N63 and N180
- Short Name:
- J/ApJ/678/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used Spitzer infrared observations to find the young stars of two HII regions in the Large Magellanic Cloud, N63 and N180. The young stellar object (YSO) candidates were identified in each nebula by means of color-color, color-magnitude diagrams, and the shapes of their spectral energy distributions (SEDs). The most luminous YSOs are found near the ionization fronts within strong 8um emission clumps. Most YSOs, less luminous, are seen in projection inside the HII regions. HST images show several Class I stars that have emerged along the borders of the HII regions; other YSOs are embedded in cometary clouds. The most luminous YSO of N63 is connected to a string of pointlike sources. Its SED can be modeled by a central source of stellar mass M_*_ between 7 and 11M_{sun}_, with a circumstellar disk of outer radius R_d_ of ~55AU, and an envelope of moderate accretion rate, M_env_ of ~2x10^-5^M_{sun}_/yr. N180 is experiencing a phase of star formation more intense than N63, attested by the properties of its most luminous YSO: M_*_ of 25M_{sun}_, R_d_ of ~200AU, and M_env_ of ~1.5x10^-3^M_{sun}_/yr. The modes of triggered star formation in N63 and N180 appear similar to those seen in Galactic HII regions.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/2325
- Title:
- YSOs in star-forming region associated to V582 Aur
- Short Name:
- J/MNRAS/468/2325
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied the environment of the FU Ori type star V582 Aur. Our aim is to explore the star-forming region associated with this young eruptive star. Using slitless spectroscopy, we searched for H{alpha} emission stars within a field of 11.5 arcmin x 11.5 arcmin, centred on V582 Aur. Based on UKIDSS and Spitzer Space Telescope data, we further selected infrared-excess young stellar object candidates. In all, we identified 68 candidate low-mass young stars, 16 of which exhibited H{alpha} emission in the slitless spectroscopic images. The colour-magnitude diagram of the selected objects, based on the IPHAS data, suggests that they are low-mass pre-main-sequence stars associated with the Aur OB 1 association, located at a distance of 1.3kpc from Sun. The bright-rimmed globules in the local environment of V582 Aur probably belong to the dark cloud LDN 1516. Our results suggest that star formation in these globules might have been triggered by the radiation field of a few hot members of Aur OB 1. The bolometric luminosity of V582 Aur, based on archival photometric data and on the adopted distance, is 150-320L_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/759/48
- Title:
- YSOs in the Galactic HII region Sh2-297
- Short Name:
- J/ApJ/759/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiwavelength study of the Galactic H II region Sh2-297, located in the Canis Major OB1 complex. Optical spectroscopic observations are used to constrain the spectral type of ionizing star HD 53623 as B0V. The classical nature of this H II region is affirmed by the low values of electron density and emission measure, which are calculated to be 756/cm3 and 9.15x10^5^cm^-6^pc using the radio continuum observations at 610 and 1280MHz, and Very Large Array archival data at 1420MHz. To understand local star formation, we identified the young stellar object (YSO) candidates in a region of area ~7.5'x7.5' centered on Sh2-297 using grism slitless spectroscopy (to identify the H{alpha} emission line stars), and near infrared (NIR) observations. NIR YSO candidates are further classified into various evolutionary stages using color-color and color-magnitude (CM) diagrams, giving 50 red sources (H-K>0.6) and 26 Class II-like sources. The mass and age range of the YSOs are estimated to be ~0.1-2M_{sun}_ and 0.5-2Myr using optical (V/V-I) and NIR (J/J-H) CM diagrams. The mean age of the YSOs is found to be ~1Myr, which is of the order of dynamical age of 1.07Myr of the H II region. Using the estimated range of visual extinction (1.1-25mag) from literature and NIR data for the region, spectral energy distribution models have been implemented for selected YSOs which show masses and ages to be consistent with estimated values. The spatial distribution of YSOs shows an evolutionary sequence, suggesting triggered star formation in the region. The star formation seems to have propagated from the ionizing star toward the cold dark cloud LDN1657A located west of Sh2-297.
- ID:
- ivo://CDS.VizieR/J/A+A/362/199
- Title:
- YSOs in the l=+45 ISOGAL field
- Short Name:
- J/A+A/362/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 7 and 15{mu}m observations of the Galaxy obtained by the ISOGAL program offer an unique possibility to investigate and separate the different populations of stars in the Galactic Plane, in particular to study the population of low flux density YSOs which could not be detected with IRAS.
- ID:
- ivo://CDS.VizieR/J/ApJ/721/357
- Title:
- YSOs in the LMC star-forming region N206
- Short Name:
- J/ApJ/721/357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present analysis of the energetic star-forming region Henize 206 (N206) located near the southern edge of the Large Magellanic Cloud (LMC) based on photometric data from the Spitzer Surveying the Agents of Galaxy Evolution (SAGE-LMC; IRAC 3.6, 4.5, 5.8, 8.0um and MIPS 24um), Infrared Survey Facility near-infrared survey (J, H, Ks), and the Magellanic Clouds Photometric Survey (MCPS UBVI) covering a wavelength range of 0.36-24um. Young stellar object (YSO) candidates are identified based upon their location in infrared color-magnitude space and classified by the shapes of their spectral energy distributions in comparison with a pre-computed grid of YSO models. We identify 116 YSO candidates: 102 are well characterized by the YSO models, predominately Stage I, and 14 may be multiple sources or young sources with transition disks. Careful examination of the individual sources and their surrounding environment allows us to identify a factor of ~14.5 more YSO candidates than have already been identified. The total mass of these well-fit YSO candidates is ~520M_{sun}_. We calculate a current star formation rate of 0.27x10^-1^M_{sun}_/yr/kpc^2^. The distribution of YSO candidates appears to follow shells of neutral material in the interstellar medium.
- ID:
- ivo://CDS.VizieR/J/ApJ/839/108
- Title:
- YSOs in the star-forming regions W51 & W43
- Short Name:
- J/ApJ/839/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our investigation of the star-forming complexes W51 and W43, two of the brightest in the first Galactic quadrant. In order to determine the young stellar object (YSO) populations in W51 and W43 we used color-magnitude relations based on Spitzer mid-infrared and 2MASS/UKIDSS near- infrared data. We identified 302 Class I YSOs and 1178 Class II/transition disk candidates in W51, and 917 Class I YSOs and 5187 Class II/transition disk candidates in W43. We also identified tens of groups of YSOs in both regions using the Minimal Spanning Tree (MST) method. We found similar cluster densities in both regions, even though Spitzer was not able to probe the densest part of W43. By using the Class II/I ratios, we traced the relative ages within the regions and, based on the morphology of the clusters, we argue that several sites of star formation are independent of one another in terms of their ages and physical conditions. We used spectral energy distribution- fitting to identify the massive YSO (MYSO) candidates since they play a vital role in the star formation process, and then examined them to see if they are related to any massive star formation tracers such as UCH II regions, masers, or dense fragments. We identified 17 MYSO candidates in W51, and 14 in W43, respectively, and found that groups of YSOs hosting MYSO candidates are positionally associated with H II regions in W51, though we do not see any MYSO candidates associated with previously identified massive dense fragments in W43.
- ID:
- ivo://CDS.VizieR/J/ApJ/712/797
- Title:
- YSOs in Vul OB1 association
- Short Name:
- J/ApJ/712/797
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Vulpecula OB association, Vul OB1, is a region of active star formation located in the Galactic plane at 2.3kpc from the Sun. Previous studies suggest that sequential star formation is propagating along this 100pc long molecular complex. In this paper, we use Spitzer MIPSGAL and GLIMPSE data to reconstruct the star formation history of Vul OB1, and search for signatures of past triggering events. We make a census of young stellar objects (YSOs) in Vul OB1 based on IR color and magnitude criteria, and we rely on the properties and nature of these YSOs to trace recent episodes of massive star formation. We find 856 YSO candidates, and show that the evolutionary stage of the YSO population in Vul OB1 is rather homogeneous -ruling out the scenario of propagating star formation. We estimate the current star formation efficiency to be ~8%. We also report the discovery of a dozen pillar-like structures, which are confirmed to be sites of small scale triggered star formation.