- ID:
- ivo://CDS.VizieR/J/AJ/144/95
- Title:
- Abundance in stars of the outer galactic disk. IV.
- Short Name:
- J/AJ/144/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities and chemical abundances for nine stars in the old, distant open clusters Be18, Be21, Be22, Be32, and PWM4. For Be18 and PWM4, these are the first chemical abundance measurements. Combining our data with literature results produces a compilation of some 68 chemical abundance measurements in 49 unique clusters. For this combined sample, we study the chemical abundances of open clusters as a function of distance, age, and metallicity. We confirm that the metallicity gradient in the outer disk is flatter than the gradient in the vicinity of the solar neighborhood. We also confirm that the open clusters in the outer disk are metal-poor with enhancements in the ratios [{alpha}/Fe] and perhaps [Eu/Fe]. All elements show negligible or small trends between [X/Fe] and distance (<0.02dex/kpc), but for some elements, there is a hint that the local (R_GC_<13kpc) and distant (R_GC_>13kpc) samples may have different trends with distance. There is no evidence for significant abundance trends versus age (<0.04dex/Gyr). We measure the linear relation between [X/Fe] and metallicity, [Fe/H], and find that the scatter about the mean trend is comparable to the measurement uncertainties. Comparison with solar neighborhood field giants shows that the open clusters share similar abundance ratios [X/Fe] at a given metallicity. While the flattening of the metallicity gradient and enhanced [{alpha}/Fe] ratios in the outer disk suggest a chemical enrichment history different from that of the solar neighborhood, we echo the sentiments expressed by Friel et al. that definitive conclusions await homogeneous analyses of larger samples of stars in larger numbers of clusters. Arguably, our understanding of the evolution of the outer disk from open clusters is currently limited by systematic abundance differences between various studies.
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- ID:
- ivo://CDS.VizieR/J/ApJ/710/597
- Title:
- Accretion in disks in Cep OB2
- Short Name:
- J/ApJ/710/597
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accretion rates for a large number of solar-type stars in the Cep OB2 region, based on U-band observations. Our study comprises 95 members of the ~4Myr old cluster Tr 37 (including 20 "transition" objects (TOs)), as well as the only classical T Tauri star (CTTS) in the ~12Myr old cluster NGC 7160. The stars show different disk morphologies, with the majority of them having evolved and flattened disks. The typical accretion rates are about 1 order of magnitude lower than in regions aged 1-2Myr, and we find no strong correlation between disk morphology and accretion rates. Although half of the TOs are not accreting, the median accretion rates of normal CTTS and accreting "transition" disks are similar (~3x10^-9^ and 2x10^-9^M_{sun}_/yr, respectively). Comparison with other regions suggests that the TOs observed at different ages do not necessarily represent the same type of objects, which is consistent with the fact that the different processes that can lead to reduced IR excess/inner disk clearing (e.g., binarity, dust coagulation/settling, photoevaporation, giant planet formation) do not operate on the same timescales.
- ID:
- ivo://CDS.VizieR/J/A+A/455/903
- Title:
- ACIS-I observations of NGC 2264
- Short Name:
- J/A+A/455/903
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper's goal is to improve the member census of the NGC 2264 star-forming region and study the origin of X-ray activity in young PMS stars. We analyze a deep, 100ks long, Chandra ACIS observation covering a 17'x17' field in NGC 2264. The preferential detection in X-rays of low-mass PMS stars gives strong indications of their membership. We study X-ray activity as a function of stellar and circumstellar characteristics by correlating the X-ray luminosities, temperatures, and absorptions with optical and near-infrared data from the literature.
- ID:
- ivo://CDS.VizieR/J/AJ/154/69
- Title:
- ACRONYM II. The {beta} Pictoris Moving Group
- Short Name:
- J/AJ/154/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We confirm 66 low-mass stellar and brown dwarf systems (K7-M9) plus 19 visual or spectroscopic companions of the {beta} Pictoris moving group (BPMG). Of these, 41 are new discoveries, increasing the known low-mass members by 45%. We also add four objects to the 14 known with masses predicted to be less than 0.07 M_{sun}_. Our efficient photometric + kinematic selection process identified 104 low-mass candidates, which we observed with ground-based spectroscopy. We collected infrared observations of the latest spectral types (>M5) to search for low-gravity objects. These and all <M5 candidates were observed with high-resolution optical spectrographs to measure the radial velocities and youth indicators, such as lithium absorption and H{alpha} emission, needed to confirm BPMG membership, achieving a 63% confirmation rate. We also compiled the most complete census of BPMG membership, with which we tested the efficiency and false-membership assignments using our selection and confirmation criteria. Using the new census, we assess a group age of 22+/-6 Myr, consistent with past estimates. With the now-densely sampled lithium depletion boundary, we resolve the broadening of the boundary by either an age spread or astrophysical influences on lithium-burning rates. We find that 69% of the now-known members with AFGKM primaries are M stars, nearing the expected value of 75%. However, the new initial mass function for the BPMG shows a deficit of 0.2-0.3 M_{sun}_ stars by a factor of ~2. We expect that the AFGK census of the BPMG is also incomplete, probably due to biases of searches toward the nearest stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/795/161
- Title:
- Activity and rotation in Praesepe and the Hyades
- Short Name:
- J/ApJ/795/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Open clusters are collections of stars with a single, well-determined age, and can be used to investigate the connections between angular-momentum evolution and magnetic activity over a star's lifetime. We present the results of a comparative study of the relationship between stellar rotation and activity in two benchmark open clusters: Praesepe and the Hyades. As they have the same age and roughly solar metallicity, these clusters serve as an ideal laboratory for testing the agreement between theoretical and empirical rotation-activity relations at ~600 Myr. We have compiled a sample of 720 spectra - more than half of which are new observations - for 516 high-confidence members of Praesepe; we have also obtained 139 new spectra for 130 high-confidence Hyads. We have also collected rotation periods (P_rot_) for 135 Praesepe members and 87 Hyads. To compare H{alpha} emission, an indicator of chromospheric activity, as a function of color, mass, and Rossby number R_o_, we first calculate an expanded set of {chi} values, with which we can obtain the H{alpha} to bolometric luminosity ratio, L_H{alpha}_/L_bol_, even when spectra are not flux-calibrated and/or stars lack reliable distances. Our {chi} values cover a broader range of stellar masses and colors (roughly equivalent to spectral types from K0 to M9), and exhibit better agreement between independent calculations, than existing values. Unlike previous authors, we find no difference between the two clusters in their H{alpha} equivalent width or L_H{alpha}_/L_bol_ distributions, and therefore take the merged H{alpha} and P_rot_ data to be representative of 600 Myr old stars. Our analysis shows that H{alpha} activity in these stars is saturated for R_O_<=0.11\-0.03_^+0.02^. Above that value activity declines as a power-law with slope {beta}=0.73_-0.12_^+0.16^, before dropping off rapidly at R_o_{approx} 0.4. These data provide a useful anchor for calibrating the age-activity-rotation relation beyond 600 Myr.
- ID:
- ivo://CDS.VizieR/J/ApJ/697/1578
- Title:
- A debris disk study of Praesepe
- Short Name:
- J/ApJ/697/1578
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 24um photometry of the intermediate-age open cluster Praesepe. We assemble a catalog of 193 probable cluster members that are detected in optical databases, the Two Micron All Sky Survey (2MASS), and at 24um, within an area of ~2.47deg^2^. Mid-IR excesses indicating debris disks are found for one early-type and for three solar-type stars. Corrections for sampling statistics yield a 24um excess fraction (debris disk fraction) of 6.5%+/-4.1% for luminous and 1.9%+/-1.2% for solar-type stars. The incidence of excesses is in agreement with the decay trend of debris disks as a function of age observed for other cluster and field stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/787/108
- Title:
- Age estimates for massive SFR stellar populations
- Short Name:
- J/ApJ/787/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A major impediment to understanding star formation in massive star-forming regions (MSFRs) is the absence of a reliable stellar chronometer to unravel their complex star formation histories. We present a new estimation of stellar ages using a new method that employs near-infrared (NIR) and X-ray photometry, Age_JX_. Stellar masses are derived from X-ray luminosities using the L_X_-M relation from the Taurus cloud. J-band luminosities are compared to mass-dependent pre-main-sequence (PMS) evolutionary models to estimate ages. Age_JX_ is sensitive to a wide range of evolutionary stages, from disk-bearing stars embedded in a cloud to widely dispersed older PMS stars. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) project characterizes 20 OB-dominated MSFRs using X-ray, mid-infrared, and NIR catalogs. The Age_JX_ method has been applied to 5525 out of 31784 MYStIX Probable Complex Members. We provide a homogeneous set of median ages for over 100 subclusters in 15 MSFRs; median subcluster ages range between 0.5 Myr and 5 Myr. The important science result is the discovery of age gradients across MYStIX regions. The wide MSFR age distribution appears as spatially segregated structures with different ages. The Age_JX_ ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed populations. The NIR color index J-H, a surrogate measure of extinction, can serve as an approximate age predictor for young embedded clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/122
- Title:
- Ages and masses for 920 LMC clusters
- Short Name:
- J/ApJ/751/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new age and mass estimates for 920 stellar clusters in the Large Magellanic Cloud (LMC) based on previously published broadband photometry and the stellar cluster analysis package, MASSCLEANage. Expressed in the generic fitting formula, d^2^N/dMdt{prop.to}M^{alpha}^t^{beta}^, the distribution of observed clusters is described by {alpha}=-1.5 to -1.6 and {beta}=-2.1 to -2.2. For 288 of these clusters, ages have recently been determined based on stellar photometric color-magnitude diagrams, allowing us to gauge the confidence of our ages. The results look very promising, opening up the possibility that this sample of 920 clusters, with reliable and consistent age, mass, and photometric measures, might be used to constrain important characteristics about the stellar cluster population in the LMC. We also investigate a traditional age determination method that uses a {chi}^2^ minimization routine to fit observed cluster colors to standard infinite-mass limit simple stellar population models. This reveals serious defects in the derived cluster age distribution using this method. The traditional {chi}^2^ minimization method, due to the variation of U, B, V, R colors, will always produce an overdensity of younger and older clusters, with an underdensity of clusters in the log(age/yr)=[7.0,7.5] range. Finally, we present a unique simulation aimed at illustrating and constraining the fading limit in observed cluster distributions that includes the complex effects of stochastic variations in the observed properties of stellar clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/1028
- Title:
- alpha Per cluster possible members
- Short Name:
- J/MNRAS/457/1028
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained membership probabilities of stars within a field of from the centre of the open cluster alpha Persei using proper motions and photometry from the PPMXL and Wide-field Infrared Survey Explorer catalogues. We have identified 810 possible stellar members of alpha Persei. We derived the global and radial present-day mass function (MF) of the cluster and found that they are well matched by two-stage power-law relations with different slopes at different radii. The global MF of alpha Persei shows a turnover at m=0.62M_{sun}_ with low- and high-mass slopes of {alpha}_low_=0.50+/-0.09 (0.1<m/M_{sun}_<0.62) and {alpha}_high_=2.32+/-0.14 (0.62<=m/M_{sun}_<4.68), respectively. The high-mass slope of the cluster increases from 2.01 inside 110 to 2.63 outside 22, whereas the mean stellar mass decreases from 0.95 to 0.57M_{sun}_ in the same regions, signifying clear evidence of mass segregation in the cluster. From an examination of the high-quality colour-magnitude data of the cluster and performing a series of Monte Carlo simulations, we obtained a binary fraction of fbin=34+/-12 per cent for stars with 0.70<m/M_{sun}_<4.68. This is significantly larger than the observed binary fraction, indicating that this open cluster contains a large population of unresolved binaries. Finally, we corrected the MF slopes for the effect of unresolved binaries and found low- and high-mass slopes of {alpha}_low_=0.89+/-0.11 and {alpha}_high_=2.37+/-0.09 and a total cluster mass of 352M_{sun}_ for alpha Persei.
- ID:
- ivo://CDS.VizieR/J/A+A/395/813
- Title:
- Alpha Per faint stars photometry
- Short Name:
- J/A+A/395/813
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep, wide-field optical survey of the young stellar cluster Alpha Per, in which we have discovered a large population of candidate brown dwarfs. Subsequent infrared photometric follow-up shows that the majority of them are probable or possible members of the cluster, reaching to a minimum mass of 0.035M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AJ/156/94
- Title:
- APOGEE and Gaia DR2 analysis of IC 166
- Short Name:
- J/AJ/156/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IC 166 is an intermediate-age open cluster (OC) (~1 Gyr) that lies in the transition zone of the metallicity gradient in the outer disk. Its location, combined with our very limited knowledge of its salient features, make it an interesting object of study. We present the first high-resolution spectroscopic and precise kinematical analysis of IC 166, which lies in the outer disk with R_GC_~12.7 kpc. High-resolution H-band spectra were analyzed using observations from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment survey. We made use of the Brussels Automatic Stellar Parameter code to provide chemical abundances based on a line-by-line approach for up to eight chemical elements (Mg, Si, Ca, Ti, Al, K, Mn, and Fe). The {alpha}-element (Mg, Si, Ca, and whenever available Ti) abundances, and their trends with Fe abundances have been analyzed for a total of 13 high-likelihood cluster members. No significant abundance scatter was found in any of the chemical species studied. Combining the positional, heliocentric distance, and kinematic information, we derive, for the first time, the probable orbit of IC 166 within a Galactic model including a rotating boxy bar, and found that it is likely that IC 166 formed in the Galactic disk, supporting its nature as an unremarkable Galactic OC with an orbit bound to the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A26
- Title:
- Arches cluster: IR phot., extinction and masses
- Short Name:
- J/A+A/556/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic Center is the most active site of star formation in the Milky Way Galaxy, where particularly high-mass stars have formed very recently and are still forming today. However, since we are looking at the Galactic Center through the Galactic disk, knowledge of extinction is crucial to study this region. The Arches cluster is a young, massive starburst cluster near the Galactic Center. We observed the Arches cluster out to its tidal radius using Ks-band imaging obtained with NAOS/CONICA at the VLT combined with Subaro/Cisco J-band data to gain a full understanding of the cluster mass distribution. We show that the determination of the mass of the most massive star in the Arches cluster, which had been used in previous studies to establish an upper-mass limit for the star formation process in the Milky Way, strongly depends on the assumed slope of the extinction law. Assuming the two regimes of widely used infrared extinction laws, we show that the difference can reach up to 30% for individually derived stellar masses and {Delta}AKs~1 magnitude in acquired Ks-band extinction, while the present mass function slope changes by ~0.17dex. The present-day mass function slope derived assuming the Nishiyama et al. (2009) extinction law increases from a flat slope of {alpha}-Nishi=-1.50+/-0.35 in the core (r<0.2pc) to {alpha}-Nishi=-2.21+/-0.27 in the intermediate annulus (0.2<r<0.4pc), where the Salpeter slope is -2.3. The present-day mass function steepens to {alpha}-Nishi=-3.21+/-0.30 in the outer annulus (0.4<r<1.5pc), indicating that the outer cluster region is depleted of high mass stars. This picture is consistent with mass segregation due to the dynamical evolution of the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/138/1116
- Title:
- A Spitzer view of NGC 2264
- Short Name:
- J/AJ/138/1116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed mid-IR photometry of the young open cluster NGC 2264 using the images obtained with the Spitzer Space Telescope Infrared Array Camera and Multiband Imaging Photometer for Spitzer instruments and presented a normalized classification scheme of young stellar objects in various color-color diagrams to make full use of the information from multicolor photometry. These results are compared with the classification scheme based on the slope of the spectral energy distribution (SED). From the spatial distributions of Class I and II stars, we have identified two subclusterings of Class I objects in the CONE region of Sung et al. (Cat. J/AJ/135/441). The disked stars in the other star-forming region S Mon are mostly Class II objects. In addition, we have derived a somewhat higher value of the primordial disk fraction for NGC 2264 members located below the main pre-main-sequence locus (so-called BMS stars). This result supports the idea that BMS stars are young stars with nearly edge-on disks.
- ID:
- ivo://CDS.VizieR/J/PASP/116/1012
- Title:
- A star catalog for the open cluster NGC 188
- Short Name:
- J/PASP/116/1012
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new BVRI broadband photometry for the old open cluster NGC 188, based on an analysis of 299 CCD images either obtained by us, donated by colleagues, or retrieved from public archives.
- ID:
- ivo://CDS.VizieR/J/ApJ/718/810
- Title:
- Astrometry and Photometry in the Arches cluster
- Short Name:
- J/ApJ/718/810
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep Keck/NIRC2 HK'L' observations of the Arches cluster near the Galactic center reveal a significant population of near-infrared excess sources. We combine the L'-band excess observations with K'-band proper motions, which allow us to confirm cluster membership of excess sources in a starburst cluster for the first time. The robust removal of field contamination provides a reliable disk fraction down to our completeness limit of H=19mag, or ~5M_{sun}_ at the distance of the Arches. Of the 24 identified sources with K'-L'>2.0mag, 21 have reliable proper motion measurements, all of which are proper motion members of the Arches cluster. VLT/SINFONI K'-band spectroscopy of 3 excess sources reveals strong CO bandhead emission, which we interpret as the signature of dense circumstellar disks. The detection of strong disk emission from the Arches stars is surprising in view of the high mass of the B-type main sequence host stars of the disks and the intense starburst environment. We find a disk fraction of 6%+/-2% among B-type stars in the Arches cluster. A radial increase in the disk fraction from 3% to 10% suggests rapid disk destruction in the immediate vicinity of numerous O-type stars in the cluster core. A comparison between the Arches and other high- and low-mass star-forming regions provides strong indication that disk depletion is significantly more rapid in compact starburst clusters than in moderate star-forming environments.
- ID:
- ivo://CDS.VizieR/J/AJ/156/61
- Title:
- A study of the H{alpha} variability of Be stars
- Short Name:
- J/AJ/156/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the results of 4 years of high-resolution spectral observations of 69 emission-line stars, 54 of them being newly discovered sources. We classified the stars on the basis of their position in the two-color IR diagram and some additional criteria: shape and width of the H{alpha} profile, presence of He lines, proper motion and parallax, membership to open cluster and associations. Sixty of our targets turned out to be Be stars. We also found four late giants, four pre-MS stars, and one late dwarf. The H{alpha} emission profiles of our Be stars range from single peaked to typical shell profiles that can also be highly asymmetric or single-peaked profiles with a narrow absorption core. The emission profiles appear almost constant with time or highly variable in intensity and in their V/R ratio. The detected long-term variability of the H{alpha} emission is important for investigating the on/off switch phenomenon of Be stars. Our study led to an increase of the number of the emission-line stars of 16 open clusters.
- ID:
- ivo://CDS.VizieR/J/PAZh/25/115
- Title:
- A study of the open cluster NGC 6811
- Short Name:
- J/PAZh/25/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 191 individual measurements of radial velocities made with CORAVEL-type spectrometer are presented for 60 stars in the large region of NGC 6811 open cluster. Photoelectric UBVR magnitudes are given for 117 stars - members of the cluster by proper motions. Spectral classification of these stars is taken from Straizys and Kazlauskas (1993BaltA...2....1S).
- ID:
- ivo://CDS.VizieR/J/A+A/612/A79
- Title:
- Barnard 30 dark cloud IR and submm data
- Short Name:
- J/A+A/612/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The early evolutionary stage of brown dwarfs (BDs) is not very well characterized, especially during the embedded phase. Our goal is to gain insight into the dominant formation mechanism of very low-mass objects and BDs. We have conducted deep observations at 870um obtained with the LABOCA bolometer at the APEX telescope in order to identify young submillimeter (submm) sources in the Barnard 30 dark cloud. We have complemented these data with multi-wavelength observations from the optical to the far-IR and compiled complete spectral energy distributions in order to identify the counterparts, characterize the sources and to assess their membership to the association and stellar or substellar status based on the available photometric information. We have identified 34 submm sources and a substantial number of possible and probable Barnard 30 members within each individual APEX/LABOCA beam. They can be classified into three distinct groups. First, 15 of these 34 have a clear optical or IR counterpart to the submm peak and nine of them are potential proto-BD candidates. Moreover, a substantial number of them could be multiple systems. A second group of 13 sources comprises candidate members with significant infrared excesses located away from the central submm emission. All of them include BD candidates, some displaying IR excess, but their association with submm emission is unclear. In addition, we have found six starless cores and, based on the total dust mass estimate, three might be pre-substellar (or pre-BDs) cores. Finally, the complete characterization of our APEX/LABOCA sources, focusing on those detected at 24 and/or 70um, indicates that in our sample of 34 submm sources there are, at least: two WTTs, four CTTs, five young stellar objects, eight proto-BD candidates (with another three dubious cases), and one very low luminosity objects.
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/1241
- Title:
- Be 81, NGC 1917 and NGC 2141 BVI photometry
- Short Name:
- J/MNRAS/437/1241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we analyse the evolutionary status of three open clusters: NGC 1817, NGC 2141 and Berkeley 81. They are all of intermediate age, two are located in the Galactic anticentre direction while the third one is located in the Galactic Centre direction. All of them were observed with Large Binocular Camera at Large Binocular Telescope using the Bessel B, V and I filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram (CMD) method, i.e. the direct comparison of the observational CMDs with a library of synthetic CMDs generated with different evolutionary sets (Padova, FRANEC and FST). This analysis shows that NGC 1817 has subsolar metallicity, age between 0.8 and 1.2Gyr, reddening E(B-V) in the range 0.21 and 0.34 and distance modulus (m-M)_0_ of about 10.9; NGC 2141 is older, with age in the range 1.25 and 1.9Gyr, E(B-V) between 0.36 and 0.45, (m-M)_0_ between 11.95 and 12.21 and subsolar metallicity; Berkeley 81 has metallicity about solar, with age between 0.75 and 1.0Gyr, has reddening E(B-V)~0.90 and distance modulus (m-M)_0~12.4. Exploiting the large field of view of the instrument we derive the structure parameters for NGC 2141 and Berkeley 81 by fitting a King profile to the estimated density profile. Combining this information with the synthetic CMD technique we estimate a lower limit for the cluster total mass for these two systems.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/429
- Title:
- Berkeley 94 and Berkeley 96 UBVRcIcJHKs
- Short Name:
- J/MNRAS/435/429
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed multiband UBVRcIcJHKs photometry of two young clusters located at large Galactocentric distances in the direction of the Perseus spiral arm. The obtained distances and colour excesses amount to 3.9+/-0.11kpc, E(B-V)=0.62+/-0.05 for Berkeley 94, and 4.3+/-0.15kpc, E(B-V)=0.58+/-0.06 for Berkeley 96. The respective ages, as measured from the comparison of the upper colour-magnitude diagrams to model isochrones, amount to log10Age(yr)=7.5+/-0.07 and 7.0+/-0.07, respectively. A sequence of optical pre-main-sequence (PMS) members is proposed in both clusters. In addition, samples of objects showing (H-Ks) excess are found. Part of these are suggested to be PMS cluster members of lower mass than the optical candidates. The spatial distribution of these sources, the comparison to Galactic models and to the expected number of contaminating distant red galaxies, and the spectral energy distribution in particular cases support this suggestion. The spatial distributions shown by members in different mass ranges can be interpreted in terms of the results from numerical simulations. According to these, different initial conditions and evolutionary dynamical paths are suggested for the clusters. Berkeley 94 would have formed under supervirial conditions, and followed the so-called warm collapse model in its evolution, whereas Berkeley 96 would have formed with a subvirial structure, and would have evolved following a cold collapse path. Both processes would be able to reproduce the suggested degree of mass segregation and their spatial distribution by mass range. Finally, the mass distributions of the clusters, from the most massive stars down to PMS stars around 1.3M_{sun}_, are calculated. An acceptable general agreement with the Salpeter initial mass function slope is found.
- ID:
- ivo://CDS.VizieR/J/A+AS/122/111
- Title:
- Berkeley 64 and 69 stars UBVRI photometry
- Short Name:
- J/A+AS/122/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVRI CCD photometry for previously unstudied open clusters (Be 64 and Be 69). Photometry has also been carried out for nearby fields to correct f or the effects of field stars contamination. From the colour-colour diagram the reddening for Be 64 and Be 69 is estimated to be ~1.05mag and ~0.65mag respectively. In case of Be 69 the comparison of observational colour-magnitude diagram (CMD) with the standard isochrones of VandenBerg (19855ApJS...58..711V) indicates an apparent discrepancy between the shape of the turnoff and isochrones. The morphological features of the CMDs of Be 69 are better understood in terms of convective overshooting. The comparison of CMDs of both the clusters with the convective overshoot models (Bertelli et al. 1994A&AS..106..275B) produces a good fit for a metallicity Z=0.008 and age =0.8-1.0Gyr. An apparent distance modulus (m-M)=16.2 and 14.3 has been estimated for Be 64 and Be 69, respectively, which corresponds to a distance of 3880+/-480pc and 2860+/-310pc, respectively.
- ID:
- ivo://CDS.VizieR/J/MNRAS/299/834
- Title:
- Berkeley 21 BVI photometry
- Short Name:
- J/MNRAS/299/834
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD BVI photometry of the old open cluster Berkeley 21, one of the most distant clusters in the Galactic anticentre direction, and possibly the lowest metallicity object in the open clusters sample. Its position and metal abundance make it very important for the study of the Galactic disc. Using the synthetic colour-magnitude diagram method, we estimate values for the distance modulus (m-M)_0_=13.4-13.6, reddening E(B-V)=0.74-0.78 (with possible differential absorption), and age= 2.2-2.5Gyr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/368/471
- Title:
- Berkeley 32 BVI photometry and spectroscopy
- Short Name:
- J/MNRAS/368/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained medium- and low-resolution spectroscopy and BVI CCD imaging of Berkeley 32, an old open cluster which lies in the anticentre direction. From the radial velocities of 48 stars in the cluster direction, we found that 31 of them, in crucial evolutionary phases, are probable cluster members, with an average radial velocity of +106.7(sigma=8.5)km/s . From isochrone fitting to the colour-magnitude diagrams of Berkeley 32, we have obtained an age of 6.3Gyr, (m-M)0=12.48 and E(B-V)=0.10. The best fit is obtained with Z=0.008. A consistent distance, (m-M)_0_~=12.6+/-0.1, has been derived from the mean magnitude of red clump stars with confirmed membership; we may assume (m-M)_0_~=12.55+/-0.1. The colour-magnitude diagram of the nearby field observed to check for field stars contamination looks intriguingly similar to that of the Canis Major overdensity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/784
- Title:
- Berkeley 90. III. Cluster parameters
- Short Name:
- J/MNRAS/465/784
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The open cluster Berkeley 90 is the home to one of the most massive binary systems in the Galaxy, LS III +46 11, formed by two identical, very massive stars (O3.5 If* + O3.5 If*), and a second early-O system (LS III +46 12 with an O4.5 IV((f)) component at least). Stars with spectral types earlier than O4 are very scarce in the Milky Way, with no more than 20 examples. The formation of such massive stars is still an open question today, and thus the study of the environments where the most massive stars are found can shed some light on this topic. To this aim, we determine the properties and characterize the population of Berkeley 90 using optical, near-infrared and WISE photometry and optical spectroscopy. This is the first determination of these parameters with accuracy. We find a distance of 3.5+/-0.5kpc and a maximum age of 3Ma. The cluster mass is around 1000M_{sun}_ (perhaps reaching 1500M_{sun}_ if the surrounding population is added), and we do not detect candidate runaway stars in the area. There is a second population of young stars to the Southeast of the cluster that may have formed at the same time or slightly later, with some evidence for low-activity ongoing star formation.
- ID:
- ivo://CDS.VizieR/J/AJ/155/91
- Title:
- Be stars in open clusters with PTF/iPTF. I.
- Short Name:
- J/AJ/155/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a search for Be star candidates in open clusters using H{alpha} imaging photometry of the Palomar Transient Factory Survey to investigate some connections among Be star phenomena, cluster environments, and ages. Stellar members of clusters were identified by spatial distributions, near-infrared magnitudes and colors, and by proper motions. Among 104 open clusters, we identified 96 Be star candidates in 32 clusters; 11 of our candidates have been reported in previous studies. We found that the clusters with age 7.5<log(t(year))=<8.5 tend to have more Be star candidates; there is about a 40% occurrence rate within this age bin. The clusters in this age bin also tend to have a higher Be fraction N(Be)/N(Be+B-type). These results suggest that the environments of young and intermediate clusters are favorable to the formation of Be phenomena. Spatial distribution of Be star candidates with different ages implies that they do not form preferentially in the central regions. Furthermore, we showed that the mid-infrared (MIR) colors of the Be star candidates are similar to known Be stars, which could be caused by free-free emission or bound-free emission. Some Be star candidates might have no circumstellar dust according to their MIR colors. Finally, among 96 Be candidates, we discovered that one Be star candidate FSR 0904-1 exhibits long-term variability on the timescale of ~2000 days with an amplitude of 0.2-0.3 mag, indicating a long timescale of disk evolution.
- ID:
- ivo://CDS.VizieR/J/AJ/161/160
- Title:
- BINOCS: NEWFIRM & IRAC IR photometry of clusters
- Short Name:
- J/AJ/161/160
- Date:
- 18 Jan 2022
- Publisher:
- CDS
- Description:
- We introduce a new binary detection technique, Binary INformation from Open Clusters using SEDs (binocs), which we show is able to determine reliable stellar multiplicity and masses over a much larger mass range than current approaches. This new technique determines accurate component masses of binary and single systems of the open clusters' main sequence by comparing observed magnitudes from multiple photometric filters to synthetic star spectral energy distributions (SEDs), allowing us to systematically probe the binary population for low-mass stars in clusters for eight well-studied open clusters. We provide new deep, infrared photometric catalogs (1.2-8.0 {mu}m) for the key open clusters NGC 1960 (M36), NGC 2099 (M37), NGC 2420, and NGC 2682 (M67), using observations from NOAO/NEWFIRM and Spitzer/IRAC. Using these deep multiwavelength catalogs, the binocs method is applied to these clusters to determine accurate component masses for unresolved cluster binaries. We explore binary fractions as a function of cluster age, Galactic location, and metallicity.
- ID:
- ivo://CDS.VizieR/J/A+A/521/A18
- Title:
- Blue stars with disk photometry in NGC 6611
- Short Name:
- J/A+A/521/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6611 and its parental cloud, the Eagle Nebula (M 16), are well-studied star-forming regions, thanks to their large content of both OB stars and stars with disks and the observed ongoing star formation. In our previous studies of the Eagle Nebula, we identified 834 disk-bearing stars associated with the cloud, after detecting their excesses in NIR bands from J band to 8.0um. In this paper, we study in detail the nature of a subsample of disk-bearing stars that show peculiar characteristics. They appear older than the other members in the V vs. V-I diagram, and/or they have one or more IRAC colors at pure photospheric values, despite showing NIR excesses, when optical and infrared colors are compared.
- ID:
- ivo://CDS.VizieR/J/A+A/463/789
- Title:
- Blue stragglers in open clusters
- Short Name:
- J/A+A/463/789
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of blue-straggler candidates in galactic open clusters. It is based on the inspection of the colour-magnitude diagrams of the clusters, and it updates and supersedes the first version (Ahumada & Lapasset, 1995, Cat. <J/A+AS/109/375>). A new bibliographical search was made for each cluster, and the resulting information is organised into two tables. Some methodological aspects have been revised, in particular those concerning the delimitation of the area in the diagrams where the stragglers are selected. A total of 1887 blue-straggler candidates have been found in 427 open clusters of all ages, doubling the original number. The catalogued stars are classified into two categories mainly according to membership information.
- ID:
- ivo://CDS.VizieR/J/A+A/466/917
- Title:
- Brightest stars of sigma Orionis cluster
- Short Name:
- J/A+A/466/917
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The very young sigma Orionis cluster (about 3Ma) is a cornerstone for the understanding of the formation of stars and substellar objects down to planetary masses. However, its stellar population is far to be completely known. This study has the purpose of identifying and characterising the most massive stars of sigma Orionis to complement current and future deep searches for brown dwarfs and planetary-mass objects in the cluster. I have cross-correlated the sources in the Tycho and 2MASS catalogues in a region of 30arcmin radius with centre in the O-type star sigma Ori A. In the area, I have studied the membership in the Ori OB 1b Association of the brightest stars in the optical using astrometric, X-ray and infrared and optical photometric data from public catalogues and spectroscopic data from the literature. A list of 26 young stars, four candidate young stars and 16 probable foreground stars has arised from the study. Seven young stars probably harbour discs (four are new). There is no mass-dependence of the disc frequency in the cluster. I have derived for the first time the mass spectrum in sigma Orionis from 1.1 to 24M_{sun}_ (alpha=+2.0^+0.2^_-0.1_; roughly Salpeter-like). I have also provided additional proofs on the existence of several spatially superimposed stellar populations in the direction of sigma Orionis. Finally, the cluster may be closer and older than previously considered.
- ID:
- ivo://CDS.VizieR/J/other/NewA/11.262
- Title:
- BVIc photometry in Lynga 11
- Short Name:
- J/other/NewA/11.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained CCD BVI_KC_ photometry down to V~21.5 for the open cluster Lynga 11 and its surrounding field. This previously unstudied object appears to be rich and highly absorbed. A cluster angular radius of 4.5+/-0.5, equivalent to (3.0+/-0.3)pc, is estimated from star counts in 100-pixel a side boxes distributed throughout the whole observed field. Our analysis suggests that Lynga 11 is moderately young and probably of solar metallicity.
- ID:
- ivo://CDS.VizieR/J/AJ/140/677
- Title:
- BVIc photometry of IC 4665
- Short Name:
- J/AJ/140/677
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new, BVIc photometric survey of the young open cluster IC 4665, which improves on previous studies of this young cluster by incorporating a rigorous standardization procedure, thus providing high-fidelity colors and magnitudes for cluster members. We use this new photometric dataset to reevaluate the properties (age and distance) of IC 4665.
- ID:
- ivo://CDS.VizieR/J/PASJ/56/295
- Title:
- BVIc photometry of old open clusters
- Short Name:
- J/PASJ/56/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new photometric data for 14 galactic open clusters taken by the 65cm telescope at Gunma Astronomical Observatory. They were in the anti-galactic center region selected from the Catalog of Open Cluster Data (Lynga, 1987, See Cat. <J/A+A/438/1163>). We estimated the parameters of the clusters, i.e., age, metallicity, distance, and reddening, by fitting Padova isochrones to the color-magnitude diagram.
- ID:
- ivo://CDS.VizieR/J/MNRAS/391/1482
- Title:
- BVIc photometry of Trumpler 20
- Short Name:
- J/MNRAS/391/1482
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We show that the open cluster Trumpler 20, contrary to the earlier findings, is actually an old Galactic open cluster. New CCD photometry and high-resolution spectroscopy are used to derive the main parameters of this cluster. At [Fe/H]=-0.11 for a single red giant star, the metallicity is slightly subsolar. The best fit to the colour-magnitude diagrams is achieved using a 1.3-Gyr isochrone with convective overshoot. The cluster appears to have a significant reddening at E(B-V)=0.46 (for B0 spectral type), although for red giants this high reddening yields the colour temperature exceeding the spectroscopic Teff by about 200K. Trumpler 20 is a very rich open cluster, containing at least 700 members brighter than M_V_=+4. It may extend over the field of view available in our study at 20x20arcmin^2^.
- ID:
- ivo://CDS.VizieR/J/A+A/417/945
- Title:
- BVI & JHK photometry of NGC 3960
- Short Name:
- J/A+A/417/945
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a BVI photometric and astrometric catalogue of the open cluster NGC 3960, down to limiting magnitude V~22, obtained from observations taken with the Wide Field Imager camera at the MPG/ESO 2.2m Telescope at La Silla. The photometry of all the stars detected in our field of view has been used to estimate a map of the strong differential reddening affecting this area. Our results indicate that, within the region where the cluster dominates, the E(V-I) values range from 0.21 up to 0.78, with E(V-I)=0.36 (E(B-V)=0.29) at the nominal cluster centroid position; color excesses E(V-I) up to 1 mag have been measured in the external regions of the field of view where field stars dominate. The reddening-corrected color-magnitude diagram (CMD) allows us to conclude that the cluster has an age between 0.9 and 1.4Gyr and a distance modulus of (V-M_V)_0=11.35. Based on observations made with the European Southern Observatory telescopes obtained from the the ESO/ST-ECF Science Archive Facility.
- ID:
- ivo://CDS.VizieR/J/A+A/484/609
- Title:
- BVI photometry and proper motions in M67
- Short Name:
- J/A+A/484/609
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The solar-age open cluster M 67 (C0847+ 120, NGC 2682) is a touchstone in studies of the old Galactic disk. Despite its outstanding role, the census of cluster membership for M 67 at fainter magnitudes and their properties are not well-established. Using proprietary and archival ESO data, we have obtained astrometric, photometric, and radial velocities of stars in a 34x33arcmin^2^ field centered on the old open cluster M 67. The two-epoch archival observations separated by 4-years and acquired with the Wide-Field Imager at the 2.2m MPG/ ESO telescope were reduced with our new astrometric techniques, as described in the first paper in this series (Anderson et al., 2006A&A...454.1029A). The same observations served to derive calibrated BVI photometry in M 67. Radial velocities were measured using the archival and new spectroscopic data obtained at the VLT.
- ID:
- ivo://CDS.VizieR/J/A+A/442/917
- Title:
- BVI photometry in Berkeley 73, 75 and 25
- Short Name:
- J/A+A/442/917
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD BVI photometry of the faint open clusters Berkeley 73, Berkeley 75 and Berkeley 25 are presented. The two latter are previously unstudied clusters to our knowledge. While Berkeley 73 is found to be of intermediate-age (about 1.5Gyr old), Berkeley 75 and Berkeley 25 are old clusters, with ages greater than 3.0Gyr. We provide also estimates of the clusters size. All these clusters lie far away from the Galactic Center, at R_GC_>=16kpc, and quite high on the Galactic plane, at |Z_{sun}_|>=1.5kpc. They are therefore important targets to probe the properties of the structure of the Galaxy in this direction, where the Canis Major over-density has been discovered to be located.
- ID:
- ivo://CDS.VizieR/J/A+A/462/245
- Title:
- BVI photometry in NGC 6611
- Short Name:
- J/A+A/462/245
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observation of young stars with circumstellar disks suggests that the disks are dissipated, starting from the inner region, by the radiation of the central star and eventually by the formation of rocky planetesimals, over a time scale of several million years. It was also shown that strong UV radiation emitted by nearby massive stars can heat a circumstellar disk up to some thousand degrees, inducing the photoevaporation of the gas. This process strongly reduces the dissipation time scale. We study whether there exists a correlation between the spatial distribution of stars with circumstellar disks and the position of massive stars with spectral class earlier than B5, in the open cluster NGC 6611. We created a multiband catalog of the cluster, down to V~23mag, using optical data from a WFI observation at 2.2m of ESO in the BVI bands, the 2MASS public point source catalog and an archival X-ray observation made with CHANDRA/ACIS. We selected the stars with infrared excess (due to the emission of a circumstellar disk) using suitable color indices independent of extinction, and studied their spatial distribution.
- ID:
- ivo://CDS.VizieR/J/PASP/115/413
- Title:
- BVI photometry in the open cluster NGC 6791
- Short Name:
- J/PASP/115/413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present broadband BVI photometry for the open cluster NGC 6791, based upon analysis of 1764 individual CCD images. Data tables listing measured magnitudes and standard errors, image-quality indices, a variability index, and equinox J2000.0 equatorial coordinates for 14,342 stars to V~24 have been made available to the public through the services of the Canadian Astronomy Data Centre. Equatorial coordinates only have been provided for a further 1916 stars, the photometry for which we were unable to calibrate because of lack of color information.
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/1132
- Title:
- BVI photometry of Be 27, Be 24 and Be 36
- Short Name:
- J/MNRAS/424/1132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the investigation of the evolutionary status of three open clusters: Berkeley 27, Berkeley 34 and Berkeley 36, all located in the Galactic anticentre direction. All of them were observed with SUperb Seeing Imager 2 at the New Technology Telescope using the Bessel B, V and I filters.
- ID:
- ivo://CDS.VizieR/J/AJ/141/92
- Title:
- BVI photometry of 10 distant open clusters
- Short Name:
- J/AJ/141/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The oldest open star clusters are important for tracing the history of the Galactic disk, but many of the more distant clusters are heavily reddened and projected against the rich stellar background of the Galaxy. We have undertaken an investigation of several distant clusters (Berkeley 19, Berkeley 44, King 25, NGC 6802, NGC 6827, Berkeley 52, Berkeley 56, NGC 7142, NGC 7245, and King 9) to develop procedures for separating probable cluster members from the background field. We next created a simple quantitative approach for finding approximate cluster distances, reddenings, and ages. We first conclude that with the possible exception of King 25 they are probably all physical clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/335/291
- Title:
- BVI photometry of NGC 2547
- Short Name:
- J/MNRAS/335/291
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have developed the techniques required to use Naylor's optimal photometry algorithm of to create colour-magnitude diagrams with well-defined completeness functions. To achieve this we first demonstrate that the optimal extraction is insensitive to uncertainties in the measured position of the star. We then show how to correct the optimally extracted fluxes such that they correspond to those measured in a large aperture, so aperture photometry of standard stars can be used to place the measurements on a standard system. The technique simultaneously removes the effects of a position-dependent point spread function. Finally, we develop a method called 'ghosting', which calculates the completeness corrections in the absence of an accurate description of the point spread function. We apply these techniques to the young cluster NGC 2547 (=C0809-491), and use an X-ray-selected sample to find an age of 20-35Myr and an intrinsic distance modulus of 8.00-8.15mag. We use these isochrones to select members from our photometric surveys. Our derived luminosity function shows a well-defined Wielen dip, making NGC 2547 the youngest cluster in which such a feature has been observed. Our derived mass function spans the range 0.1-6M_{sun}_ and is similar to that for the field and the older, more massive clusters M35 and the Pleiades, supporting the idea of a universal initial mass function.
- ID:
- ivo://CDS.VizieR/J/MNRAS/377/1737
- Title:
- BVI photometry of NGC 2489
- Short Name:
- J/MNRAS/377/1737
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD BVI photometry for the southern open cluster NGC 2489 and its surrounding field. The sample consists of 2182 stars measured in an area of 13.6'x13.6', extending down to V~21.5. These data are supplemented with CORAVEL radial-velocity observations for seven red giant candidates. A cluster angular radius of 6.7+/-0.6', equivalent to 3.5+/-0.3pc, is estimated from star counts carried out inside and outside the cluster region. The comparison of the cluster colour-magnitude diagrams with isochrones of the Padova group yields E(B-V)=0.30+/-0.05, E(V-I)=0.40+/-0.05 and V-MV=12.20+/-0.25 for logt=8.70 (t=500^+130^_-100_Myr) and Z=0.019. NGC 2489 is then located at 1.8+/-0.3kpc from the Sun and 25pc below the Galactic plane. The analysis of the kinematical data allowed us to confirm cluster membership for six red giants, one of them being a spectroscopic binary. A mean radial velocity of 38.13+/-0.33km/s was derived for the cluster red giants. The properties of a sample of open clusters aligned along the line of sight of NGC 2489 are examined.
- ID:
- ivo://CDS.VizieR/J/MNRAS/367/599
- Title:
- BVI photometry of NGC 5288
- Short Name:
- J/MNRAS/367/599
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present charge-coupled device (CCD) images in the Johnson B and V and Kron-Cousins I passbands for the previously unstudied open cluster NGC 5288. The sample consists of 15688 stars reaching down to V~20.5. The cluster appears to have a relatively small but conspicuous nucleus and a low-density extended coronal region.
- ID:
- ivo://CDS.VizieR/J/MNRAS/364/179
- Title:
- BVI photometry of 8 open clusters
- Short Name:
- J/MNRAS/364/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD BVI photometry is presented for eight previously unstudied star clusters located in the first and fourth Galactic quadrants: AL 1, BH 150, NGC 5764, Lynga 9, Czernik 37, BH 261, Berkeley 80 and King 25. Colour-magnitude diagrams of the cluster regions suggest that several of them (BH 150, Lynga 9, Czernik 37, BH 261 and King 25) are so embedded in the dense stellar population toward the galactic centre that their properties, or even their existence as physical systems, cannot be confirmed. Lynga 9, BH 261 and King 25 appear to be slight enhancements of dense star fields, BH 150 is probably just a single bright star in a dense field and Czernik 37 may be a sparse, but real cluster superimposed on the galactic bulge population. We derive preliminary estimates of the physical parameters for the remaining clusters. AL 1 appears to be an intermediate-age cluster beyond the solar circle on the far side of the galaxy and the final two clusters, NGC 5764 and Berkeley 80, are also of intermediate age but located inside the solar ring. This set of clusters highlights the difficulties inherent in studying the stellar populations toward the inner regions of the galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/360/655
- Title:
- BVI photometry of 3 open clusters
- Short Name:
- J/MNRAS/360/655
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on BVI CCD photometry to V=22.0 for three fields centred on the region of the Galactic star clusters Ruprecht 4, Ruprecht 7 and Pismis 15 and on three displaced control fields.
- ID:
- ivo://CDS.VizieR/J/A+A/370/931
- Title:
- BVI photometry of 4 open clusters
- Short Name:
- J/A+A/370/931
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD observations in the B, V and I passbands have been used to generate colour-magnitude diagrams reaching down to V~19mag for two slightly characterized (Melotte 105 and Hogg 15) and two almost unstudied (Pismis 21 and Ruprecht 140) open clusters. The sample consists of about 1300 stars observed in fields of about 4'x4'. Our analysis shows that neither Pismis 21 nor Ruprecht 140 are genuine open clusters since no clear main sequences or other meaningful features can be seen in their colour-magnitude diagrams. Melotte 105 and Hogg 15 are open clusters affected by E(B-V)=0.42+/-0.03 and 0.95+/-0.05, respectively. Their distances to the Sun have been estimated as 2.2+/-0.3 and 2.6+/-0.08kpc, respectively, while the corresponding ages estimated from empirical isochrones fitted to the Main Sequence cluster members are ~350Myr and 300Myr, respectively. The present data are not consistent with the membership of the WN6 star HDE 311884 to Hogg 15.
- ID:
- ivo://CDS.VizieR/J/AJ/148/30
- Title:
- BVI photometry of 350 Pleiades stars
- Short Name:
- J/AJ/148/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new BVI_C_ photometry for 350 Pleiades proper motion members with 9<V<~17. Importantly, our new catalog includes a large number of K- and early M-type stars, roughly doubling the number of low-mass stars with well-calibrated Johnson/Cousins photometry in this benchmark cluster. We combine our new photometry with existing photometry from the literature to define a purely empirical isochrone at Pleiades age ({approx}100Myr) extending from V=9 to 17. We use the empirical isochrone to identify 48 new probable binaries and 14 likely nonmembers. The photometrically identified single stars are compared against their expected positions in the color-magnitude diagram (CMD). At 100Myr, the mid K and early M stars are predicted to lie above the zero-age main sequence (ZAMS) having not yet reached the ZAMS. We find in the B-V versus V CMD that mid K and early M dwarfs are instead displaced below (or blueward of) the ZAMS. Using the stars' previously reported rotation periods, we find a highly statistically significant correlation between rotation period and CMD displacement, in the sense that the more rapidly rotating stars have the largest displacements in the B-V CMD.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/1301
- Title:
- BVI photometry of six old open clusters
- Short Name:
- J/MNRAS/371/1301
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the first BVI CCD photometry of six overlooked old open clusters (Berkeley 44, NGC 6827, Berkeley 52, Berkeley 56, Skiff 1 and Berkeley 5) and derive estimates of their fundamental parameters by using isochrones from the Padova library. We found that all the clusters are older than the Hyades, with ages ranging from 0.8Gyr (NGC 6827 and Berkeley 5) to 4.0Gyr (Berkeley 56). The latter is one of the old open clusters with the largest heliocentric distance.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/L32
- Title:
- BVI photometry of the SMC star cluster ESO 51-SC09
- Short Name:
- J/ApJ/756/L32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results on the age and metallicity estimates of the astonishingly unstudied Small Magellanic Cloud (SMC) cluster (ESO 51-SC09), from CCD BVI photometry obtained at the ESO NTT with the EMMI attached. ESO 51-SC09 turns out to be a relatively small cluster (FWHM=10+/-1pc) located ~4{deg} northward from the galaxy center. We report for the first time a mean cluster age of 7.0+/-1.3Gyr and a mean cluster metallicity of [Fe/H]=-1.00+/-0.15 dex, concluding that ESO 51-SC09 belongs to the group of the oldest SMC clusters. We found that the cluster is projected onto an older (age~10-13Gyr) and more metal-poor ([Fe/H]=-1.3+/-0.2 dex) dominant field stellar population, so that the cluster could have reached its current location because of its orbital motion.
- ID:
- ivo://CDS.VizieR/J/A+A/388/179
- Title:
- BVI photometry of two open clusters
- Short Name:
- J/A+A/388/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of CCD BVI Johnson-Cousins photometry down to V~19mag in the regions of the unstudied stellar groups Pismis 23 and BH 222, both projected close to the direction towards the Galactic centre. We measured V magnitude and B-V and V-I colours for a total of 928 stars in fields of about 4'x4'.
- ID:
- ivo://CDS.VizieR/J/A+A/360/529
- Title:
- BVI photometry of 4 young open clusters
- Short Name:
- J/A+A/360/529
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD observations in the B, V, and I passbands obtained for stars in the fields of the open clusters Pismis 22, NGC 6178, NGC 6216, and Ruprecht 130, projected not far from the Galactic centre (|l|<30{deg}, |b|<2{deg}). The sample consists of about 790 stars reaching down to V~18-19mag. From the analysis of the colour magnitude diagrams, we confirmed the physical reality of the clusters and derived their reddening, distance and age. In addition, we obtained flux-calibrated integrated spectra in the range 3500-9200{AA} for the cluster sample. The equivalent widths of the Balmer lines provided us with age estimates, while the comparison with template spectra allowed us to derive both foreground reddening and age. The photometric and spectroscopic results reveal that the four studied objects are young open clusters with ages ranging between 35 and 50Myr. The clusters, located between 1.0kpc and 4.3kpc from the Sun, are affected by different amounts of interstellar visual absorption (0.6=~A_v_=~6.0).
- ID:
- ivo://CDS.VizieR/J/MNRAS/375/1220
- Title:
- BVI photometry of young stars in 10 clusters
- Short Name:
- J/MNRAS/375/1220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have selected pre-main-sequence (PMS) stars in 12 groups of notional ages ranging from 1 to 35Myr, using heterogeneous membership criteria. Using these members we have constructed empirical isochrones in V, V-I colour-magnitude diagrams. This allows us to identify clearly the gap between the radiative main sequence and the convective PMS (the RC gap). We follow the evolution of this gap with age and show that it can be a useful age indicator for groups less than =15 Myr old. We also observe a reduction in absolute spreads about the sequences with age. Finally, the empirical isochrones allow us to place the groups in order of age, independently of theory. The youngest groups can be collated into three sets of similar ages. The youngest set is the ONC, NGC 6530 and IC 5146 (nominally 1Myr); next Cep OB3b, NGC 2362, Ori and NGC 2264 (nominally 3Myr); and finally Ori and IC 348 (nominally 45Myr). This suggests Cep OB3b is younger than previously thought, and IC 348 older. For IC 348 the stellar rotation rate distribution and fraction of stars with discs imply a younger age than we derive. We suggest this is because of the absence of O-stars in this cluster, whose winds and/or ionizing radiation may be an important factor in the removal of discs in other clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/376/144
- Title:
- BV(RI)_C_H{alpha} photometry of NGC 663
- Short Name:
- J/A+A/376/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new BV(RI)_C_H{alpha} photometry of the young open cluster NGC 663. The H{alpha} photometry is complete down to magnitude R_C_=15.4, corresponding to spectral type A5 for the cluster members. This allows detection of mild and strong H{alpha} emission in all B-type stars in the cluster. In addition to the 22 Be stars known in the observed field of NGC 663, we discovered four new faint stars of this type. We find that Be stars in NGC 663 cover the whole range of the B spectral type. They are, however, most populous among stars with spectral types falling in the range between B0 and B3, where their fraction amounts to 31+/-8%. Among B-type stars later than B3, Be stars are much less abundant: only 7 out of 101 observed stars, that is, 7+/-3%, were detected. About 70% of the observed Be stars in NGC 663 show detectable variations of light. In the time interval covered by our observations, the ranges of the largest variations reach 0.4mag in the I_C_ band. By means of the isochrone fitting, we derived the cluster distance of 2.1kpc, age of 20-25Myr, and the mean colour excess E(R-I)_C_=0.54mag, with a ~0.1mag scatter due to differential reddening.
- ID:
- ivo://CDS.VizieR/J/AJ/123/304
- Title:
- BV(RI)_C_JHK H{alpha} photometry in IC 5146
- Short Name:
- J/AJ/123/304
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The B0V star BD+46 3474 lies near the front surface of a dense molecular cloud and illuminates the emission/reflection nebula IC 5146. The HAeBe variable BD +46 3471 is embedded in the same cloud, about 10' (3.5pc) away. CCD photometry in BV(RI)_C_ (to V=22) and in JHK (to about K=16.5) has been obtained for the young clusters surrounding each of these two bright stars. Some 100 emission-H{alpha} stars brighter than R=20.5 have been found in the area, most of them in IC 5146. (Among these are two that have spectra resembling a high-excitation Herbig-Haro [HH] object plus a stellar continuum).
- ID:
- ivo://CDS.VizieR/J/AJ/132/111
- Title:
- BV(RI)_C_photometry of 77 Hyades stars
- Short Name:
- J/AJ/132/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New BV(RI)C observations of 77 stars in the Hyades are reported and discussed. The new observations are used to test published magnitudes and color indices for that cluster. For values of (V-R)C and (R-I)C published previously by Taylor & Joner (1985AJ.....90..479T and 2005, Cat. <J/ApJS/159/100>), the tests reveal no detectable scale-factor problems. In addition, the tests show that possible zero-point corrections to the published data can be no larger than a few millimagnitudes. These test results indicate that future studies requiring precision photometry for Hyades stars would be well served by selecting data samples from sources as close as possible to the native Cousins system. Tests of B-V photometry published by Johnson & Knuckles (1955ApJ...122..209J) reveal a zero-point ambiguity of approximately 8mmag in the new data that will require further measurements to resolve.
- ID:
- ivo://CDS.VizieR/J/MNRAS/384/1675
- Title:
- BVRIc photometry of Stock 8
- Short Name:
- J/MNRAS/384/1675
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVIc CCD photometry of the young open cluster Stock 8 with the aim of studying its basic properties such as the amount of interstellar extinction, distance, age, stellar contents and initial mass function (IMF). We also studied the star formation scenario in this region. From optical data, the radius of the cluster is found to be ~6arcmin (~3.6pc) and the reddening within the cluster region varies from E(B-V)=0.40 to 0.60mag. The cluster is located at a distance of 2.05+/-0.10kpc. Using H{alpha} slitless spectroscopy and Two Micron All Sky Survey (2MASS) near-infrared (NIR) data we identified H{alpha} emission and NIR-excess young stellar objects (YSOs), respectively.
- ID:
- ivo://CDS.VizieR/J/AJ/141/115
- Title:
- BV(RI)c photometry on NGC 3532
- Short Name:
- J/AJ/141/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a deep, wide-field CCD survey for the open cluster NGC 3532. Our new BV(RI)c photometry effectively covers a one square degree area and reaches an unprecedented depth of V~21 to reveal that NGC 3532 is a rich open cluster that harbors a large number of faint, low-mass stars. We employ a number of methods to reduce the impact of field star contamination in the cluster color-magnitude diagrams (CMDs), including supplementing our photometry with JHKs data from the 2MASS catalog. These efforts allow us to define a robust sample of candidate main-sequence stars suitable for a purely empirical determination of the cluster's parameters by comparing them to the well-established Hyades main sequence.
- ID:
- ivo://CDS.VizieR/J/A+A/384/890
- Title:
- BVRIHalpha photometry of NGC 2244 X-ray stars
- Short Name:
- J/A+A/384/890
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high spatial resolution optical photometry of NGC 2244 in the Rosette Nebula using the NOAO MOSAIC Imager at Kitt Peak. We obtained BVIR and H{alpha} images of the central cluster and surrounding nebulae, and present results for 138 sources selected from X-ray observations with the ROSAT PSPC and HRI. Color-magnitude diagrams of the cluster show a large number of the stars are still undergoing contraction onto the main sequence. The faintest X-ray selected cluster members have the highest X-ray-to-optical luminosities (L_x_~>7x10^30^erg/s; L_x_/L_bol_=~10^-2^ to 10^-3^) and indicate they are a population of young active late-type stars. H{alpha} emission from the X-ray emitters is also remarkable. We have extended the detections of PMS stars in NGC 2244 well into the ran ge of K spectral types. While most of the cluster stars are located in the color-magnitude diagrams in between the ZAMS and the 3Myrs isochrone, significantly younger low mass stars exist and confirm earlier reports that star formation is still going on in the Rosette Nebula/NGC 2244 region.
- ID:
- ivo://CDS.VizieR/J/AJ/128/2316
- Title:
- BVRIJHKs photometry in sigma Ori cluster
- Short Name:
- J/AJ/128/2316
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report an optical photometric survey of 0.89deg^2^ of the Orion OB1b association centered on sigma Ori. This region includes most of the sigma Ori cluster, the highest-density region within Orion OB1b. We have developed a statistical procedure to identify the young, low-mass, pre-main-sequence population of the association. We estimate that the cluster has 160 members in the mass range (0.2M_{sun}_<=M<=1.0M_{sun}_). The cluster has a radius of 35pc and an estimated age of 2.5+/-0.3Myr. We estimate that the total mass of the cluster is 225+/-30M_{sun}_. This mass is similar to the estimated mass of the ~5x10^5^yr old cluster NGC 2024. NGC 2024 and sigma Ori appear to be a well-matched pair of clusters, except for the ~2Myr difference in their ages.
- ID:
- ivo://CDS.VizieR/J/AJ/133/2696
- Title:
- BVRI light curves of Westerlund 1 stars
- Short Name:
- J/AJ/133/2696
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the first optical variability study of the Westerlund 1 super star cluster in search of massive eclipsing binary systems. A total of 129 new variable stars have been identified, including the discovery of 4 eclipsing binaries that are cluster members, 1 additional candidate, 8 field binaries, 19 field delta Scuti stars, 3 field W UMa eclipsing binaries, 13 other periodic variables, and 81 long-period or nonperiodic variables. These include the known luminous blue variable, the B[e] star, 11 Wolf-Rayet stars, several supergiants, and other reddened stars that are likely members of Westerlund 1. The bright X-ray source corresponding to the Wolf-Rayet star WR 77o (B) is found to be a 3.51 day eclipsing binary. The discovery of a reddened detached eclipsing binary system implies the first identification of main-sequence stars in Westerlund 1.
- ID:
- ivo://CDS.VizieR/J/A+A/345/521
- Title:
- BVRI photometry of NGC 2264
- Short Name:
- J/A+A/345/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The pre-main-sequence (PMS) population in the mass range between =~0.2 and =~3M_{sun}_ in southern part of the star-forming region NGC 2264 has been studied, determining both the Initial Mass Function in the region as well as the star-formation rates for different mass ranges. The sample is a composite one, derived through the union of samples obtained through different techniques and each suffering from different biases: previously known PMS stars in the region from the literature, photometrically-selected T Tauri candidates (from our own photometric data, discussed in detail in the present paper) and X-ray selected PMS candidates (discussed in detail in a companion paper) have been joined to form a sample which we show to be statistically complete (i.e. free from the biases which affect each of the parent samples) down to =~0.6M_{sun}_ (while being incomplete at lower masses). Individual masses and ages have been derived by placing the individual stars on evolutionary tracks, allowing us to derive both the IMF and the star formation rate. The Initial Mass Function thus derived for NGC 2264 shows evidence for a bimodal distribution of masses, with a break in the IMF at around 1M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AN/326/3
- Title:
- BVRI photometry of 4 open clusters
- Short Name:
- J/AN/326/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry of the galactic open clusters NGC 2627, NGC 5617, Pismis 7, and Ruprecht 75 is presented. For the first cluster, BV data are given, for the others the data are BV(RI)_c. The star coordinates are relative to the corresponding cluster center. The observations were carried out from the Complejo Astronomico El Leoncito (Argentina), and from Las Campanas (Chile). Each cluster was observed on two different nights; when possible, measurements for a given star were averaged. NGC 2627 observations were carried out from CASLEO on the nights of 7-8 January 1997 and 23-24 April 2001, in the BV filters. NGC 5617 data in the BVRI filters were obtained at Las Campanas on the nights 10-11 and 11-12 April 1996, and at CASLEO on the 1-2 April 2001 night. Pismis 7 was observed from Campanas on the 13-14 and 15-16 April 1996 nights (BVRI). Ruprecht 75 data in the BVRI filters were obtained at Las Campanas on the 12-13 April 1996 night, and at CASLEO on the 20-21 April 2001 night.
- ID:
- ivo://CDS.VizieR/J/PASP/114/1382
- Title:
- BVRI photometry of Stock 1 stars
- Short Name:
- J/PASP/114/1382
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BVRI photometry and J2000.0 positions have been obtained for stars in the field of the open cluster Stock 1. The photometry has been combined with available spectral types and proper motions to investigate cluster membership. We conclude that Stock 1 is a young cluster with a reddening of E(B-V)=0.16+/-0.04, a distance modulus of V_0_-M_V_=7.5+/-0.1, and an age of 300+/-50Myr.
- ID:
- ivo://CDS.VizieR/J/A+A/454/179
- Title:
- BVR phot. of Basel 11b, King 14, Czernik 43
- Short Name:
- J/A+A/454/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To progress in galactic studies based on open clusters, e.g. cluster formation rate or kinematical properties, one needs to improve the number of open clusters observed. However, only half of the 1700 known galactic open clusters have been properly observed so far, making any statistical investigation insignificant, especially at larger distances from the Sun. We study marginally investigated or neglected open clusters with Bessell CCD BVR photometry, whose data were used to fit isochrones to the individual color-magnitude diagrams. We examined the galactic clusters Basel 11b, King 14 and Czernik 43, the last being observed for the first time to this extent. As well as a careful comparison to available photometry, their parameters such as age, interstellar reddening, distance and apparent diameter were determined. The obtained cluster properties were verified by near infrared 2MASS data. The three investigated intermediate age clusters are all located in the galactic disk with distances between 1.8 and 3.0kpc from the Sun.
- ID:
- ivo://CDS.VizieR/J/BaltA/16/327
- Title:
- Camelopardalis dust and molecular clouds
- Short Name:
- J/BaltA/16/327
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using infrared photometric data extracted from the 2MASS, IRAS and MSX databases, 142 suspected young stellar objects (YSOs) are selected from about 2 million stars in the Camelopardalis segment of the Milky Way limited by Galactic coordinates, b=132-158{deg},+/-12{deg}.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/61
- Title:
- Candidate X-ray OB stars in MYStIX regions
- Short Name:
- J/ApJ/838/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive O-type and early B-type (OB) stars in the nearby Galaxy remain incompletely cataloged due to high extinction, bright visible and infrared nebular emission in H II regions, and high field star contamination. These difficulties are alleviated by restricting the search to stars with X-ray emission. Using the X-ray point sources from the Massive Young Star-forming Complex Study in Infrared and X-Rays (MYStIX) survey of OB-dominated regions, we identify 98 MYStIX candidate OB (MOBc) stars by fitting their 1-8{mu}m spectral energy distributions (SEDs) with reddened stellar atmosphere models. We identify 27 additional MOBc stars based on JHK_S_ photometry of X-ray stars lacking SED fitting. These candidate OB stars indicate that the current census of stars earlier than B1, taken across the 18 MYStIX regions studied, is less than 50% complete. We also fit the SEDs of 239 previously published OB stars to measure interstellar extinction and bolometric luminosities, revealing six candidate massive binary systems and five candidate O-type (super)giants. As expected, candidate OB stars have systematically higher extinction than previously published OB stars. Notable results for individual regions include identification of the OB population of a recently discovered massive cluster in NGC 6357, an older OB association in the M17 complex, and new massive luminous O stars near the Trifid Nebula. In several relatively poorly studied regions (RCW 38, NGC 6334, NGC 6357, Trifid, and NGC 3576), the OB populations may increase by factors of 2.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A28
- Title:
- Catalog of super star clusters in IRAS 17138-1017
- Short Name:
- J/A+A/639/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Currently, the global characteristics and evolution of super star clusters (SSCs) are not well understood, due to the large distances to their host galaxies. We aim to study the population of SSCs in IRAS 17138-1017, a luminous infrared galaxy (LIRG), in terms of age, extinction, mass, and luminosity distribution. We analyzed imaging data in the near-infrared from the GeMS/GSAOI instrument on the Gemini telescope and generated simulations with the radiative transfer code MontAGN. The extraction of SSCs from the images and their photometry in J, H, and Ks allowed us to derive color-color and color-magnitude diagrams. Comparison with a theoretical stellar evolutionary track gives a first hint into the extinction towards each SSC, as well as their ages, despite some degeneracy between those two quantities. Spectra given by our radiative transfer code MontAGN, which includes dust emission, also provide insightful predictions and comparisons. We detect with a fair degree of confidence 54 SSCs of m_Ks between 16 mag and 21 mag with a median instrumental uncertainty of 0.05 mag. When plotted on a color-color diagram and a color-magnitude diagram, it appears that most of the sources are very much extinct with respect to an intrinsic theoretical evolutionary track. Once de-reddened, the colors point unambiguously to two distinct and very recent starburst episodes at 2.8 and 4.5Myr. While the SSCs in the 4.5Myr starburst are distributed along the spiral arms, the 2.8Myr SSCs are concentrated in the central region. The luminosity and mass functions present a classical power-law behavior, although with shallower slopes than generally observed in LIRGs. Comparison with radiative transfer simulations shows that, especially for the youngest SSCs, the thermal emission by dust is not negligible and could explain the few very red SSCs that could not be de-reddened safely. This effect could lead to a misevaluation of the age of the starburst by at most 1 or 2Myr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/417/L6
- Title:
- Catalogue of stellar cluster properties in M83
- Short Name:
- J/MNRAS/417/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the stellar cluster population in two adjacent fields in the nearby, face-on spiral galaxy, M83, using multi-wavelength WFC3/HST imaging. After automatic detection procedures, the clusters are selected through visual inspection to be centrally concentrated, symmetric, and resolved on the images, which allows us to differentiate between clusters and likely unbound associations. We compare our sample with previous studies and show that the differences between the catalogues are largely due to the inclusion of large numbers of diffuse associations within previous catalogues as well as the inclusion of the central starburst region, where the completeness limit is significantly worse than in the surrounding regions. We derive the size distribution of the clusters, which is well described by a log-normal distribution with a peak at ~2.5pc, and find evidence for an expansion in the half-light radius of clusters with age. The luminosity function of the clusters is well approximated by a power-law with index, -2, over most of the observed range, however a steepening is seen at M_V=-9.3 and -8.8 in the inner and outer fields, respectively. Additionally, we show that the cluster population is inconsistent with a pure power-law mass distribution, but instead exhibits a truncation at the high mass end. If described as a Schechter function, the characteristic mass is 1.6 and 0.5x10^5^M_{sun}_, for the inner and outer fields, respectively, in agreement with previous estimates of other cluster populations in spiral galaxies. Comparing the predictions of the mass independent disruption (MID) and mass dependent disruption (MDD) scenarios with the observed distributions, we find that both models can accurately fit the data. However, for the MID case, the fraction of clusters destroyed (or mass lost) per decade in age is dependent on the environment, hence, the age/mass distributions of clusters are not universal. In the MDD case, the disruption timescale scales with galactocentric distance (being longer in the outer regions of the galaxy) in agreement with analytic and numerical predictions. Finally, we discuss the implications of our results on other extragalactic surveys, focussing on the fraction of stars that form in clusters and the need (or lack thereof) for infant mortality.
- ID:
- ivo://CDS.VizieR/J/MNRAS/365/110
- Title:
- CCD BVI photometry of 3 open clusters
- Short Name:
- J/MNRAS/365/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BVI photometry for poorly known southern hemisphere open clusters: NGC 2425, Haffner 10 and Czernik 29. We have calculated the density profile and established the number of stars in each cluster. The colour-magnitude diagrams of the objects show a well-defined main sequence. However, the red giant clump is present only in NGC 2425 and Haffner 10. For these two clusters we estimated the age as 2.5+/-0.5Gyr assuming metallicity of Z=0.008. The apparent distance moduli are in the ranges 13.2<(m-M)_V<13.6 and 14.3<(m-M)_V<14.7, while heliocentric distances are estimated to be 2.9<d<3.8kpc and 3.1<d<4.3kpc, respectively for NGC 2425 and Haffner 10. The angular separation of 2.4deg (150pc at mean distance) may indicate a common origin of the two clusters.
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/39.39
- Title:
- CCD Photometry of NGC 2658, 2849, 3247
- Short Name:
- J/other/RMxAA/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry of the galactic open clusters NGC 2658, NGC 2849, and NGC 3247 is presented. For the first two clusters, BV(RI)_c data are given, and for NGC 3247 the data are BV(I)_c. The observations were carried out from the Complejo Astronomico El Leoncito (Argentina), and from Las Campanas (Chile). Each cluster was observed on two different nights; when possible, measurements for a given star were averaged. NGC 2658 observations were carried out from CASLEO on the nights of 8-9 January 1997 and 18-19 April 2001, in the BVRI filters. NGC 2849 data in the BVRI filters were obtained at Las Campanas on the night 10-11 April 1996, and at CASLEO on 19-20 April 2001. NGC 3247 was observed at CASLEO on the nights 16-17 January 1996 (BV) and 1-2 April 1998 (BVI). The given star coordinates are relative to the corresponding cluster center.
- ID:
- ivo://CDS.VizieR/J/AJ/106/181
- Title:
- CCD photometry of open cluster M67
- Short Name:
- J/AJ/106/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a CCD photometric survey of the central one-half degree of the old open cluster, M67, in U, B, V, and I colors to magnitude V=20. Extensive comparison of our photometry with other published datasets shows excellent agreement, indicating that CCD photometry is capable of producing a uniform set of measurements consistent with the photometric system defined primarily by the Landolt standard sequence. The color-magnitude diagram of the cluster shows a well-defined main sequence extending at least to the limit of the photometry at M(V)=10.55 and a substantial binary sequence. At least 38 percent of cluster stars are binaries. The observations were performed on 3 nights on 15-18 February 1990 with the 1.09m telescope at Kitt Peak National Observatory with a Tektronix 512^2^ CCD camera; a standard KPNO UBVRI filter set was used, with BVR filters being the Harris et, and I the "nearly Mould" filter.
- ID:
- ivo://CDS.VizieR/J/A+A/376/745
- Title:
- CCD standards for U and I in NGC 7790
- Short Name:
- J/A+A/376/745
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric U and I standard sequences in the field of the open cluster NGC 7790 are presented. The intention is to achieve wide ranges in magnitude and colour, making these sequences suitable for calibrating deep CCD photometry. The 84 standard stars extend the BVR sequences of Odewahn et al. (1992PASP..104..553O) to the near UV and IR, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/432/491
- Title:
- CCD UBVIc photometry of Pismis 8 and Pismis 13
- Short Name:
- J/A+A/432/491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD UBVIc imaging photometry was carried out in the fields of the open clusters Pismis 8 and Pismis 13, located in the Vela-Puppis region in our Galaxy. MK spectral types have also been determined for a number of stars located in the fields of these two clusters which were used to secure membership among the brightest stars. Since our photometry goes to a fainter limit than previous studies we could provide better reddening, distance and age determinations. Both clusters are located close to the edge of the local arm in the third quadrant. Pismis 8 is a cluster about 5-7My old located at 2000pc from the Sun, while Pismis 13 was found at 2750pc with a probable age of about 100My. The estimate of the slopes of the mass functions in both cases yielded x=1.7 and x=2.1 for Pismis 8 and 13 respectively.
- ID:
- ivo://CDS.VizieR/J/other/NewA/12.461
- Title:
- CCD UBVIc photometry of Ruprecht 58
- Short Name:
- J/other/NewA/12.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a study that combines UBVI photometry, MK spectral classification and proper motions in the area of the, up to now unknown, open cluster Ruprecht 58 at the Puppis region.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1014
- Title:
- CCD UBVRIHa photometry in NGC 3603
- Short Name:
- J/AJ/127/1014
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVRI and H{alpha} photometry of the extremely compact, starburst cluster NGC 3603. Ground-based images, Hubble Space Telescope (HST) archival data, as well as Chandra X-ray data have been used for this study. We present, for the first time, optical color-magnitude diagrams (CMDs) for the stars in the cluster core down to V=22mag. A well-defined main sequence (MS) as well as low-mass pre-main-sequence (PMS) stars can clearly be seen in the CMDs. This result confirms the finding by Eisenhauer et al. (1998ApJ...498..278E) that low-mass stars are forming in the starburst cluster. We also derive an age (1+/-1Myr) and distance of the cluster (V_0_-M_V_=14.2+/-0.2mag, i.e., d=6.9+/-0.6kpc).
- ID:
- ivo://CDS.VizieR/J/A+AS/122/9
- Title:
- CCD UBVRI Photometry of 4 open clusters
- Short Name:
- J/A+AS/122/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD observations in the U, B, V, R and I passbands have been used to generate colour-colour and deep colour-magnitude diagrams for the young open star clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087. The sample consists of about 2000 stars reaching down to V=20mag. The interstellar extinction across the face of the imaged cluster regions seems to be uniform with average values of E(B-V)=0.31, 0.34 and 0.22mag for NGC 4103, NGC 5662 and NGC 6087 respectively. The distances to the clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087 have been estimated as 0.5+/-0.05, 2.0+/-0.3, 0.8+/-0.1 and 1.0+/-0.1kpc respectively, while the corresponding ages estimated from the theoretical stellar evolutionary isochrones fitted to the bright proper motion cluster members are ~100, 30, 80 and 65Myr respectively. Present data are consistent with the membership of the Cepheid variable V Cen to NGC 5662 and of S Norm to NGC 6087. Heavy contamination by foreground and background field stars has unfortunately made it impossible to reach definite conclusions about the faint luminosity function, and the data do not reach faint enough limits to investigate pre-main sequence stars.
- ID:
- ivo://CDS.VizieR/J/other/BASI/32.295
- Title:
- CCD UBVRI photometry of 3 open clusters
- Short Name:
- J/other/BASI/32.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometric observations of three open clusters Berkeley 15 (= OCl 414), Czernik 18 (= OCl 426) and NGC 2401 (= OCl 588), obtained for the first time in UBVRI filters down to V=20mag, are presented here. They are located at distances of 1259, 955 and 3467 parsecs with their respective ages estimated as ~5x10^9^years, ~0.8 to 1x10^9^years and ~1x10^9^years. While OCl 414 and OCl 426 are in the direction of the Auriga - Perseus constellations, OCl 588 is placed in the direction of Ophiuchus constellation in our Galaxy. The clusters studied here are of intermediate and old age category.
- ID:
- ivo://CDS.VizieR/J/MNRAS/327/23
- Title:
- CCD UBVRI photometry of 7 open star clusters
- Short Name:
- J/MNRAS/327/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive cluster parameters and mass functions from new UBVRI CCD photometric observations of ~3500 stars reaching down to V~20mag for the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC 4815, Pismis 20 and NGC 6253. For NGC 3105 and Hogg 15, CCD data are presented for the first time. The observations were carried out in 1992 between February 28 and March 8, June 5 and 9, and July 9 and 12 in the Cousins U, B, V, R and I photometric bands using CCD detector at the 1.0-m Elizabeth Telescope at the South African Astronomical Observatory (SAAO), Sutherland.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3210
- Title:
- Chandra observations of h Persei
- Short Name:
- J/AJ/137/3210
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe Chandra/ACIS-I observations of the massive ~13-14Myr-old cluster, h Persei, part of the famous Double Cluster (h and {chi} Per) in Perseus. Combining the list of Chandra-detected sources with new optical/IR photometry and optical spectroscopy reveals ~165 X-ray bright stars with V<~23. Roughly 142 have optical magnitudes and colors consistent with cluster membership.
- ID:
- ivo://CDS.VizieR/J/AJ/127/2659
- Title:
- CHANDRA observations of NGC 2264
- Short Name:
- J/AJ/127/2659
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a Chandra observation of a field in NGC 2264. The observations were taken with the ACIS-I camera with an exposure time of 48.1ks. We present a catalog of 263 sources, which includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. We found 41 variable sources, 14 of which have a flarelike light curve, and two of which have a pattern of a steady increase or decrease over a 10-hr period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being premain-sequence stars with ages younger than 3Myr.
- ID:
- ivo://CDS.VizieR/J/ApJ/614/267
- Title:
- Chandra sources in Cha I North
- Short Name:
- J/ApJ/614/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sensitive X-ray imaging surveys provide a new and effective tool to establish the census of pre-main-sequence (PMS) stars in nearby young stellar clusters. We report here a deep Chandra X-Ray Observatory observation of PMS stars in the Chamaeleon I North cloud, achieving a limiting luminosity of log L_t_~27ergs/s (0.5-8keV band) in a 0.8x0.8pc^2^ region. Of the 107 X-ray sources, 37 are associated with Galactic stars of which 27 are previously recognized cloud members.
- ID:
- ivo://CDS.VizieR/J/ApJ/770/98
- Title:
- Chandra study of NGC 6791
- Short Name:
- J/ApJ/770/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first X-ray study of NGC 6791, one of the oldest open clusters known (8Gyr). Our Chandra observation is aimed at uncovering the population of close interacting binaries down to L_X_~1x10^30^erg/s (0.3-7keV). We detect 86 sources within 8' of the cluster center, including 59 inside the half-mass radius. We identify 20 sources with proper-motion cluster members, which are a mix of cataclysmic variables (CVs), active binaries (ABs), and binaries containing sub-subgiants. With follow-up optical spectroscopy, we confirm the nature of one CV. We discover one new, X-ray variable candidate CV with Balmer and He II emission lines in its optical spectrum; this is the first X-ray-selected CV in an open cluster. The number of CVs per unit mass is consistent with the field, suggesting that the 3-4 CVs observed in NGC 6791 are primordial. We compare the X-ray properties of NGC 6791 with those of a few old open (NGC 6819, M67) and globular clusters (47 Tuc, NGC 6397). It is puzzling that the number of ABs brighter than 1x10^30^erg/s normalized by cluster mass is lower in NGC 6791 than in M 67 by a factor ~3-7. CVs, ABs, and sub-subgiants brighter than 1x10^30^erg/s are under-represented per unit mass in the globular clusters compared to the oldest open clusters, and this accounts for the lower total X-ray luminosity per unit mass of the former. This indicates that the net effect of dynamical encounters may be the destruction of even some of the hardest (i.e., X-ray-emitting) binaries.
- ID:
- ivo://CDS.VizieR/J/ApJ/588/1009
- Title:
- Chandra X-ray observations of NGC 2516
- Short Name:
- J/ApJ/588/1009
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive study of the Chandra X-ray observations of the young open cluster NGC 2516. We have analyzed eight individual Chandra observations. We have combined the data to achieve the greatest sensitivity, reaching down to log f_X_=-14.56(erg/s/cm^2^), or logLX=28.69(erg/s) at the distance of NGC 2516. Out of 284 X-ray sources detected, 155 are identified with photometric cluster members, with very little ambiguity.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A156
- Title:
- Cluster formation toward Be87/ON2. I.
- Short Name:
- J/A+A/650/A156
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Disentangling line-of-sight alignments of young stellar populations is crucial for observational studies of star-forming complexes. This task is particularly problematic in a Cygnus-X subregion where several components, located at different distances, overlap: the Berkeley 87 young massive cluster, the poorly known [DB2001] Cl05 embedded cluster, and the ON2 star-forming complex, which in turn is composed of several HII regions. We provide a methodology for building an exhaustive census of young objects that can consistently treat large differences in extinction and distance. OMEGA2000 near-infrared observations of the Berkeley 87 / ON2 field were merged with archival data from Gaia, Chandra, Spitzer, and Herschel, and with cross-identifications from the literature. To address the incompleteness effects and selection biases that arise from the line-of-sight overlap, we adapted existing methods for extinction estimation and young object classification. We also defined the intrinsic reddening index, R_int_, a new tool for separating intrinsically red sources from those whose infrared color excess is caused by extinction. Finally, we introduce a new method for finding young stellar objects based on R_int_. We find 571 objects whose classification is related to recent or ongoing star formation. Together with other point sources with individual estimates of distance or extinction, we compile a catalog of 3005 objects to be used for further membership work. A new distance for Berkeley 87, (1673+/-17)pc, is estimated as a median of 13 spectroscopic members with accurate Gaia EDR3 parallaxes. The flexibility of our approach, especially regarding the R_int_ definition, allows overcoming photometric biases caused by large variations in extinction and distance, in order to obtain homogeneous catalogs of young sources. The multiwavelength census that results from applying our methods to the Berkeley 87 / ON2 field will serve as a basis for disentangling the overlapped populations.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/110
- Title:
- CN and CH indexes in stars of NGC 6791
- Short Name:
- J/ApJ/758/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Low-resolution SDSS/SEGUE spectra have been used to study the behavior of the strengths of the CN and CH molecular bands in stars at different evolutionary stages of the open cluster NGC 6791. We find a significant spread in the strengths of the CN bands, more than twice that expected from the uncertainties, although the bimodalities observed in globular clusters are not clearly observed here. This behavior is observed not only among red clump objects but also in unevolved stars such as those in the main sequence and lower red giant branch. In contrast, not all of the stars studied show significant scatter in their CH strengths.
- ID:
- ivo://CDS.VizieR/J/A+A/418/525
- Title:
- Collinder 232 & Trumpler 14/16 UBVRI photometry
- Short Name:
- J/A+A/418/525
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present and analyze new CCD UBVRI photometry down to V~21 in the region of the young open cluster Collinder 232, located in the Carina spiral arm, and discuss its relationship to Trumpler 14 and Trumpler 16, the two most prominent young open clusters located in the core of NGC 3372 (the Carina Nebula).
- ID:
- ivo://CDS.VizieR/J/A+A/526/A21
- Title:
- Collinder 69 X-ray sources
- Short Name:
- J/A+A/526/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first paper of a series devoted to the {lambda} Orionis star-forming region, Orion's Head, from the X-ray perspective. Our final aim is to provide a comprehensive view of this complex region, which includes several distinct associations and dark clouds. We aim to uncover the population of the central, young star cluster Collinder 69, and in particular those diskless Class III objects not identified by previous surveys based on near- and mid-infrared searches, and to establish the X-ray luminosity function for the association.
- ID:
- ivo://CDS.VizieR/J/AJ/136/2483
- Title:
- Comoving group associated with HD 141569
- Short Name:
- J/AJ/136/2483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for a young stellar moving group associated with the star HD 141569 - a nearby, isolated Herbig AeBe primary member of a 5+/-3Myr-old triple star system on the outskirts of the Sco-Cen complex. Our spectroscopic survey identified a population of 21 Li-rich, >~30Myr-old stars within 30{deg} of HD 141569 which possess similar proper motions with the star. The spatial distribution of these Li-rich stars, however, is not suggestive of a moving group associated with the HD 141569 triplet, but rather this sample appears cospatial with Upper Scorpius (US) and Upper Centaurus Lupus (UCL). We apply a modified moving cluster parallax method to compare the kinematics of these youthful stars with those of the US and UCL. Eight new potential members of US and five new potential members of UCL are identified. A substantial moving group with an identifiable nucleus within 15{deg} (~30pc) of HD 141569 is not found in this sample. Evidently, the HD 141569 system formed ~5Myr ago in relative isolation, tens of parsecs away from the recent sites of star formation in the Ophiucus-Scorpius-Centaurus region.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A120
- Title:
- DANCe study of M35 (NGC 2168)
- Short Name:
- J/A+A/575/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Messier 35 (NGC 2168) is an important young nearby cluster. Its age, richness and relative proximity make it a privileged target for stellar evolution studies. The Kepler K2 mission recently observed it and provided high accuracy photometric time series of a large number of sources in this area of the sky. Identifying the cluster's members is therefore of high importance to optimize the interpretation and analysis of the Kepler K2 data. We aim at identifying the cluster's members by deriving membership probabilities for the sources within 1 degree of the cluster's center, going further away than equivalent previous studies. We measure accurate proper motions and multi-wavelength (optical and near-infrared) photometry using ground based archival images of the cluster. We use these measurements to compute membership probabilities. The list of candidate members from Barrado y Navascues et al. (2001ApJ...546.1006B, Cat. J/ApJ/546/1006) is used as training set to identify the cluster's locus in a multi-dimensional space made of proper motions, luminosities and colors. The final catalog includes 338892 sources with multi-wavelength photometry. Approximately half (194452) were detected at more than two epochs and we measured their proper motion and used it to derive membership probability. A total of 4349 candidate members with membership probabilities greater than 50% are found in this sample in the luminosity range between 10 and 22mag. The slow proper motion of the cluster and the overlap of its sequence with the field and background sequences in almost all color-magnitude and color-color diagrams complicate the analysis and the contamination level is expected to be significant. Our study nevertheless provides a coherent and quantitative membership analysis of Messier 35 based on a large fraction of the best ground-based data sets obtained over the past 18 years. As such, it represents a valuable input for follow-up studies using in particular the Kepler K2 photometric time series.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A54
- Title:
- Danks 1, Danks 2, and RCW 79 variables
- Short Name:
- J/A+A/545/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ESO Public Survey "VISTA Variables in the Via Lactea"' (VVV) provides deep multi-epoch infrared observations for unprecedented 562 sq. degrees of the Galactic bulge, and adjacent regions of the disk. The VVV observations will foster the construction of a sample of Galactic star clusters with reliable and homogeneously derived physical parameters (e.g., age, distance, and mass, etc.). In this first paper in a series, the methodology employed to establish cluster parameters for the envisioned database are elaborated upon by analysing four known young open clusters: Danks1, Danks2, RCW79, and DBS132. The analysis offers a first glimpse of the information that can be gleaned from the VVV observations for clusters in the final database. Wide-field, deep JHK_s_ VVV observations, combined with new infrared spectroscopy, are employed to constrain fundamental parameters for a subset of clusters. Results are inferred from VVV near-infrared photometry and numerous low resolution spectra (typically more than 10 per cluster). The high quality of the spectra and the deep wide-field VVV photometry enables us to precisely and independently determine the characteristics of the clusters studied, which we compare to previous determinations. An anomalous reddening law in the direction of the Danks clusters is found, specifically E(J-H)/E(H-Ks)=2.20+/-0.06, which exceeds published values for the inner Galaxy. The G305 star forming complex, which includes the Danks clusters, lies beyond the Sagittarius-Carina spiral arm and occupies the Centaurus arm. Finally, the first deep infrared colour-magnitude diagram of RCW79 is presented, which reveals a sizeable pre-main sequence population. A list of candidate variable stars in G305 region is reported. This study demonstrates the strength of the dataset and methodology employed, and constitutes the first step of a broader study which shall include reliable parameters for a sizeable number of poorly characterised and/or newly discovered clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/688/597
- Title:
- Debris disks in NGC 2232
- Short Name:
- J/ApJ/688/597
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe Spitzer IRAC and MIPS observations of the nearby 25Myr old open cluster NGC 2232. Combining these data with ROSAT All-Sky Survey observations, proper motions, and optical photometry/spectroscopy, we construct a list of highly probable cluster members. We identify one A-type star, HD 45435, that has definite excess emission at 4.5-24um indicative of debris from terrestrial planet formation. We also identify 2-4 late-type stars with possible 8um excesses and 8 early-type stars with definite 24um excesses. Constraints on the dust luminosity and temperature suggest that the detected excesses are produced by debris disks. From our sample of B and A stars, stellar rotation appears to be correlated with 24um excess, a result that would be expected if massive primordial disks evolve into massive debris disks. To explore the evolution of the frequency and magnitude of debris around A-type stars, we combine our results with data for other young clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A92
- Title:
- Deep all-sky census of the Hyades
- Short Name:
- J/A+A/531/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the basis of the PPMXL catalogue we perform an all-sky census of the Hyades down to masses of about 0.2M_{sun}_ in a region up to 30pc from the cluster centre. We use the proper motions from PPMXL in the convergent point method to determine probable kinematic members. From 2MASS photometry and CMC14 r'-band photometry, we derive empirical colour-absolute magnitude diagrams and, finally, determine photometric membership for all kinematic candidates. This is the first deep (r'<17) all-sky survey of the Hyades allowing a full three-dimensional analysis of the cluster. The survey is complete down to at least M_{K_s_}_=7.3 or 0.25M_{sun}_. We find 724 stellar systems co-moving with the bulk Hyades space velocity, which represent a total mass of 435M_{sun}_. The tidal radius is about 9pc, and 275M_{sun}_ (364 systems) are gravitationally bound. This is the cluster proper. Its mass density profile is perfectly fitted by a Plummer model with a central density of 2.21M_{sun}_/pc^3^ and a core radius of r_co_=3.10pc, while the half-mass radius is r_h_=4.1pc. There are another 100M_{sun}_ in a volume between one and two tidal radii (halo), and another 60M_{sun}_ up to a distance of 30pc from the centre. Strong mass segregation is inherent in the cluster. The present-day luminosity and mass functions are noticeably different in various parts of the cluster (core, corona, halo, and co-movers). They are strongly evolved compared to presently favoured initial mass functions. The analysis of the velocity dispersion of the cluster shows that about 20% of its members must be binaries. As a by-product, we find that presently available theoretical isochrones are not able to adequately describe the near-infrared colour-absolute magnitude relation for those cluster stars that are less massive than about 0.6M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AJ/138/703
- Title:
- Deep MIPS observations of IC 348 nebula
- Short Name:
- J/AJ/138/703
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe new, deep MIPS photometry and new high signal-to-noise optical spectroscopy of the 2.5Myr old IC 348 Nebula. To probe the properties of the IC 348 disk population, we combine these data with previous optical/infrared photometry and spectroscopy to identify stars with gas accretion, to examine their mid-IR colors, and to model their spectral energy distributions.
- ID:
- ivo://CDS.VizieR/J/A+A/324/549
- Title:
- Deep UVBRI photometry in IC 348
- Short Name:
- J/A+A/324/549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table3 contains UBVRI-CCD photometry for the 123 observed stars in the nucleus of IC 348 open cluster. Magnitude and colours are given with their corresponding errors. Column "N" gives the number of observations. Spectral types and cross-identifications with other catalogues are given in note file. Table5 contains adopted reddening solution for the brightest members in IC 348
- ID:
- ivo://CDS.VizieR/J/A+A/650/A157
- Title:
- Dolidze 25 Chandra/ACIS-I X-ray sources
- Short Name:
- J/A+A/650/A157
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The dispersal of protoplanetary disks sets the timescale available for planets to assemble, and thus it is one of the fundamental parameters in theories of planetary formation. Disk dispersal is determined by several properties of the central star, the disk itself, and the surrounding environment. In particular, the metallicity of disks may impact their evolution, even if to date controversial results exist: in low-metallicity clusters disks seem to rapidly disperse, while in the Magellanic Clouds some evidence supports the existence of accreting disks few tens of Myrs old. In this paper we study the dispersal timescale of disks in Dolidze 25, the young cluster in proximity of the Sun with lowest metallicity, with the aim of understanding whether disk evolution is impacted by the low-metallicity of the cluster. We have analyzed Chandra/ACIS-I observations of the cluster and combined the resulting source catalog with existing optical and infrared catalogs of the region. We selected the disk-bearing population in a 1 degree circular region centered on Dolidze~25 from criteria based on infrared colors, and the disk-less population within a smaller central region among the X-ray sources with OIR counterpart. In both cases, criteria are applied to discard contaminating sources in the foreground/background. We have derived stellar parameters from isochrones fitted to color-magnitude diagrams. We derived a disk fraction of about 34% and a median age of the cluster of 1.2Myrs. To minimize the impact of incompleteness and spatial inhomogeneity of the list of members, we restricted this calculation to stars in a magnitude range where our selection of cluster members is fairly complete and by adopting different cuts in stellar masses. By comparing this estimate with existing estimates of the disk fraction of clusters younger than 10Myrs, our study suggests that the disk fraction of Dolidze 25 is lower than what is expected from its age alone. Even if our results are not conclusive given the intrinsic uncertainty on stellar ages estimated from isochrones fitting to color-magnitude diagrams, we suggest that disk evolution in Dolidze 25 may be impacted by the environment. Given the poor O star population and low stellar density of the cluster, it is more likely that disks dispersal timescale is dictated more by the low metallicity of the cluster rather than external photoevaporation or dynamical encounters.
- ID:
- ivo://CDS.VizieR/J/AJ/158/82
- Title:
- DS Andromedae radial velocity & photometric data
- Short Name:
- J/AJ/158/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Wilson-Devinney program has been used to analyze well-calibrated photometric and new radial velocity data to determine the properties and distance of DS Andromedae, a 1.01 day period, double-lined, totally eclipsing binary system of early-F spectral type and a likely member of the intermediate-age open cluster NGC 752. The determinations of many of the system elements including the distance are robust against modest changes in model assumptions. Third light is present in all passbands at the 10% level. The weighted means of the best-fitting model yield a distance of 477+/-4+/-12 pc, equivalent to (m-M)_0_=8.390+/-0.018+/-0.060 mag, and masses of 1.655+/-0.003+/-0.030 M_Sun_ and 1.087+/-0.005+/-0.040 M_Sun_, radii of 2.086+/-0.003+/-0.013 and 1.255+/-0.005+/-0.012 R_Sun_, and effective temperatures 7056+/-21+/-140 R_Sun_ and 5971+/-33+/-130 K, for components 1 and 2, respectively, where the formal internal uncertainties are followed by conservatively estimated systematic errors. Possible but less satisfactory semidetached models produce more parameter variations and larger mean residuals. The primary star is seen to be at or very close to the main-sequence turnoff at an age of 1.55+/-0.05 Gyr but appears to be too small for its mass, whereas the secondary appears to be too luminous for its temperature and too large for its mass compared to models of single stars.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A8
- Title:
- Evolved Galactic open clusters dynamical properties
- Short Name:
- J/A+A/624/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar content of Galactic open clusters (OCs) is gradually depleted during their evolution as a result of internal relaxation and external interactions. The final residues of the long-term evolution of OCs are called open cluster remnants (OCRs).These are sparsely populated structures that can barely be distinguished from the field. We aimed to characterise and compare the dynamical states of a set of 16 objects catalogued as OCRs or OCR candidates. The sample also includes 7 objects that are catalogued as dynamically evolved OCs for comparison purposes. We used photometric data from the 2MASS catalogue, proper motions and parallaxes from the GAIA DR2 catalogue, and a decontamination algorithm that was applied to the three-dimensional astrometric space of proper motions and parallaxes ({mu}_{alpha}, {mu}_{delta}, {varpi}) for stars in the objects' areas. The investigated OCRs present masses (M) and velocity dispersions ({sigma}_v_) within well-defined ranges: M between ~10-40M_{sun} and {sigma}_v_ between ~1-7km/s. Some objects in the remnant sample have a limiting radius R_lim_<~2pc, which means that they are more compact than the investigated OCs; other remnants have R_lim_ between ~2-7pc, which is comparable to the OCs. In general, our clusters show signals of depletion of low-mass stars. This confirms their dynamically evolved states. Using results from N-body simulations, we conclude that the OCRs we studied are in fact remnants of initially very populous OCs (N_0_~10^3^-10^4^stars). The outcome of the long-term evolution is to bring the final residues of the OCs to dynamical states that are similar to each other, thus masking out the memory of the initial formation conditions of star clusters.
- ID:
- ivo://CDS.VizieR/V/137D
- Title:
- Extended Hipparcos Compilation (XHIP)
- Short Name:
- V/137D
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Extended Hipparcos Compilation (XHIP) cross-references the New Hipparcos Reduction (HIP2, Cat. I/311) with relatable data from a broad survey of presently available sources. The resulting collection uniquely assigns 116,096 spectral classifications, 46,392 radial velocities, and 19,097 iron abundances [Fe/H] to Hipparcos stars. Stellar classifications from SIMBAD and indications of multiplicity from either CCDM (Cat. I/274) or WDS (Cat. B/wds) are provided. Parameters for solar encounters and Galactic orbits are calculated for a subset of stars that can be made kinematically complete. Memberships in open clusters and stellar associations are assigned. We also provide stellar ages from The Geneva-Copenhagen survey of the Solar neighbourhood III (Cat. V/130), identifications of exoplanet host stars, and supplemental photometry from 2MASS (Cat. II/246) and SIMBAD.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/113
- Title:
- Extinction law in the Cep OB3b young cluster
- Short Name:
- J/ApJ/786/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine the extinction law through Cep OB3b, a young cluster of 3000 stars undergoing gas dispersal. The extinction is measured toward 76 background K giants identified with MMT/Hectospec spectra. Color excess ratios were determined toward each of the giants using V and R photometry from the literature, g, r, i, and z photometry from the Sloan Digital Sky Survey and J, H, and K_s_ photometry from the Two Micron All Sky Survey. These color excess ratios were then used to construct the extinction law through the dusty material associated with Cep OB3b. The extinction law through Cep OB3b is intermediate between the R_V_=3.1 and R_V_=5 laws commonly used for the diffuse atomic interstellar medium and dense molecular clouds, respectively. The dependence of the extinction law on line-of-sight A_V_ is investigated and we find the extinction law becomes shallower for regions with A_V_>2.5 mag. We speculate that the intermediate dust law results from dust processing during the dispersal of the molecular cloud by the cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/649/L8
- Title:
- Extreme adaptive optics astrometry of R136
- Short Name:
- J/A+A/649/L8
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We compared high-contrast near-infrared images of the core of R136 taken by VLT/SPHERE, in two epochs separated by 3.06 years. For the first time we monitored the dynamics of the detected sources in the core of R136 from a ground-based telescope with adaptive optics. The aim of these observations was to search for High prOper Motion cAndidates (HOMAs) in the central region of R136 (r<6") where it has been challenging for other instruments. Two bright sources (K<15mag and V<16mag) are located near R136a1 and R136c (massive WR stars) and have been identified as potential HOMAs. These sources have significantly shifted in the images with respect to the mean shift of all reliable detected sources and their neighbours, and six times their own astrometric errors. We calculate their proper motions to be 1.36+/-0.22mas/yr^2^ (321+/-52km/s) and 1.15+/-0.11mas/yr^2^ (273+/-26km/s). We discuss different possible scenarios to explain the magnitude of such extreme proper motions, and argue for the necessity to conduct future observations to conclude on the nature of HOMAs in the core of R136.