- ID:
- ivo://CDS.VizieR/J/A+A/640/A128
- Title:
- Cygnus OB2 association NIR light curves
- Short Name:
- J/A+A/640/A128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a J, H, and K photometric variability survey of the central 0.78 square degrees of the young OB association Cygnus OB2. We used data observed with the Wide-Field CAMera at the United Kingdom Infrared Telescope in 2007 (spanning 217 days) to investigate the light curves of 5083 low mass candidate members in the association and explore the occurrence and main characteristics of their near-infrared variability. We identified 2529 stars (~50% of the sample) with significant variability with time-scales ranging from days to months. We classified the variable stars into the following three groups according to their light curve morphology: periodic variability (1697 stars), occultation variability (124 stars), and other types of variability (726 stars). We verified that the disk-bearing stars in our sample are significantly more variable in the near-infrared than diskless stars, with a steep increase in the disk-fraction among stars with higher variability amplitude. We investigated the trajectories described by variable stars in the color-space and measured slopes for 335 stars describing linear trajectories. Based on the trajectories in the color-space, we inferred that the sample analyzed is composed of a mix of young stars presenting variability due to hot and cold spots, extinction by circumstellar material, and changes in the disk emission in the near-infrared. We contemplated using the use of near- infrared variability to identify disk-bearing stars and verified that 53.4% of the known disk-bearing stars in our sample could have been identified as such based solely on their variability. We present 18 newly identified disk- bearing stars and 14 eclipsing binary candidates among CygOB2 lower-mass members.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/705/1646
- Title:
- Debris disks in Upper Sco
- Short Name:
- J/ApJ/705/1646
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present MIPS 24um and 70um photometry for 205 members of the Upper Scorpius OB Association. These data are combined with published MIPS photometry for 15 additional association members to assess the frequency of circumstellar disks around 5Myr old stars with spectral types between B0 and M5. Twelve stars have a detectable 70um excess, each of which also has a detectable 24um excess. A total of 54 stars are identified with a 24um excess more than 32% above the stellar photosphere. The MIPS observations reveal 19 excess sources - 8 A/F/G stars and 11 K/M stars - that were not previously identified with an 8um or 16um excess. The lack of short-wavelength emission and the weak 24um excess suggests that these sources are debris systems or the remnants of optically thick primordial disks with inner holes. Despite the wide range of luminosities of the stars hosting apparent debris systems, the excess characteristics are consistent with all stars having dust at similar orbital radii after factoring in variations in the radiation blowout particle size with spectral type. The results for Upper Sco are compared to similar photometric surveys from the literature to re-evaluate the evolution of debris emission.
- 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/ApJ/688/362
- Title:
- Disks around brown dwarfs in {sigma} Ori cluster
- Short Name:
- J/ApJ/688/362
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a census of circumstellar disks around brown dwarfs in the {sigma} Ori cluster using all available images from the Infrared Array Camera on board the Spitzer Space Telescope. To search for new low-mass cluster members with disks, we have measured photometry for all sources in the Spitzer images and have identified the ones that have red colors that are indicative of disks. We present five promising candidates, which may consist of two brown dwarfs, two stars with edge-on disks, and a low-mass protostar if they are bona fide members. Spectroscopy is needed to verify the nature of these sources. We have also used the Spitzer data to determine which of the previously known probable members of {sigma} Ori are likely to have disks. By doing so, we measure disk fractions of ~40% and ~60% for low-mass stars and brown dwarfs, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A67
- Title:
- Embedded YSOs in Carina Nebula complex
- Short Name:
- J/A+A/549/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Carina Nebula represents one of the largest and most active star forming regions known in our Galaxy. It contains numerous very massive (M>~40M_{sun}) stars that strongly act the surrounding clouds by their ionizing radiation and stellar winds. Our recently obtained Herschel PACS & SPIRE far-infrared maps cover the full area (~~8.7{deg}^2^) of the Carina Nebula complex and reveal the population of deeply embedded young stellar objects, most of which are not yet visible in the mid- or near-infrared. We study the properties of the 642 objects that are independently detected as point-like sources in at least two of the five Herschel bands. For those objects that can be identified with apparently single Spitzer counterparts, we use radiative transfer models to derive information about the basic stellar and circumstellar parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/161/87
- Title:
- Gaia data for members of {epsilon}Cha
- Short Name:
- J/AJ/161/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The precise parallax, proper motion, and photometric measurements contained in Gaia Data Release 2 (DR2) offer the opportunity to reexamine the membership and ages of nearby young moving groups (NYMGs), i.e., loose groups of stars of age <~100Myr in the solar vicinity. Here, we analyze the available DR2 data for members and candidate members of the {epsilon}Cha Association ({epsilon}CA) which, at an estimated age of ~3-5Myr, has previously been identified as among the youngest NYMGs. The several dozen confirmed members of {epsilon}CA include MPMus and TCha, two of the nearest stars of roughly solar mass that are known to host primordial protoplanetary disks, and the Herbig Ae/Be star HD104237A. We have used Gaia DR2 data to ascertain the Galactic positions and kinematics and color-magnitude diagram positions of {epsilon}CA members and candidates so as to reassess their membership status and thereby refine estimates of the distance, age, multiplicity, and disk fraction of the group. Our analysis yields 36 bona fide {epsilon}CA members, as well as 20 provisional members, including 3 new members identified here as comoving companions to previously known {epsilon}CA stars. We determine a mean distance to {epsilon}CA of 101.0{+/-}4.6pc and confirm that, at an age of 5_-2_^+3^Myr, {epsilon}CA represents the youngest stellar group within ~100pc of Earth. We identify several new photometric binary candidates, bringing the overall multiplicity fraction (MF) of {epsilon}CA to 40%, intermediate between the MFs of young T associations and the field.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1117
- Title:
- Halpha emission-line stars in NGC2264
- Short Name:
- J/AJ/127/1117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep survey of H{alpha} emission-line stars in the NGC 2264 region using wide-field objective prism films. We find 357 H{alpha} emission-line stars, of which 113 were previously detected, within an area of 3{deg}x3{deg} centered on the Cone Nebula, with a majority of stars being concentrated in a dense cluster at the center of the region. We present a large-scale CO map of NGC 2264 and find a strong correlation between the cluster of H{alpha} emission-line stars and the most massive core in the cloud complex. A more extended halo of stars poorly correlated with the gas may represent stars that have drifted away from their birth place, suggesting that star formation has taken place in NGC 2264 for several million years.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1530
- Title:
- H{alpha} emission stars in LDN988
- Short Name:
- J/AJ/131/1530
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- L988 is a large (~0.5{deg}x0.7{deg}) dark cloud complex at about 600pc that contains several bright pre-main-sequence objects (such as V1331 Cyg and LkH{alpha} 321), but this paper deals in detail only with a small region on its eastern edge, near the HAeBe star LkH{alpha} 324. That star and its distant companion LkH{alpha} 324SE lie at the apex of a V-shaped area apparently excavated from the edge of L988, and are the brightest members of a small cluster containing about 50 H{alpha}-emission stars.
- ID:
- ivo://CDS.VizieR/J/A+A/613/L5
- Title:
- H{alpha} emitting sources around MWC758
- Short Name:
- J/A+A/613/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- MWC758 is a young star surrounded by a transitional disk. The disk shows an inner cavity and spiral arms that could be caused by the presence of protoplanets. Recently, a protoplanet candidate has been detected around MWC758 through high-resolution L'-band observations. The candidate is located inside the disk cavity at a separation of 111 mas from the central star, and at an average position angle of 165.5{deg}. We aim at detecting accreting protoplanet candidates within the disk of MWC758 through spectral angular differential imaging observations in the optical regime. In particular, we explore the emission at the position of the detected planet candidate. We have performed simultaneous adaptive optics observations in the H{alpha} line and the adjacent continuum using SPHERE/ZIMPOL at the Very Large Telescope (VLT). The data analysis does not reveal any H{alpha} signal around the target. The derived contrast curve in the B_Ha filter allows us to derive a 5{sigma} upper limit of 7.6mag at 111mas, the separation of the previously detected planet candidate. This contrast translates into a H{alpha} line luminosity of LH{alpha}<~5*10^-5^L_{sun}_ at 111mas. Assuming that LH{alpha} scales with Lacc as in Classical T Tauri stars as a first approximation, we can estimate an accretion luminosity of Lacc<3.7*10^-4^L_{sun}_ for the protoplanet candidate. For the predicted mass range of MWC758b, 0.5-5M_Jup_, this implies accretion rates smaller than dM/dt<3.4*(10^-8^-10^-9^)M_[sun}_/yr, for an average planet radius of 1.1 RJup. Therefore, our estimates are consistent with the predictions of accreting circumplanetary accretion models for R_in_=1R_Jup_. The ZIMPOL line luminosity is consistent with the H{alpha} upper limit predicted by these models for truncation radii <~3.2R_Jup_. The non-detection of any H{alpha}emitting source in the ZIMPOL images does not allow us to unveil the nature of the L' detected source. Either it is a protoplanet candidate or a disk asymmetry.
- ID:
- ivo://CDS.VizieR/J/AJ/143/61
- Title:
- H{alpha} spectroscopy in IC 1396 HII region
- Short Name:
- J/AJ/143/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made an extensive survey of emission-line stars in the IC 1396 H II region to investigate the low-mass population of pre-main-sequence (PMS) stars. A total of 639 H{alpha} emission-line stars were detected in an area of 4.2deg^2^ and their i' photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H II region (Rim B and SFO 37, 38, 39, 41), and near HD206267, which is the main exciting star of the HII region. Based on the extinction estimated from the near-infrared color-color diagram, we have selected PMS star candidates associated with IC1396. The age and mass were derived from the extinction-corrected color-magnitude diagram and theoretical PMS tracks. Most of our PMS candidates have ages of <3Myr and masses of 0.2-0.6M_{sun}_. Although it appears that only a few stars were formed in the last 1Myr in the east region of the exciting star, the age difference among subregions in our surveyed area is not clear from the statistical test. Our results may suggest that massive stars were born after the continuous formation of low-mass stars for 10Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud. It may have triggered the formation of many low-mass stars at the dense inhomogeneity in and around the HII region by a radiation-driven implosion.