- ID:
- ivo://CDS.VizieR/J/A+A/626/A11
- Title:
- Corona Australis ALMA and X-Shooter data
- Short Name:
- J/A+A/626/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years, the disk populations in a number of young star-forming regions have been surveyed with the Atacama Large Millimeter/submillimeter Array (ALMA). Understanding the disk properties and their correlation with the properties of the central star is critical to understanding planet formation. In particular, a decrease of the average measured disk dust mass with the age of the region has been observed, consistent with grain growth and disk dissipation. We aim to compare the general properties of disks and their host stars in the nearby (d=160pc) Corona Australis (CrA) star forming region to those of the disks and stars in other regions. We conducted high-sensitivity continuum ALMA observations of 43 Class II young stellar objects in CrA at 1.3mm (230GHz). The typical spatial resolution is 0.3''. The continuum fluxes ar e used to estimate the dust masses of the disks, and a survival analysis is performed to estimate the average dust mass. We also obtained new VLT/X-Shooter spectra for 12 of the objects in our sample for which spectral type (SpT) information was missing. Twenty-four disks were detected, and stringent limits have been put on the average dust mass of the nondetections. Taking into account the upper limits, the average disk mass in CrA is 6+/-3M_{sun}_. This value is significantly lower than that of disks in other young (1-3Myr) star forming regions (Lupus, Taurus, Chamaeleon I, and Ophiuchus) and appears to be consistent with the average disk mass of the 5-10Myr-old Upper Sco. The position of the stars in our sample on the Herzsprung-Russel diagram however seems to confirm that CrA has an age similar to Lupus. Neither external photoevaporation nor a lower-than-usual stellar mass distribution can explain the low disk masses. On the other hand, a low-mass disk population could be explained if the disks were small, which could happen if the parent cloud had a low temperature or intrinsic angular momentum, or if the angular momentum of the cloud were removed by some physical mechanism such as magnetic braking. Even in detected disks, none show clear substructures or cavities. Our results suggest that in order to fully explain and understand the dust mass distribution of protoplanetary disks and their evolution, it may also be necessary to take into consideration the initial conditions of star- and disk-formation process. These conditions at the very beginning may potentially vary from region to region, and could play a crucial role in planet formation and evolution.
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- ID:
- ivo://CDS.VizieR/J/A+A/589/A60
- Title:
- CO, SO and H_2_CO images of AB Aur
- Short Name:
- J/A+A/589/A60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transitional disks are structures of dust and gas around young stars with large inner cavities in which planet formation may occur. Lopsided dust distributions are observed in the dust continuum emission at millimeter wavelengths. These asymmetrical structures can be explained as being the result of an enhanced gas density vortex where the dust is trapped, potentially promoting the rapid growth to the planetesimal scale. AB Aur hosts a transitional disk with a clear horseshoe morphology which strongly suggests the presence of a dust trap. Our goal is to investigate its formation and the possible effects on the gas chemistry. We used the NOrthern Extended Millimeter Array (NOEMA) interferometer to image the 1mm continuum dust emission and the ^13^CO J=2->1, C^18^O J=2->1, SO J=5_6_->4_5_, and H_2_CO J=3_03_->2_02_. rotational lines.
- ID:
- ivo://CDS.VizieR/J/ApJS/160/319
- Title:
- COUP: observations and source lists
- Short Name:
- J/ApJS/160/319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a description of the data reduction methods and the derived catalog of more than 1600 X-ray point sources from the exceptionally deep 2003 January Chandra X-Ray Observatory (Chandra) observation of the Orion Nebula Cluster and embedded populations around OMC-1. The observation was obtained with Chandra's Advanced CCD Imaging Spectrometer (ACIS) and has been nicknamed the Chandra Orion Ultradeep Project (COUP). With an 838ks exposure made over a continuous period of 13.2 days, the COUP observation provides the most uniform and comprehensive data set on the X-ray emission of normal stars ever obtained in the history of X-ray astronomy.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1602
- Title:
- Cousins RI photometry in IC 348
- Short Name:
- J/AJ/127/1602
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The extremely young cluster IC 348 has been monitored photometrically over five observing seasons from 1998 December 10 to 2003 March 26 in Cousins I with a 0.6m telescope at Van Vleck Observatory. Twenty-eight periodic variables and 16 irregular variables have been identified. The variability study is most sensitive for stars with I<14.3mag; at that brightness level, we find that 24 of the 27 known pre-main-sequence (PMS) cluster members in the monitored field are variables, illustrating the value of photometric monitoring for identifying PMS cluster members. Among this brighter sample, 14 of the 16 known K or M-type weak-line T Tauri stars (WTTS) were found to be periodic variables, while all five of the known classical T Tauri stars (CTTS) were found to be irregular variables. In the full sample, which includes 150 stars with I as faint as 18, we find that 40% of the 63 WTTS are detected as variables, nearly all of them periodic, while 55% of the 20 CTTS are also detected as variable, with none of them periodic.
- ID:
- ivo://CDS.VizieR/J/MNRAS/376/580
- Title:
- Cousins RI photometry of NGC 2169
- Short Name:
- J/MNRAS/376/580
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used Cousins RI CCD photometry from the Isaac Newton telescope and intermediate-resolution spectroscopy from the Gemini North telescope to identify and characterize low-mass (0.15<M/M_{sun}_<1.3) pre-main-sequence stars in the young open cluster NGC 2169. Isochrone fitting to the high- and low-mass populations yields an intrinsic distance modulus of 10.13^+0.06^_-0.09_mag and a model-dependent age of 9+/-2Myr. Compared to the nearby, kinematically defined groups of a similar age, NGC 2169 has a large low-mass population which potentially offers a more precise statistical investigation of several aspects of star formation and early stellar evolution. By modelling the distribution of low-mass stars in the IC versus RC IC diagram, we find that any age spread among cluster members has a Gaussian full width at half-maximum (FWHM) 2.5Myr. A young age and a small age spread (<10Myr) are supported by the lack of significant lithium depletion in the vast majority of cluster members. There is no clear evidence for accretion or warm circumstellar dust in the low-mass members of NGC 2169, bolstering the idea that strong accretion has ceased and inner discs have dispersed in almost all low-mass stars by ages of 10Myr.
- 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.
- 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/A+A/636/A65
- Title:
- DG Tau B ALMA observations
- Short Name:
- J/A+A/636/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical composition of planets is determined by the distribution of the various molecular species in the protoplanetary disk at the time of their formation. To date, only a handful of disks have been imaged in multiple spectral lines with high spatial resolution. As part of a small campaign devoted to the chemical characterization of disk-outflow sources in Taurus, we report on new ALMA Band 6 (1.3mm) observations with 0.15" (20au) resolution toward the embedded young star DG Tau B. Images of the continuum emission reveals a dust disk with rings and, putatively, a leading spiral arm. The disk, as well as the prominent outflow cavities, are detected in CO, H_2_CO, CS, and CN; instead, they remain undetected in SO_2_, HDO, and CH_3_OH. From the absorption of the back-side outflow, we inferred that the disk emission is optically thick in the inner 50au. This morphology explains why no line emission is detected from this inner region and poses some limitations toward the calculation of the dust mass and the characterization of the inner gaseous disk. The H_2_CO and CS emission from the inner 200au is mostly from the disk, and their morphology is very similar. The CN emission significantly differs from the other two molecules as it is observed only beyond 150au. This ring-like morphology is consistent with previous observations and the predictions of thermochemical disk models. Finally, we constrained the disk-integrated column density of all molecules. In particular, we found that the CH_3_OH/H_2_CO ratio must be smaller than ~2, making the methanol non-detection still consistent with the only such ratio available from the literature (1.27 in TW Hya).
- ID:
- ivo://CDS.VizieR/J/A+A/642/A56
- Title:
- Diagnostic for accretion/outflow in NGC 2264
- Short Name:
- J/A+A/642/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 2264 is a young cluster whose accretion properties can be investigated in detail by taking advantage of the FLAMES data in the context of the Gaia-ESO Survey. In fact, the analysis of the H{alpha} emission line profile can provide us with information about the accretion and ejection activity of young stars. However, a strong nebular emission that contributes to the H{alpha} emission can alter the profiles, with consequences for their physical interpretation. Our study is aimed at investigating the accretion and ejection properties of NGC 2264 by applying a proper treatment of the sky contribution to the H{alpha} and forbidden emission lines (FELs; [SII] and [NII] doublets). We developed a tool, the OH{alpha}NA-method, to handle the strong nebular contribution and spectra with spurious profiles of the H{alpha} and FELs, namely altered H{alpha} profiles or absorption features artificially created where emission lines (FELs) are expected. We derived the quantitative measurements of relevant parameters to describe the accretion and ejection processes in young members of NGC 2264, focusing on reliable quantities derived from the width of the lines, which is relatively unaffected by the nebular emission, unlike the intensity peak, which can be altered significantly. We derive the quantitative measurements related to the H{alpha} emission line and discuss the comparison between the original and sky-subtracted spectra. We thus reveal possible profile alterations with consequences for their physical interpretation. Furthermore, we show the analysis of the variability for multi-epoch observations, also deriving the velocity of the infalling and outflowing plasma from the wings of the broad H{alpha} emission line (in accreting stars). We also explore the mass accretion rate versus full width at zero intensity of the H{alpha} line, namely dM/dt versus FWZI(H{alpha}), a correlation based on the width of the emission line, which is expected to be more robust with respect to any measurement derived from the peak (e.g., H{alpha}_10%_) and possibly altered by the nebular contribution. We are able to ascertain that more than 20% of the confirmed accretors, which have already been identified in NGC 2264, are affected by the alteration of their line profiles due to the contribution of the nebular emission. Therefore, this is an important issue to consider when investigating accretion and ejection processes in young stellar clusters. While a small fraction of spectra can be unequivocally classified as either unaffected by nebular emission or dominated by nebular emission, the majority (>90%) represent intermediate cases whose spectral features have to be investigated in detail to derive reliable measurements of the relevant parameters and their physical implications.
