- ID:
- ivo://CDS.VizieR/J/A+A/352/228
- Title:
- Transitional YSOs candidates
- Short Name:
- J/A+A/352/228
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We are searching for Young Stellar Objects (YSOs) near the boundary between protostars and pre-main-sequence objects, what we term Transitional YSOs. We have identified a sample of 125 objects as candidate transitional YSOs on the basis of IRAS colors and the optical appearance on POSS plates. We have obtained optical and near-IR imaging of 82 objects accessible from the Northern Hemisphere and optical images of 62 sources accessible from the South. We also created deconvolved 60{mu}m IRAS images of all sources. We have classified the objects on the basis of their morphology in the optical and near-IR images. We find that the majority of our objects are associated with star-forming regions, confirming our expectation that the bulk of these objects are YSOs. Of the 125 objects, 28 have a variety of characteristics very similar to other transitional YSOs, while another 22 show some of these characteristics. Furthermore we have found seven objects to be good candidates for members of the Herbig Ae/Be stellar group, of which three are newly identified as such.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/658/A36
- Title:
- Transition disks around evolved stars
- Short Name:
- J/A+A/658/A36
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Post-AGB binaries are surrounded by massive disks of gas and dust that are similar to protoplanetary disks surrounding young stars. We assembled a catalog of all known Galactic post-AGB binaries with disks. We explore correlations between the different observables with the aim to learn more about potential disk-binary interactions. We compiled spectral energy distributions of 85 Galactic post-AGB binary systems. We built-up a color-color diagram to differentiate between the different disk morphologies traced by the characteristics of the infrared excess. We categorised different disk types and looked for correlations with other observational characteristics of these systems. 8 to 12% of our targets are surrounded by transition disks, i.e. disks having no or low near-infrared excesses. We find a strong link between these transition disks and the depletion of refractory elements seen on the surface of the post-AGB star. We interpret this correlation as evidence for the presence of a mechanism that stimulates the dust and gas separation within the disk and which also produces the transition disk structure. We propose that such a mechanism can be a giant planet carving a hole in the disk which traps the dust in the outer disk parts. We propose two disk evolutionary scenarios, depending on the presence of such a giant planet in the disk. We advocate that giant planets can successfully explain the correlation between the transition disks and the depletion of refractory materials observed in post-AGB binaries. If the planetary scenario is confirmed, disks around post-AGB binaries could be a unique laboratory to test planet-disk interactions and their influence on the late evolution of binary stars. Whether the planets are first or second generation also remains to be studied. We argue that these disks are the perfect place to study planet formation scenarios in an unprecedented parameter space.
1103. Transition disk survey
- ID:
- ivo://CDS.VizieR/J/A+A/592/A126
- Title:
- Transition disk survey
- Short Name:
- J/A+A/592/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Understanding disk evolution and dissipation is essential for studies of planet formation. Transition disks, i.e., disks with large dust cavities and gaps, are promising candidates of active evolution. About two dozen candidates, selected by their Spectral Energy Distribution (SED), have been confirmed to have dust cavities through millimeter interferometric imaging, but this sample is biased toward the brightest disks. The Spitzer surveys of nearby low-mass star-forming regions have resulted in more than 4000 young stellar objects (YSOs). Using color criteria, we selected a sample of ~150 candidates and an additional 40 candidates and known transition disks from the literature. The Spitzer data were complemented by new observations at longer wavelengths, including new JCMT and APEX submillimeter photometry, and WISE and Herschel-PACS mid- and far-infrared photometry. Furthermore, optical spectroscopy was obtained and stellar types were derived for 85% of the sample, including information from the literature. The SEDs were fit to a grid of RADMC-3D disk models with a limited number of parameters: disk mass, inner disk mass, scale height and flaring, and disk cavity radius, where the latter is the main parameter of interest. About 72% of our targets possibly have dust cavities based on the SED. The derived cavity sizes are consistent with imaging/modeling results in the literature, where available. Trends are found with the L_disk_ over L_*_ ratio and stellar mass and a possible connection with exoplanet orbital radii. A comparison with a previous study where color observables are used (Cieza et al., 2010, Cat. J/ApJ/712/925) reveals large overlap between their category of planet-forming disks and our transition disks with cavities. A large number of the new transition disk candidates are suitable for follow-up observations with ALMA.
- ID:
- ivo://CDS.VizieR/J/ApJ/893/27
- Title:
- TRENDS high-contrast imaging survey. VIII.
- Short Name:
- J/ApJ/893/27
- Date:
- 19 Jan 2022 00:39:50
- Publisher:
- CDS
- Description:
- The physical properties of faint stellar and substellar objects often rely on indirect, model-dependent estimates. For example, the masses of brown dwarfs are usually inferred using evolutionary models, which are age dependent and have yet to be properly calibrated. With the goal of identifying new benchmark objects to test low-mass stellar and substellar models, we have carried out a comprehensive adaptive optics survey as part of the TaRgetting bENchmark-objects with the Doppler Spectroscopy (TRENDS) high-contrast imaging program. Using legacy radial velocity measurements from the High Resolution Echelle Spectrometer at Keck, we have identified several dozen stars that show long-term Doppler accelerations. We present follow-up high-contrast observations from the campaign and report the discovery of 31 comoving companions, as well as 11 strong candidate companions, to solar-type stars with well-determined parallax and metallicity values. Benchmark objects of this nature lend themselves to orbit determinations, dynamical mass estimates, and independent compositional assessment. This compendium of benchmark objects will serve as a convenient test group to substantiate theoretical evolutionary and atmospheric models near the hydrogen fusing limit.
- ID:
- ivo://CDS.VizieR/J/ApJ/893/56
- Title:
- T Tauri star IR excesses & Ha eq. widths
- Short Name:
- J/ApJ/893/56
- Date:
- 19 Jan 2022 11:42:19
- Publisher:
- CDS
- Description:
- We present a study of the evolution of the inner few astronomical units of protoplanetary disks around low-mass stars. We consider nearby stellar groups with ages spanning from 1 to 11Myr, distributed into four age bins. Combining PANSTARSS photometry with spectral types, we derive the reddening consistently for each star, which we use (1) to measure the excess emission above the photosphere with a new indicator of IR excess and (2) to estimate the mass accretion rate (dM/dt) from the equivalent width of the H{alpha} line. Using the observed decay of dM/dt as a constraint to fix the initial conditions and the viscosity parameter of viscous evolutionary models, we use approximate Bayesian modeling to infer the dust properties that produce the observed decrease of the IR excess with age, in the range between 4.5 and 24{mu}m. We calculate an extensive grid of irradiated disk models with a two-layered wall to emulate a curved dust inner edge and obtain the vertical structure consistent with the surface density predicted by viscous evolution. We find that the median dust depletion in the disk upper layers is {epsilon}~3x10^-3^ at 1.5Myr, consistent with previous studies, and it decreases to {epsilon}~3x10^-4^ by 7.5Myr. We include photoevaporation in a simple model of the disk evolution and find that a photoevaporative wind mass-loss rate of ~1-3x10^-9^M_{sun}_/yr agrees with the decrease of the disk fraction with age reasonably well. The models show the inward evolution of the H_2_O and CO snowlines.
- ID:
- ivo://CDS.VizieR/J/A+A/519/A83
- Title:
- T Tau stars toward the Taurus-Auriga region
- Short Name:
- J/A+A/519/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for new T Tauri star (TTS) candidates with the mid-infrared (MIR) part of the AKARI All-Sky Survey at 9 and 18{mu}m wavelengths. We used the point source catalogue (PSC) obtained by the Infrared Camera (IRC) on board AKARI. We combined the 2MASS PSC and the 3rd version of the USNO CCD Astrograph Catalogue (UCAC) with the AKARI IRC-PSC, and surveyed 517 known TTSs over a 1800-square-degree part of the Taurus-Auriga region to develop criteria to extract TTSs. We considered asymptotic giant branch (AGB) stars, post-AGB stars, planetary nebulae (PNe), and galaxies, which have similar MIR colours, to separate TTSs from these sources. We finally searched for new TTS candidates from AKARI IRC-PSC in the same Taurus-Auriga region. Of the 517 known TTSs, we detected 133 sources with AKARI: 46 sources were not detected by IRAS. Based on the colour-colour and colour-magnitude diagrams made from the AKARI, 2MASS, and UCAC surveys, we propose the criteria to extract TTS candidates from the AKARI All-Sky data, and 68/133 AKARI detected TTSs have passed these criteria. On the basis of our criteria, we selected 176/14725 AKARI sources as TTS candidates that are located around the Taurus-Auriga region. Comparing these sources with SIMBAD, we found that 148 are previously identified sources including 115 young stellar objects (YSOs), and 28 unidentified sources. Based on SIMBAD identifications, we infer the TTS-identification probability using our criteria to be ~75%. We find 28 TTS candidates, of which we expect ~21 to be confirmed once follow-up observations can be obtained. Although the probability of ~75% is not so high, it is affected by the completeness of the SIMBAD database, and we can search for TTSs over the whole sky, and all star-forming regions.
- ID:
- ivo://CDS.VizieR/II/108
- Title:
- Two-Micron Sky Survey, Nearest SAO Stars on POSS
- Short Name:
- II/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog is a list of potential guide stars developed for a program to obtain more precise positions of objects in the IRC Two-Micron Sky Survey of Neguebauer and Leighton (1969). For each IRC source (col. 1), it gives: (col. 2) the identification of the star in the SAO catalog which is nearest, (col. 3) the great circle arc distance (in seconds) between the SAO star and the IRC source, (col. 4) the position angle (in degrees) of the IRC source relative to the SAO star, (col. 5) the plate number(s) of the POSS on which the IRC source appears, (col. 6,7) the approximate rectangular coordinates (in mm) of the IRC source on the POSS print area with respect to the Southwest corner, and (col. 8) the modified Luyten Palomar number. The POSS plate numbers given are for the red plates.
- ID:
- ivo://CDS.VizieR/J/MNRAS/363/1111
- Title:
- Tycho-2 stars with IR excess
- Short Name:
- J/MNRAS/363/1111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stars of all evolutionary phases have been found to have excess infrared emission due to the presence of circumstellar material. To identify such stars, we have positionally correlated the infrared Mid-Course Space Experiment (MSX) Point Source Catalogue (<V/114>) and the Tycho-2 optical catalogue (<I/259>). Near-mid-infrared colour criteria have been developed to select infrared excess stars. The search yielded 1938 excess stars; over half (979) have never previously been detected by IRAS. The excess stars were found to be young objects such as Herbig Ae/Be and Be stars, and evolved objects such as OH/IR (infrared) and carbon stars. A number of B-type excess stars were also discovered whose infrared colours could not be readily explained by known catalogued objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/11
- Title:
- Type 1 vs 2 X-ray-selected COSMOS AGNs & environment
- Short Name:
- J/ApJ/878/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The unified model of active galactic nuclei (AGNs) proposes that different AGN optical spectral types are caused by different viewing angles with respect to an obscuring "torus". Therefore, this model predicts that type 1 and type 2 AGNs should have similar host-galaxy properties. We investigate this prediction with 2463 X-ray-selected AGNs in the COSMOS field. We divide our sample into type 1 and type 2 AGNs based on their spectra, morphologies, and variability. We derive their host-galaxy stellar masses (M_*_) through spectral energy distribution (SED) fitting, and we find that the hosts M_*_ of type 1 AGNs tend to be slightly smaller than those of type 2 AGNs by {Delta}logM_*_~0.2dex (~4{sigma} significance). Besides deriving star formation rates (SFRs) from SED fitting, we also utilize far-infrared (FIR) photometry and a stacking method to obtain FIR-based SFRs. We find that the SFRs of type 1 and type 2 sources are similar once their redshifts and X-ray luminosities are controlled. We also investigate the cosmic environment, and we find that the surface number densities (sub-Mpc) and cosmic-web environments (~1-10Mpc) are similar for both populations. In summary, our analyses show that the host galaxies of type 1 and type 2 AGNs have similar SFRs and cosmic environments in general, but the former tend to have a lower M_*_ than the latter. The difference in M_*_ indicates that the AGN unification model is not strictly correct, and both host galaxy and torus may contribute to the optical obscuration of AGNs.
- ID:
- ivo://CDS.VizieR/J/other/PZ/29.1
- Title:
- UBV light curves of V354 Lac
- Short Name:
- J/other/PZ/29.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New photometry obtained in 2000-2008 is presented for the post-AGB star IRAS 22272+5435 = V354 Lac. The star showed semi-regular light variations with varying amplitudes.
