- 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.
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Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/PAZh/25/30
- Title:
- UBV photometry of IRAS 18062+2410
- Short Name:
- J/PAZh/25/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The photometric and spectroscopic observations of IRAS 18062+2410 = V886 Her, a candidate for protoplanetary objects, in 1996-1997 are presented. The star exhibits rapid light variations with an amplitude up to 0.3mag in V. A high-resolution spectrum of IRAS shows absorption lines of H, HeI, OI, FeII, SiII, NaI and other species, including [OII], [NII], and [FeII] that belong to the stellar envelope.
- ID:
- ivo://CDS.VizieR/II/316
- Title:
- UKIDSS-DR6 Galactic Plane Survey
- Short Name:
- II/316
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UKIDSS Galactic Plane Survey (GPS) is one of the five near infrared Public Legacy Surveys that are being undertaken by the UKIDSS consortium, using the Wide Field Camera on the United Kingdom Infrared Telescope. It is surveying 1868 deg^2^ of the northern and equatorial Galactic plane at Galactic latitudes -5{deg}<b<5{deg} in the J, H and K filters and a ~300 deg^2^ area of the Taurus-Auriga-Perseus molecular cloud complex in these three filters and the 2.12{mu}m (1-0)S(1)H_2_ filter. It will provide data on ~ 3x10^9^ sources. The survey use the Wide Field Camera (WFCAM, see Casali et al. 2007A&A...467..777C) on the United Kingdom Infrared Telescope (UKIRT). The typical 90% completeness limits in uncrowded fields are K=18.0, H=18.75, J=19.5, with uncertainties of about 0.2mag.
- ID:
- ivo://CDS.VizieR/II/310
- Title:
- UKIDSS-DR7 Large Area Survey
- Short Name:
- II/310
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UKIRT Infrared Deep Sky Survey (UKIDSS) is a large-scale near-IR survey which aim is to cover 7500 square degrees of the Northern sky. The survey is carried out using the Wide Field Camera (WFCAM), with a field of view of 0.21 square degrees, mounted on the 3.8m United Kingdom Infra-red Telescope (UKIRT) in Hawaii. The Large Area Survey (LAS) covers an area of 4000 square degrees in high Galactic latitudes (extragalactic) in the four bands Y(1.0um) J(1.2um) H(1.6um) and K(2.2um) to a depth of K = 18.4. Details of the survey can be found in the in the paper by Lawrence et al. (2007MNRAS.379.1599L)