- ID:
- ivo://CDS.VizieR/J/AJ/155/54
- Title:
- TBOSS Survey. II. ALMA continuum observations
- Short Name:
- J/AJ/155/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 885 {mu}m ALMA continuum flux densities for 24 Taurus members spanning the stellar/substellar boundary with spectral types from M4 to M7.75. Of the 24 systems, 22 are detected at levels ranging from 1.0 to 55.7 mJy. The two nondetections are transition disks, though other transition disks in the sample are detected. Converting ALMA continuum measurements to masses using standard scaling laws and radiative transfer modeling yields dust mass estimates ranging from ~0.3 to 20 M_{Earth}_. The dust mass shows a declining trend with central object mass when combined with results from submillimeter surveys of more massive Taurus members. The substellar disks appear as part of a continuous sequence and not a distinct population. Compared to older Upper Sco members with similar masses across the substellar limit, the Taurus disks are brighter and more massive. Both Taurus and Upper Sco populations are consistent with an approximately linear relationship in M_dust_ to M_star_, although derived power-law slopes depend strongly upon choices of stellar evolutionary model and dust temperature relation. The median disk around early-M stars in Taurus contains a comparable amount of mass in small solids as the average amount of heavy elements in Kepler planetary systems on short-period orbits around M-dwarf stars, with an order of magnitude spread in disk dust mass about the median value. Assuming a gas-to-dust ratio of 100:1, only a small number of low-mass stars and brown dwarfs have a total disk mass amenable to giant planet formation, consistent with the low frequency of giant planets orbiting M dwarfs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/574/A29
- Title:
- Tc IV, Tc V and Tc VI oscillator strengths
- Short Name:
- J/A+A/574/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of technetium (Tc) in the atmospheres of red giants by Merrill (1952ApJ...116...21M) constituted convincing proof that s-process nucleosynthesis is indeed occurring in evolved stars. In principle, Tc should still be present in the atmospheres of hot post-AGB stars and (pre-) white dwarfs although, due to radioactive decay, it should be present in decreasing quantities along post-AGB evolution. The recent discovery of a large number of trans-iron group elements in hot white dwarfs with atomic numbers in the range A=30-56 (Zn to Ba) raises the prospect that Tc (A=43) may also be detected. However, this is currently not feasible because no atomic data exist for ionization stages beyond TcII. As an initial step, we calculated atomic energy levels and oscillator strengths of Tc IV-VI and used these data to compute non-local thermodynamic equilibrium (NLTE) model atmospheres to estimate at which minimum abundance level Tc could be detected. We show that Tc lines can be found in ultraviolet spectra of hot white dwarfs provided Tc is as abundant as other detected trans-Fe elements. We find that radiative levitation can keep Tc in large, easily detectable quantities in the atmosphere. A direct identification of Tc lines is still not feasible because wavelength positions cannot be computed with necessary precision. Laboratory measurements are necessary to overcome this problem. Our results suggest that such efforts are beneficial to the astrophysical community.
18573. T1C photometry of NGC7507
- ID:
- ivo://CDS.VizieR/J/A+A/555/A56
- Title:
- T1C photometry of NGC7507
- Short Name:
- J/A+A/555/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There is strong evidence that globular cluster systems (GCSs) of massive galaxies are largely assembled by infall/accretion processes. Therefore, we expect the GCSs of isolated elliptical galaxies to be poor. Although not completely isolated, NGC 7507 is a massive field elliptical galaxy with an apparently very low dark matter content. We determine the richness, the colour distribution, and the structural properties of the GCS of NGC 7507. We performed wide-field Washington photometry with data obtained with the MOSAIC II camera at the 4m-Blanco telescope (CTIO, Chile).
- ID:
- ivo://CDS.VizieR/II/270
- Title:
- TCS-CAIN: NIR Survey of the Galactic plane
- Short Name:
- II/270
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a deep multi-colour NIR survey (TCS-CAIN) that has been recently completed at the Instituto de Astrofisica de Canarias (Spain). The survey is of selected areas distributed along the Galactic plane and it goes deeper than 2MASS or DENIS. Its aim was to explore the large-scale structure of the Milky Way and the Galactic components, in particular the Galactic bar. This survey has about 10 million point-source detections in J, H, and Ks filters with a photometric accuracy of about 0.1mag in the three bands and a positional accuracy of about 0.2" (based on the 2MASS catalogue as the astrometric reference).
- ID:
- ivo://CDS.VizieR/J/ApJ/743/141
- Title:
- T dwarf companions around M, L, T dwarfs in IR
- Short Name:
- J/ApJ/743/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report observational techniques, results, and Monte Carlo population analyses from a Spitzer Infrared Array Camera imaging survey for substellar companions to 117 nearby M, L, and T dwarf systems (median distance of 10pc, mass range of 0.6 to ~0.05M_{sun}_). The two-epoch survey achieves typical detection sensitivities to substellar companions of [4.5um]<=17.2mag for angular separations between about 7" and 165". Based on common proper motion analysis, we find no evidence for new substellar companions. Using Monte Carlo orbital simulations (assuming random inclination, random eccentricity, and random longitude of pericenter), we conclude that the observational sensitivities translate to an ability to detect 600-1100K brown dwarf companions at semimajor axes >~35AU and to detect 500-600 K companions at semimajor axes >~60AU. The simulations also estimate a 600-1100K T dwarf companion fraction of <3.4% for 35-1200AU separations and <12.4% for the 500-600K companions for 60-1000AU separations.
- ID:
- ivo://CDS.VizieR/J/ApJS/205/6
- Title:
- T dwarf population revealed by WISE
- Short Name:
- J/ApJS/205/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 87 new T dwarfs uncovered with the Wide-field Infrared Survey Explorer (WISE) and 3 brown dwarfs with extremely red near-infrared colors that exhibit characteristics of both L and T dwarfs. Two of the new T dwarfs are likely binaries with L7+/-1 primaries and mid-type T secondaries. In addition, our follow-up program has confirmed 10 previously identified T dwarfs and 4 photometrically selected L and T dwarf candidates in the literature. This sample, along with the previous WISE discoveries, triples the number of known brown dwarfs with spectral types later than T5. Using the WISE All-Sky Source Catalog we present updated color-color and color-type diagrams for all the WISE-discovered T and Y dwarfs. Near-infrared spectra of the new discoveries are presented along with spectral classifications.
- ID:
- ivo://CDS.VizieR/J/MNRAS/433/457
- Title:
- 76 T dwarfs from the UKIDSS LAS
- Short Name:
- J/MNRAS/433/457
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 76 new T dwarfs from the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). Near-infrared broad- and narrow-band photometry and spectroscopy are presented for the new objects, along with Wide-field Infrared Survey Explorer (WISE) and warm-Spitzer photometry. Proper motions for 128 UKIDSS T dwarfs are presented from a new two epoch LAS proper motion catalogue. We use these motions to identify two new benchmark systems: LHS 6176AB, a T8p+M4 pair and HD 118865AB, a T5.5+F8 pair. Using age constraints from the primaries and evolutionary models to constrain the radii, we have estimated their physical properties from their bolometric luminosity. We compare the colours and properties of known benchmark T dwarfs to the latest model atmospheres and draw two principal conclusions. First, it appears that the H-[4.5] and J-W2 colours are more sensitive to metallicity than has previously been recognized, such that differences in metallicity may dominate over differences in Teff when considering relative properties of cool objects using these colours. Secondly, the previously noted apparent dominance of young objects in the late-T dwarf sample is no longer apparent when using the new model grids and the expanded sample of late-T dwarfs and benchmarks. This is supported by the apparently similar distribution of late-T dwarfs and earlier type T dwarfs on reduced proper motion diagrams that we present. Finally, we present updated space densities for the late-T dwarfs, and compare our values to simulation predictions and those from WISE.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2487
- Title:
- T dwarfs in the southern hemisphere
- Short Name:
- J/AJ/126/2487
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of three new southern hemisphere T dwarfs identified in the Two Micron All Sky Survey (Cat. <II/246>). These objects, 2MASS 0348-6022, 2MASS 0516-0445, and 2MASS 2228-4310, have classifications T7, T5.5, and T6.5, respectively. Using linear absolute magnitude/spectral type relations derived from T dwarfs with measured parallaxes, we estimate spectrophotometric distances for these discoveries; the closest, 2MASS 0348-6022, is likely within 10pc of the Sun. Proper motions and estimated tangential velocities are consistent with membership in the Galactic disk population. We also list southern hemisphere T dwarf candidates that were either not found in subsequent near-infrared imaging observations and are most likely uncataloged minor planets, or have near-infrared spectra consistent with background stars.
- ID:
- ivo://CDS.VizieR/J/AJ/150/153
- Title:
- Team Keck Redshift Survey 2 (TKRS2)
- Short Name:
- J/AJ/150/153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Team Keck Redshift Survey 2 (TKRS2), a near-infrared spectral observing program targeting selected galaxies within the CANDELS subsection of the GOODS-North Field. The TKRS2 program exploits the unique capabilities of the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE), which entered service on the Keck I telescope in 2012 and contributes substantially to the study of galaxy spectral features at redshifts inaccessible to optical spectrographs. The TKRS2 project targets 97 galaxies drawn from samples that include z~2 emission-line galaxies with features observable in the JHK bands as well as lower-redshift targets with features in the Y band. We present a detailed measurement of MOSFIRE's sensitivity as a function of wavelength, including the effects of telluric features across the YJHK filters. The largest utility of our survey is in providing rest-frame-optical emission lines for z>1 galaxies, and we demonstrate that the ratios of strong, optical emission lines of z~2 galaxies suggest the presence of either higher N/O abundances than are found in z~0 galaxies or low-metallicity gas ionized by an active galactic nucleus. We have released all TKRS2 data products into the public domain to allow researchers access to representative raw and reduced MOSFIRE spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A49
- Title:
- Teegarden's Star RV and H{alpha} curves
- Short Name:
- J/A+A/627/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Teegarden's Star is the brightest and one of the nearest ultra-cool dwarfs in the solar neighbourhood. For its late spectral type (M7.0 V), the star shows relatively little activity and is a prime target for near-infrared radial velocity surveys such as CARMENES. As part of the CARMENES search for exoplanets around M dwarfs, we obtained more than 200 radial-velocity measurements of Teegarden's Star and analysed them for planetary signals. We find periodic variability in the radial velocities of Teegarden's Star. We studied photometric measurements to rule out stellar brightness variations mimicking planetary signals. We find evidence for two planet candidates, each with 1.1M_{Earth}_ minimum mass, orbiting at periods of 4.91d and 11.4d, respectively. No evidence for planetary transits could be found in archival and follow-up photometry. Small photometric variability is suggestive of slow rotation and old age. The two planets are among the lowest-mass planets discovered so far, and they are the first Earth-mass planets around an ultra-cool dwarf for which the masses have been determined using radial velocities.