- ID:
- ivo://CDS.VizieR/J/A+A/427/933
- Title:
- Precise temperature of F-K field dwarfs
- Short Name:
- J/A+A/427/933
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Highly precise temperatures (sigma=10-15K) have been determined from line depth ratios for a set of 248 F-K field dwarfs of about solar metallicity (-0.5<[Fe/H]<+0.4), based on high resolution (R=42000), high S/N echelle spectra. A new gap has been discovered in the distribution of stars on the Main Sequence in the temperature range 5560 to 5610K. This gap coincides with a jump in the microturbulent velocity Vt and the well-known Li depression near 5600K in field dwarfs and open clusters. As the principal cause of the observed discontinuities in stellar properties we propose the penetration of the convective zone into the inner layers of stars slightly less massive than the Sun and related to it, a change in the temperature gradient.
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- ID:
- ivo://CDS.VizieR/J/AJ/137/1
- Title:
- Proper motions and astrometry of late-type dwarfs
- Short Name:
- J/AJ/137/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report proper-motion measurements for 427 late-type M, L, and T dwarfs, 332 of which have been measured for the first time. Combining these new proper motions with previously published measurements yields a sample of 841 M7-T8 dwarfs. We combined parallax measurements or calculated spectrophotometric distances, and computed tangential velocities for the entire sample.
- ID:
- ivo://CDS.VizieR/J/AJ/154/46
- Title:
- Proper motions and photometry for members of Cha I
- Short Name:
- J/AJ/154/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a search for planetary-mass brown dwarfs in the Chamaeleon I star-forming region using proper motions and photometry measured from optical and infrared images from the Spitzer Space Telescope, the Hubble Space Telescope, and ground-based facilities. Through near-IR spectroscopy at Gemini Observatory, we have confirmed six of the candidates as new late-type members of Chamaeleon I ({>=}M8). One of these objects, ChaJ11110675-7636030, has the faintest extinction-corrected M_K_ among known members, which corresponds to a mass of 3-6M_Jup_ according to evolutionary models. That object and two other new members have redder mid-IR colors than young photospheres at {<=}M9.5, which may indicate the presence of disks. However, since those objects may be later than M9.5 and the mid-IR colors of young photospheres are ill-defined at those types, we cannot determine conclusively whether color excesses from disks are present. If ChaJ11110675-7636030 does have a disk, it would be a contender for the least-massive known brown dwarf with a disk. Since the new brown dwarfs that we have found extend below our completeness limit of 6-10M_Jup_, deeper observations are needed to measure the minimum mass of the initial mass function in Chamaeleon I.
- ID:
- ivo://CDS.VizieR/J/MNRAS/384/1399
- Title:
- Proper motions of field L and T dwarfs
- Short Name:
- J/MNRAS/384/1399
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The proper motion measurements for 142 previously known L and T dwarfs are presented. From this sample we identify and discuss eight high-velocity L dwarfs. We also find four new wide common proper motion binaries/multiple systems. Using the moving cluster methods we have also identified a number of L dwarfs that may be members of the Ursa Major (age~400Myr), the Hyades (age~625Myr) and the Pleiades (age~125Myr) moving groups.
- ID:
- ivo://CDS.VizieR/J/MNRAS/390/1517
- Title:
- Proper motions of field L and T dwarfs
- Short Name:
- J/MNRAS/390/1517
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By using images taken with Wide Field Camera (WFCAM) on United Kingdom Infrared Telescope (UKIRT) and Son of ISAAC (SofI) on the New Technology Telescope (NTT) and combining them with Two Micron All Sky Survey (2MASS) we have measured proper motions for 125 L and T dwarfs in the dwarf archive. Two of these L dwarfs appear to have M dwarf common proper motion companions, and two also appear to be high-velocity dwarfs, indicating possible membership of the thick disc. We have also compared the motion of these 125 objects to that of numerous moving groups, and have identified new members of the Hyades, Ursa Major and Pleiades moving groups. These new objects, as well as those identified in Jameson et al. have allowed us to refine the L dwarf sequence for Ursa Major that was defined by Jameson et al, 2008 (Cat. J/MNRAS/384/1399).
- ID:
- ivo://CDS.VizieR/J/PASJ/59/335
- Title:
- Properties of 160 F-K disk dwarfs/subgiants
- Short Name:
- J/PASJ/59/335
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The properties of 160 F, G, and K disk dwarfs/subgiants (including 27 planet-host stars) mostly within -0.6<~[Fe/H]<~+0.4, the Okayama Astrophysical Observatory spectrum collection of which had been made open to the public recently, were extensively investigated with particular attention to determining (1) the mass and the age with the help of theoretical stellar evolution calculations, (2) the kinematic parameters of orbital motions in the Galaxy, and (3) the abundances of 15 elements (Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, and Zn) by analyzing the spectra in this database. The resulting characteristics are discussed in terms of several relevant topics of interest, such as a validity check for assuming LTE, the [X/Fe] vs. [Fe/H] diagram containing information on the chemical evolution of the Galactic disk, the age-metallicity-kinematics relation, and the difference/similarity between stars with and without planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/102
- Title:
- Properties of late M-dwarfs
- Short Name:
- J/ApJ/789/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distribution of multiplicity among low-mass stars is a key issue to understanding the formation of stars and brown dwarfs, and recent surveys have yielded large enough samples of nearby low-mass stars to study this issue statistically to good accuracy. Previously, we have presented a multiplicity study of ~700 early/mid M-type stars observed with the AstraLux high-resolution Lucky Imaging cameras. Here, we extend the study of multiplicity in M-type stars through studying 286 nearby mid/late M-type stars, bridging the gap between our previous study and multiplicity studies of brown dwarfs. Most of the targets have been observed more than once, allowing us to assess common proper motion to confirm companionship. We detect 68 confirmed or probable companions in 66 systems, of which 41 were previously undiscovered. Detections are made down to the resolution limit of ~100 mas of the instrument. The raw multiplicity in the AstraLux sensitivity range is 17.9%, leading to a total multiplicity fraction of 21%-27% depending on the mass ratio distribution, which is consistent with being flat down to mass ratios of ~0.4, but cannot be stringently constrained below this value. The semi-major axis distribution is well represented by a log-normal function with {mu}_a_= 0.78 and {sigma}_a_= 0.47, which is narrower and peaked at smaller separations than for a Sun-like sample. This is consistent with a steady decrease in average semi-major axis from the highest-mass binary stars to the brown dwarf binaries.
- ID:
- ivo://CDS.VizieR/J/AJ/156/213
- Title:
- Properties of N2K stars & new gas giant companions
- Short Name:
- J/AJ/156/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The N2K planet search program was designed to exploit the planet-metallicity correlation by searching for gas giant planets orbiting metal-rich stars. Here, we present the radial velocity measurements for 378 N2K target stars that were observed with the HIRES spectrograph at Keck Observatory between 2004 and 2017. With this data set, we announce the discovery of six new gas giant exoplanets: a double-planet system orbiting HD 148164 (Msini of 1.23 and 5.16 M_JUP_) and single planet detections around HD 55696 (Msini=3.87 M_JUP_), HD 98736 (Msini=2.33 M_JUP_), HD 203473 (Msini=7.8 M_JUP_), and HD 211810 (Msini=0.67 M_JUP_). These gas giant companions have orbital semimajor axes between 1.0 and 6.2 au and eccentricities ranging from 0.13 to 0.71. We also report evidence for three gravitationally bound companions with Msini between 20 and 30 M_JUP_, placing them in the mass range of brown dwarfs, around HD 148284, HD 214823, and HD 217850, and four low-mass stellar companions orbiting HD 3404, HD 24505, HD 98630, and HD 103459. In addition, we present updated orbital parameters for 42 previously announced planets. We also report a nondetection of the putative companion HD 73256 b. Finally, we highlight the most promising candidates for direct imaging and astrometric detection, and we find that many hot Jupiters from our sample could be detectable by state-of-the-art telescopes such as Gaia.
- ID:
- ivo://CDS.VizieR/J/AJ/155/112
- Title:
- Radial velocities & light curves for HATS-43-HATS-46
- Short Name:
- J/AJ/155/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of four short-period extrasolar planets transiting moderately bright stars from photometric measurements of the HATSouth network coupled to additional spectroscopic and photometric follow-up observations. While the planet masses range from 0.26 to 0.90 M_J_, the radii are all approximately a Jupiter radii, resulting in a wide range of bulk densities. The orbital period of the planets ranges from 2.7 days to 4.7 days, with HATS-43b having an orbit that appears to be marginally non-circular (e=0.173+/-0.089). HATS-44 is notable for having a high metallicity ([Fe/H]=0.320+/-0.071). The host stars spectral types range from late F to early K, and all of them are moderately bright (13.3<V<14.4), allowing the execution of future detailed follow-up observations. HATS-43b and HATS-46b, with expected transmission signals of 2350 ppm and 1500 ppm, respectively, are particularly well suited targets for atmospheric characterization via transmission spectroscopy.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A116
- Title:
- Radial velocities of K-M dwarfs
- Short Name:
- J/A+A/596/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this paper is to present complete radial-velocity data for the spectroscopically selected McCormick (MCC) sample of nearby K-M dwarfs and, based on these data, to determine the space-velocity distributions of late-type stars in the solar neighborhood.
