- ID:
- ivo://CDS.VizieR/J/ApJ/850/34
- Title:
- 3000-25000{AA} spectroscopy of nearby M dwarfs
- Short Name:
- J/ApJ/850/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent studies of the stellar population in the solar neighborhood (<20pc) suggest that there are undetected white dwarfs (WDs) in multiple systems with main-sequence companions. Detecting these hidden stars and obtaining a more complete census of nearby WDs is important for our understanding of stellar and galactic evolution, as well as the study of explosive phenomena. In an attempt to uncover these hidden WDs, we present intermediate resolution spectroscopy over the wavelength range of 3000-25000{AA} of 101 nearby M dwarfs (dMs), observed with the Very Large Telescope X-Shooter spectrograph. For each star we search for a hot component superimposed on the dM spectrum. X-Shooter has excellent blue sensitivity and thus can reveal a faint hot WD despite the brightness of its red companion. Visual examination shows no clear evidence of a WD in any of the spectra. We place upper limits on the effective temperatures of WDs that may still be hiding by fitting dM templates to the spectra and modeling the WD spectra. On average our survey is sensitive to WDs hotter than about 5300K. This suggests that the frequency of WD companions of Teff>~5300K with separation of the order of <~50 au among the local dM population is <3% at the 95% confidence level.
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- ID:
- ivo://CDS.VizieR/J/ApJS/192/2
- Title:
- A Bayesian search for binaries in Hipparcos
- Short Name:
- J/ApJS/192/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop Bayesian statistical methods for discovering and assigning probabilities to non-random (e.g., physical) stellar companions. These companions are either presently bound or were previously bound. The probabilities depend on similarities in corrected proper motion parallel and perpendicular to the brighter component's motion, parallax, and the local phase-space density of field stars. Control experiments are conducted to understand the behavior of false positives. The technique is applied to the Hipparcos Catalogue (Cat. I/239) within 100pc. This is the first all-sky survey to locate escaped companions still drifting along with each other. In the <100pc distance range, ~220 high probability companions with separations between 0.01 and 1pc are found. The first evidence for a population (~300) of companions separated by 1-8pc is found.
- ID:
- ivo://CDS.VizieR/J/AJ/138/1622
- Title:
- Absolute properties of LV Her
- Short Name:
- J/AJ/138/1622
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report extensive spectroscopic and differential V-band photometric observations of the 18.4 day detached double-lined eclipsing binary LV Her (F9V), which has the highest eccentricity (e~0.613) among the systems with well-measured properties. We determine the absolute masses and radii of the components to be M1=1.193+/-0.010M_{sun}_, M2=1.1698+/-0.0081M_{sun}_, R1=1.358+/-0.012R_{sun}_, and R2=1.313+/-0.011R_{sun}_, with fractional errors of 0.9% or better. The effective temperatures are 6060+/-150K and 6030+/-150K, respectively, and the overall metallicity is estimated to be [m/H]=+0.08+/-0.21. A comparison with current stellar evolution models for this composition indicates an excellent fit for an age between 3.8 and 4.2Gyr, with both stars being near the middle of their main-sequence lifetimes. Full integration of the equations for tidal evolution is consistent with the high eccentricity, and suggests that the stars' spin axes are aligned with the orbital axis, and that their rotations should be pseudo-synchronized. The latter prediction is not quite in agreement with the measured projected rotational velocities.
- ID:
- ivo://CDS.VizieR/J/AJ/161/285
- Title:
- Absorption & emission lines and RVel for vA 351
- Short Name:
- J/AJ/161/285
- Date:
- 08 Mar 2022
- Publisher:
- CDS
- Description:
- We extend results first announced by Franz et al., that identified vA351=H346 in the Hyades as a multiple star system containing a white dwarf. With Hubble Space Telescope Fine Guidance Sensor fringe tracking and scanning, and more recent speckle observations, all spanning 20.7years, we establish a parallax, relative orbit, and mass fraction for two components, with a period, P=2.70yr and total mass 2.1M{sun}. With ground-based radial velocities from the McDonald Observatory Otto Struve 2.1m Telescope Sandiford Spectrograph, and Center for Astrophysics Digital Speedometers, spanning 37 years, we find that component B consists of BC, two M-dwarf stars orbiting with a very short period (P_BC_=0.749days), having a mass ratio M_C_/M_B_=0.95. We confirm that the total mass of the system can only be reconciled with the distance and component photometry by including a fainter, higher-mass component. The quadruple system consists of three M dwarfs (A, B, C) and one white dwarf (D). We determine individual M-dwarf masses M_A_=0.53{+/-}0.10M{sun}, M_B_=0.43{+/-}0.04M{sun}, and M_C_=0.41{+/-}0.04M{sun}. The white dwarf mass, 0.54{+/-}0.04M{sun}, comes from cooling models, an assumed Hyades age of 670Myr, and consistency with all previous and derived astrometric, photometric, and radial velocity results. Velocities from H{alpha} and HeI emission lines confirm the BC period derived from absorption lines, with similar (HeI) and higher (H{alpha}) velocity amplitudes. We ascribe the larger H{alpha} amplitude to emission from a region each component shadows from the other, depending on the line of sight.
- ID:
- ivo://CDS.VizieR/J/ApJS/245/34
- Title:
- Abundances for 6 million stars from LAMOST DR5
- Short Name:
- J/ApJS/245/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the determination of stellar parameters and individual elemental abundances for 6 million stars from ~8 million low-resolution (R~1800) spectra from LAMOST DR5. This is based on a modeling approach that we dub the data-driven Payne (DD-Payne), which inherits essential ingredients from both the Payne and the Cannon. It is a data-driven model that incorporates constraints from theoretical spectral models to ensure the derived abundance estimates are physically sensible. Stars in LAMOST DR5 that are in common with either GALAH DR2 or APOGEE DR14 are used to train a model that delivers stellar parameters (Teff, log g, Vmic) and abundances for 16 elements (C, N, O, Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, and Ba) over a metallicity range of -4dex<[Fe/H]<0.6dex when applied to the LAMOST spectra. Cross-validation and repeat observations suggest that, for S/N_pixel_>=50, the typical internal abundance precision is 0.03-0.1dex for the majority of these elements, with 0.2-0.3dex for Cu and Ba, and the internal precision of Teff and logg is better than 30K and 0.07dex, respectively. Abundance systematics at the ~0.1dex level are present in these estimates but are inherited from the high-resolution surveys' training labels. For some elements, GALAH provides more robust training labels, for others, APOGEE. We provide flags to guide the quality of the label determination and identify binary/multiple stars in LAMOST DR5.
- ID:
- ivo://CDS.VizieR/J/ApJ/736/87
- Title:
- Abundances in G-type stars with exoplanets
- Short Name:
- J/ApJ/736/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We confirm the difference in chemical abundance between stars with and without exoplanets and present the relation between chemical abundances and physical properties of exoplanets, such as planetary mass and the semimajor axis of planetary orbit. We obtained the spectra of 52 G-type stars from the Bohyunsan Optical Astronomy Observatory (BOAO) Echelle Spectrograph and carried out abundance analyses for 12 elements: Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni. We first found that the [Mn/Fe] ratios of planet-host stars are higher than those of comparison stars over the entire metallicity range, and we then found that in metal-poor stars of [Fe/H]<-0.4 the abundance difference was larger than in metal-rich samples, especially for the elements of Mg, Al, Sc, Ti, V, and Co. After examining the relation between planet properties and metallicities of planet-host stars, we observed that planet-host stars with low metallicities tend to have several low-mass planets (<M_J_) instead of a massive gas-giant planet.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/L12
- Title:
- Abundances in host stars XO-2S and XO-2N
- Short Name:
- J/ApJ/768/L12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the aim of connecting the compositions of stars and planets, we present the abundances of carbon and oxygen, as well as iron and nickel, for the transiting exoplanet host star XO-2N and its wide-separation binary companion XO-2S. Stellar parameters are derived from high-resolution, high signal-to-noise spectra, and the two stars are found to be similar in their T_eff_, log g, iron ([Fe/H]), and nickel ([Ni/H]) abundances. Their carbon ([C/H]) and oxygen ([O/H]) abundances also overlap within errors, although XO-2N may be slightly more C-rich and O-rich than XO-2S. The C/O ratios of both stars (~0.60+/-0.20) may also be somewhat larger than solar (C/O~0.50). The XO-2 system has a transiting hot Jupiter orbiting one binary component but not the other, allowing us to probe the potential effects planet formation might have on the host star composition. Additionally, with multiple observations of its atmosphere the transiting exoplanet XO-2b lends itself to compositional analysis, which can be compared to the natal chemical environment established by our binary star elemental abundances. This work sets the stage for determining how similar or different exoplanet and host star compositions are, and the implications for planet formation, by discussing the C/O ratio measurements in the unique environment of a visual binary system with one star hosting a transiting hot Jupiter.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/L32
- Title:
- Abundances of 16 Cyg A and B
- Short Name:
- J/ApJ/737/L32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of a detailed abundance analysis of the solar twins 16 Cyg A and 16 Cyg B based on high-resolution, high signal-to-noise ratio echelle spectroscopy are presented. 16 Cyg B is known to host a giant planet while no planets have yet been detected around 16 Cyg A. Stellar parameters are derived directly from our high-quality spectra, and the stars are found to be physically similar, with {Delta}T_eff_=+43K, {Delta}logg=-0.02dex, and {Delta}{xi}=+0.10km/s (in the sense of A-B), consistent with previous findings. Abundances of 15 elements are derived and are found to be indistinguishable between the two stars. The abundances of each element differ by <=0.026dex, and the mean difference is +0.003+/-0.015({sigma}) dex. Aside from Li, which has been previously shown to be depleted by a factor of at least 4.5 in 16 Cyg B relative to 16 Cyg A, the two stars appear to be chemically identical. The abundances of each star demonstrate a positive correlation with the condensation temperature of the elements (T_c_); the slopes of the trends are also indistinguishable. In accordance with recent suggestions, the positive slopes of the [m/H]-T_c_ relations may imply that terrestrial planets have not formed around either 16 Cyg A or 16 Cyg B.
- ID:
- ivo://CDS.VizieR/J/MNRAS/492/1164
- Title:
- Abundances of Gaia DR2 wide binaries
- Short Name:
- J/MNRAS/492/1164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the high-level goals of Galactic archaeology is chemical tagging of stars across the Milky Way to piece together its assembly history. For this to work, stars born together must be uniquely chemically homogeneous. Wide binary systems are an important laboratory to test this underlying assumption. Here we present the detailed chemical abundance patterns of 50 stars across 25 wide binary systems comprised of main-sequence stars of similar spectral type identified in Gaia DR2 with the aim of quantifying their level of chemical homogeneity. Using high-resolution spectra obtained with McDonald Observatory, we derive stellar atmospheric parameters and precise detailed chemical abundances for light/odd-Z (Li, C, Na, Al, Sc, V, Cu), alpha (Mg, Si, Ca), Fe-peak (Ti, Cr, Mn, Fe, Co, Ni, Zn), and neutron capture (Sr, Y, Zr, Ba, La, Nd, Eu) elements. Results indicate that 80% (20 pairs) of the systems are homogeneous in [Fe/H] at levels below 0.02dex. These systems are also chemically homogeneous in all elemental abundances studied, with offsets and dispersions consistent with measurement uncertainties. We also find that wide binary systems are far more chemically homogeneous than random pairings of field stars of similar spectral type. These results indicate that wide binary systems tend to be chemically homogeneous but in some cases they can differ in their detailed elemental abundances at a level of [X/H]~0.10dex, overall implying chemical tagging in broad strokes can work.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/1592
- Title:
- Abundances of solar analogs with planets
- Short Name:
- J/ApJ/720/1592
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a fully differential chemical abundance analysis using very high resolution ({lambda}/{delta}{lambda}>~85000) and very high signal-to-noise (S/N~800 on average) HARPS and UVES spectra of 7 solar twins and 95 solar analogs, of which 24 are planet hosts and 71 are stars without detected planets. The whole sample of solar analogs provides very accurate Galactic chemical evolution trends in the metallicity range -0.3<[Fe/H]<0.5. Solar twins with and without planets show similar mean abundance ratios. We have also analyzed a sub-sample of 28 solar analogs, 14 planet hosts, and 14 stars without known planets, with spectra at S/N~850 on average, in the metallicity range 0.14<[Fe/H]<0.36, and find the same abundance pattern for both samples of stars with and without planets. This result does not depend on either the planet mass, from 7 Earth masses to 17.4 Jupiter masses, or the orbital period of the planets, from 3 to 4300 days. In addition, we have derived the slope of the abundance ratios as a function of the condensation temperature for each star and again find similar distributions of the slopes for both stars with and without planets. In particular, the peaks of these two distributions are placed at a similar value but with the opposite sign to that expected from a possible signature of terrestrial planets. In particular, two of the planetary systems in this sample, each of them containing a super-Earth-like planet, show slope values very close to these peaks, which may suggest that these abundance patterns are not related to the presence of terrestrial planets.
