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1. 3000-25000{AA} spectroscopy of nearby M dwarfs
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.
2. A Bayesian search for binaries in Hipparcos
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.
3. Abundances for 6 million stars from LAMOST DR5
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.
4. Abundances in G-type stars with exoplanets
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.
5. Abundances in host stars XO-2S and XO-2N
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.
6. Abundances of Gaia DR2 wide binaries
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.
7. Abundances of solar analogs with planets
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.
8. Abundances of stars hosting planets
ID:
ivo://CDS.VizieR/J/ApJ/720/1290
Title:
Abundances of stars hosting planets
Short Name:
J/ApJ/720/1290
Date:
21 Oct 2021
Publisher:
CDS
Description:
The metal content of planet-hosting stars is an important ingredient that may affect the formation and evolution of planetary systems. Accurate stellar abundances require the determinations of reliable physical parameters, namely, the effective temperature, surface gravity, microturbulent velocity, and metallicity. This work presents the homogeneous derivation of such parameters for a large sample of stars hosting planets (N=117), as well as a control sample of disk stars not known to harbor giant, closely orbiting planets (N=145). Stellar parameters and iron abundances are derived from an automated analysis technique developed for this work. As previously found in the literature, the results in this study indicate that the metallicity distribution of planet-hosting stars is more metal rich by ~0.15 dex when compared to the control sample stars. A segregation of the sample according to planet mass indicates that the metallicity distribution of stars hosting only Neptunian-mass planets (with no Jovian-mass planets) tends to be more metal poor in comparison with that obtained for stars hosting a closely orbiting Jovian planet. The significance of this difference in metallicity arises from a homogeneous analysis of samples of FGK dwarfs which do not include the cooler and more problematic M dwarfs.
9. Abundances of stars with planets
ID:
ivo://CDS.VizieR/J/ApJ/732/55
Title:
Abundances of stars with planets
Short Name:
J/ApJ/732/55
Date:
21 Oct 2021
Publisher:
CDS
Description:
Precise abundances of 18 elements have been derived for 10 stars known to host giant planets from high signal-to-noise ratio, high-resolution echelle spectroscopy. Internal uncertainties in the derived abundances are typically <~0.05dex. The stars in our sample have all been previously shown to have abundances that correlate with the condensation temperature (T_c_) of the elements in the sense of increasing abundances with increasing T_c_; these trends have been interpreted as evidence that the stars may have accreted H-depleted planetary material. Our newly derived abundances also correlate positively with T_c_, although slopes of linear least-square fits to the [m/H]-T_c_ relations for all but two stars are smaller here than in previous studies. When considering the refractory elements (T_c_>900K) only, which may be more sensitive to planet formation processes, the sample can be separated into a group with positive slopes (four stars) and a group with flat or negative slopes (six stars). The four stars with positive slopes have very close-in giant planets (three at 0.05AU) and slopes that fall above the general Galactic chemical evolution trend. We suggest that these stars have accreted refractory-rich planet material but not to the extent that would increase significantly the overall stellar metallicity. The flat or negative slopes of the remaining six stars are consistent with recent suggestions of a planet formation signature, although we show that the trends may be the result of Galactic chemical evolution.
10. Accurate astrometry & RVs of 4 multiple systems
ID:
ivo://CDS.VizieR/J/ApJ/838/54
Title:
Accurate astrometry & RVs of 4 multiple systems
Short Name:
J/ApJ/838/54
Date:
21 Oct 2021
Publisher:
CDS
Description:
This work extends the still modest number of multiple stars with known relative orbit orientation. Accurate astrometry and radial velocities are used jointly to compute or update outer and inner orbits in three nearby triple systems, HIP 101955 (orbital periods 38.68 and 2.51yr), HIP 103987 (19.20 and 1.035yr), HIP 111805 (30.13 and 1.50yr), and in one quadruple system, HIP 2643 (periods 70.3, 4.85, and 0.276yr), all composed of solar-type stars. The masses are estimated from the absolute magnitudes and checked using the orbits. The ratios of outer to inner periods (from 14 to 20) and the eccentricities of the outer orbits are moderate. These systems are dynamically stable, but not very far from the stability limit. In three systems, all orbits are approximately coplanar and have small eccentricity, while in HIP101955 the inner orbit with e=0.6 is highly inclined.

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