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261. RV & light curves data for 4 G-type dwarf stars
ID:
ivo://CDS.VizieR/J/AJ/155/79
Title:
RV & light curves data for 4 G-type dwarf stars
Short Name:
J/AJ/155/79
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of four close-in transiting exoplanets (HATS-50b through HATS-53b), discovered using the HATSouth three-continent network of homogeneous and automated telescopes. These new exoplanets belong to the class of hot Jupiters and orbit G-type dwarf stars, with brightness in the range V=12.5-14.0 mag. While HATS-53 has many physical characteristics similar to the Sun, the other three stars appear to be metal-rich ([Fe/H]=0.2-0.3), larger, and more massive. Three of the new exoplanets, namely HATS-50b, HATS-51b, and HATS-53b, have low density (HATS-50b: 0.39+/-0.10 M_J_, 1.130+/-0.075 R_J_; HATS-51b: 0.768+/-0.045 M_J_, 1.41+/-0.19 R_J_; HATS-53b: 0.595+/-0.089 M_J_, 1.340+/-0.056 R_J_) and similar orbital periods (3.8297 days, 3.3489 days, 3.8538 days, respectively). Instead, HATS-52b is more dense (mass 2.24+/-0.15 M_J_ and radius 1.382+/-0.086 R_J_) and has a shorter orbital period (1.3667 days). It also receives an intensive radiation from its parent star and, consequently, presents a high equilibrium temperature (T_eq_=1834+/-73 K). HATS-50 shows a marginal additional transit feature consistent with an ultra-short-period hot super Neptune (upper mass limit 0.16 M_J_), which will be able to be confirmed with TESS photometry.
262. RV of Sigma Ori low-mass candidate members
ID:
ivo://CDS.VizieR/J/MNRAS/356/1583
Title:
RV of Sigma Ori low-mass candidate members
Short Name:
J/MNRAS/356/1583
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present radial velocities for 38 low-mass candidate members of the {sigma} Orionis young group. We have measured their radial velocities by cross-correlation of high-resolution (R>>6000) AF2/Wide Field Fibre Optical Spectrograph (WYFFOS) spectra of the gravity-sensitive NaI doublet at 8183,8195{AA}, on the nights of 2003 January 3 and 4. The total sample contained 117 objects, of which 54 have sufficient signal-to-noise ratio to detect NaI at an equivalent width of 3{AA}; however, we only detect NaI in 38 of these. This implies that very low-mass members of this young group display weaker NaI absorption than similarly aged objects in the Upper Scorpius OB association. We develop a technique to assess membership using radial velocities with a range of uncertainties that does not bias the selection when large uncertainties are present. The resulting membership probabilities are used to assess the issue of exclusion in photometric selections, and we find that very few members are likely to be excluded by such techniques. We also assess the level of contamination in the expected pre-main-sequence region of colour-magnitude space brighter than I=17. We find that contamination by non-members in the expected pre-main-sequence region of the colour-magnitude diagram is small. We conclude that although radial velocity alone is insufficient to confirm membership, high signal-to-noise ratio observations of the NaI doublet provide the opportunity to use the strength of NaI absorption in concert with radial velocities to asses membership down to the lowest masses, where lithium absorption no longer distinguishes youth.
263. RV photon limits of well-characterized F-M stars
ID:
ivo://CDS.VizieR/J/ApJS/247/11
Title:
RV photon limits of well-characterized F-M stars
Short Name:
J/ApJS/247/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
The determination of extrasolar planet masses with the radial velocity (RV) technique requires spectroscopic Doppler information from the planet's host star, which varies with stellar brightness and temperature. We analyze the Doppler information in spectra from dwarfs of spectral types F-M utilizing empirical information from HARPS and CARMENES data and model spectra. We revisit the question of whether optical or near-infrared instruments are more efficient for RV observations in low-mass stars, and we come to the conclusion that an optical setup (BVR bands) is more efficient than a near-infrared one (YJHK) in dwarf stars hotter than 3200K. We publish a catalog of 46480 well-studied F-M dwarfs in the solar neighborhood, and we compare its distribution to more than 1 million stars from Gaia DR2. For all stars, we estimate the RV photon noise achievable in typical observations under the assumption of no activity jitter and slow rotation. We find that with an ESPRESSO-like instrument at an 8m telescope, a photon noise limit of 10cm/s or lower can be reached in more than 280 stars in a 5 minute observation. At 4m telescopes, a photon noise limit of 1m/s can be reached in a 10 minute exposure in approximately 10000 predominantly Sun-like stars with a HARPS-like (optical) instrument. The same applies to ~3000 stars for a red optical setup that covers the R and I bands and ~700 stars for a near-infrared instrument. For the latter two, many of the targets are nearby M dwarfs. Finally, we identify targets in which Earth-mass planets within the liquid water habitable zone can cause RV amplitudes comparable to the RV photon noise. Assuming the same exposure times as above, we find that an ESPRESSO-like instrument can reach this limit for 1M_{Earth}_ planets in more than 1000 stars. The optical, red optical, and near-infrared configurations reach the limit for 2M_{Earth}_ planets in approximately 500, 700, and 200 stars, respectively. An online tool is provided to estimate the RV photon noise as a function of stellar temperature and brightness and wavelength coverage.
264. RVs and light curves for HATS-60-HATS-69
ID:
ivo://CDS.VizieR/J/AJ/157/55
Title:
RVs and light curves for HATS-60-HATS-69
Short Name:
J/AJ/157/55
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of 10 transiting extrasolar planets by the HATSouth survey. The planets range in mass from the super-Neptune HATS-62b, with M_p_<0.179 M_J_, to the super-Jupiter HATS-66b, with M_p_=5.33 M_J_, and in size from the Saturn HATS-69b, with R_p_=0.94 R_J_, to the inflated Jupiter HATS-67b, with R_p_=1.69 R_J_. The planets have orbital periods between 1.6092 days (HATS-67b) and 7.8180 days (HATS-61b). The hosts are dwarf stars with masses ranging from 0.89 M_{sun}_ (HATS-69) to 1.56 M_{sun}_ (HATS-64) and have apparent magnitudes between V=12.276+/-0.020 mag (HATS-68) and V=14.095+/-0.030 mag (HATS-66). The super-Neptune HATS-62b is the least massive planet discovered to date with a radius larger than Jupiter. Based largely on the Gaia DR2 distances and broadband photometry, we identify three systems (HATS-62, HATS-64, and HATS-65) as having possible unresolved binary star companions. We discuss in detail our methods for incorporating the Gaia DR2 observations into our modeling of the system parameters and into our blend analysis procedures.
265. RVs of 12 spectroscopic binaries M-dwarfs
ID:
ivo://CDS.VizieR/J/AJ/159/290
Title:
RVs of 12 spectroscopic binaries M-dwarfs
Short Name:
J/AJ/159/290
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the spectroscopic orbits of 11 nearby, mid-to-late M dwarf binary systems in a variety of configurations: 2 single-lined binaries (SB1s), 7 double-lined binaries (SB2s), 1 double-lined triple (ST2), and 1 triple-lined triple (ST3). Eight of these orbits are the first published for these systems, while five are newly identified multiples. We obtained multi-epoch, high-resolution spectra with the TRES instrument on the 1.5m Tillinghast Reflector at the Fred Lawrence Whipple Observatory located on Mt. Hopkins in AZ. Using the TiO molecular bands at 7065-7165{AA}, we calculated radial velocities for these systems, from which we derived their orbits. We find LHS 1817 to have in a 7hr period a companion that is likely a white dwarf, due to the ellipsoidal modulation we see in our MEarth-North light-curve data. We find G123-45 and LTT11586 to host companions with minimum masses of 41MJup and 44MJup with orbital periods of 35 and 15days, respectively. We find 2MA0930+0227 to have a rapidly rotating stellar companion in a 917 day orbital period. GJ268, GJ1029, LP734-34, GJ1182, G258-17, and LTT7077are SB2s with stellar companions with orbital periods of 10, 96, 34, 154, 5, and 84days; LP655-43 is an ST3 with one companion in an 18day orbital period and an outer component in a longer undetermined period. In addition, we present radial velocities for both components of L870-44AB and for the outer components of LTT11586 and LP655-43.
266. RV variability in SDSS dwarf carbon stars
ID:
ivo://CDS.VizieR/J/ApJ/877/44
Title:
RV variability in SDSS dwarf carbon stars
Short Name:
J/ApJ/877/44
Date:
21 Oct 2021
Publisher:
CDS
Description:
Dwarf carbon (dC) stars (main-sequence stars showing carbon molecular bands) were initially thought to be an oxymoron because only asymptotic giant branch (AGB) stars dredge carbon into their atmospheres. Mass transfer from a former AGB companion that has since faded to a white dwarf seems the most likely explanation. Indeed, a few types of giants known to show anomalous abundances- notably, the CH, Ba and CEMP-s stars-are known to have a high binary frequency. The dC stars may be the enhanced-abundance progenitors of most, if not all of these systems, but this requires demonstrating a high binary frequency for dCs. Here, for a sample of 240 dC stars targeted for repeat spectroscopy by the SDSS-IV's Time Domain Spectroscopic Survey, we analyze radial velocity (RV) variability to constrain the binary frequency and orbital properties. A handful of dC systems show large velocity variability (>100km/s). We compare the dCs to a control sample with a similar distribution of magnitude, color, proper motion, and parallax. Using Markov chain Monte Carlo methods, we use the measured {Delta}RV distribution to estimate the binary fraction and the separation distribution assuming both a unimodal and bimodal distribution. We find the dC stars have an enhanced binary fraction of 95%, consistent with them being products of mass transfer. These models result in mean separations of less than 1 au corresponding to periods on the order of 1 yr. Our results support the conclusion that dC stars form from close binary systems via mass transfer.
267. S abundances for 1301 stars from GES
ID:
ivo://CDS.VizieR/J/A+A/604/A128
Title:
S abundances for 1301 stars from GES
Short Name:
J/A+A/604/A128
Date:
21 Oct 2021
Publisher:
CDS
Description:
Due to their volatile nature, when sulphur and zinc are observed in external galaxies, their determined abundances represent the gas-phase abundances in the interstellar medium. This implies that they can be used as tracers of the chemical enrichment of matter in the Universe at high redshift. Comparable observations in stars are more difficult and, until recently, plagued by small number statistics. We wish to exploit the Gaia ESO Survey (GES) data to study the behaviour of sulphur and zinc abundances of a large number of Galactic stars, in a homogeneous way. By using the UVES spectra of the GES sample, we are able to assemble a sample of 1301 Galactic stars, including stars in open and globular clusters in which both sulphur and zinc were measured. We confirm the results from the literature that sulphur behaves as an alpha-element. We find a large scatter in [Zn/Fe] ratios among giant stars around solar metallicity. The lower ratios are observed in giant stars at Galactocentric distances less than 7.5kpc. No such effect is observed among dwarf stars, since they do not extend to that radius. Given the sample selection, giants and dwarfs are observed at different Galactic locations, and it is plausible, and compatible with simple calculations, that Zn-poor giants trace a younger population more polluted by SN Ia yields. It is necessary to extend observations in order to observe both giants and dwarfs at the same Galactic location. Further theoretical work on the evolution of zinc is also necessary.
268. Sample of 45 H{alpha}EW outliers
ID:
ivo://CDS.VizieR/J/AJ/161/277
Title:
Sample of 45 H{alpha}EW outliers
Short Name:
J/AJ/161/277
Date:
09 Dec 2021
Publisher:
CDS
Description:
In this work, we calibrate the relationship between H{alpha} emission and M-dwarf ages. We compile a sample of 892 M-dwarfs with H{alpha} equivalent width (H{alpha}EW) measurements from the literature that are either comoving with a white dwarf of known age (21 stars) or in a known young association (871 stars). In this sample we identify 7 M-dwarfs that are new candidate members of known associations. By dividing the stars into active and inactive categories according to their H{alpha}EW and spectral type (SpT), we find that the fraction of active dwarfs decreases with increasing age, and the form of the decline depends on SpT. Using the compiled sample of age calibrators, we find that H{alpha} EW and fractional H{alpha} luminosity (L_H{alpha}_/L_bol_) decrease with increasing age. H{alpha}EW for SpT<~M7 decreases gradually up until ~1Gyr. For older ages, we found only two early M dwarfs that are both inactive and seem to continue the gradual decrease. We also found 14 mid-type M-dwarfs, out of which 11 are inactive and present a significant decrease in H{alpha}EW, suggesting that the magnetic activity decreases rapidly after ~1Gyr. We fit L_H{alpha}_/L_bol_ versus age with a broken power law and find an index of -0.11_-0.01_^+0.02^ for ages <~776Myr. The index becomes much steeper at older ages, but a lack of field age-calibrators (>>1Gyr) leaves this part of the relation far less constrained. Finally, from repeated independent measurements for the same stars, we find that 94% of them have a level of H{alpha}EW variability <~5{AA} at young ages (<1Gyr).
269. Sc, V, Mn, and Co in Milky Way stars
ID:
ivo://CDS.VizieR/J/A+A/577/A9
Title:
Sc, V, Mn, and Co in Milky Way stars
Short Name:
J/A+A/577/A9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the elemental abundances of a large sample of F and G dwarfs in the solar neighborhood. The analysis is based on high-resolution spectra obtained with MIKE on the Magellan telescope, FEROS on the ESO 1.5m and 2.2m telescopes, HARPS on the ESO 3.6m telescope, UVES on the ESO Very Large Telescope, SOFIN and FIES on the Nordic Optical Telescope. We focused our study on odd-Z iron-peak elements Sc, V, Mn and Co. Our results show that Sc, V, and Co present similar trend as the alpha elements and in Co case, this is true also when non-local thermodynamic equilibrium corrections (non-LTE, NLTE) are applied. On the contrary Mn is generally underabundant relative the Sun but when NLTE corrections are applied the trend is basically flat with [Mn/Fe]=0. Considering the age as selection criterion for thin and thick disk we did not find any difference for V, Co, and Mn LTE while for Sc and Mn NLTE a small difference seem to be present. Comparisons with the alpha-element Ti show flat trends for all the elements except Mn that present well separated [Mn/Ti]-[Ti/H] for thin and thick disk.
270. SDSS DR7 M dwarfs
ID:
ivo://CDS.VizieR/J/AJ/141/97
Title:
SDSS DR7 M dwarfs
Short Name:
J/AJ/141/97
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectroscopic catalog of 70,841 visually inspected M dwarfs from the seventh data release of the Sloan Digital Sky Survey. For each spectrum, we provide measurements of the spectral type, a number of molecular band heads, and the H{alpha}, H{beta}, H{gamma}, H{delta}, and CaII-K emission lines. In addition, we calculate the metallicity-sensitive parameter {zeta} and identify a relationship between {zeta} and the g-r and r-z colors of M dwarfs. We assess the precision of our spectral types (which were assigned by individual examination), review the bulk attributes of the sample, and examine the magnetic activity properties of M dwarfs, in particular those traced by the higher order Balmer transitions. Our catalog is cross-matched to 2MASS infrared data, and contains photometric distances for each star. Finally, we identify eight new late-type M dwarfs that are possibly within 25 pc of the Sun. Future studies will use these data to thoroughly examine magnetic activity and kinematics in late-type M dwarfs and examine the chemical and dynamical history of the local Milky Way.

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