- ID:
- ivo://CDS.VizieR/J/A+A/505/L13
- Title:
- Lithium in globular NGC 6397
- Short Name:
- J/A+A/505/L13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most globular clusters are believed to host a single stellar population. They can thus be considered a good place to study the Spite plateau and to search for possible evolutionary modifications of the Li content. We want to determine the Li content of subgiant (SG) and main sequence (MS) stars of the old, metal-poor globular cluster NGC 6397. This work was aimed not only at studying possible Li abundance variations but also to investigate the cosmological Li discrepancy.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/510/4308
- Title:
- Local main-sequence stars with phot. metallicities
- Short Name:
- J/MNRAS/510/4308
- Date:
- 26 Jan 2022 00:36:57
- Publisher:
- CDS
- Description:
- We present a catalogue of 551214 main-sequence stars in the local (d<2kpc) Galactic thick disk and halo, based on a search of stars with large proper motions (>40.0mas/yr) in the Gaia Early Data Release 3. We derive photometric metallicity calibrated from the colour-luminosity-metallicity distribution of 20047 stars with spectroscopic metallicities, collected from various spectroscopic surveys, including SDSS SEGUE/APOGEE, GALAH DR3, and LAMOST DR6. We combine these results to construct an empirical colour- magnitude-metallicity grid, which can be used to estimate photometric metallicities for low-mass metal-poor stars of K and M subtypes from their absolute G magnitude and colour values. We find that low-mass, high-velocity stars in our catalogue share similar kinematics as reported in recent studies of more luminous Galactic halo stars. The pseudo-kinematic analysis of our sample recovers the main local halo structures, including the Gaia-Enceladus Stream and the Helmi stream; aside from these the local halo stars appear to show a remarkably smooth distribution in velocity space. Since the future Gaia data release will provide radial velocity measurements for only a small number of our sample, our catalogue provides targets of high interest for the future spectroscopic observation programs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/373/13
- Title:
- Lower main-sequence stars fundamental param.
- Short Name:
- J/MNRAS/373/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive an empirical effective temperature and bolometric luminosity calibration for G and K dwarfs, by applying our own implementation of the Infrared Flux Method to multiband photometry. Our study is based on 104 stars for which we have excellent BV(RI)_C_ JHK_s_ photometry, excellent parallaxes and good metallicities. Colours computed from the most recent synthetic libraries (ATLAS9 and MARCS) are found to be in good agreement with the empirical colours in the optical bands, but some discrepancies still remain in the infrared. Synthetic and empirical bolometric corrections also show fair agreement.
- ID:
- ivo://CDS.VizieR/J/A+A/471/499
- Title:
- Low-mass stars and brown dwarfs in Blanco 1
- Short Name:
- J/A+A/471/499
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a deep wide field optical survey of the young (~100-150Myr) open cluster Blanco 1 to study its low mass population well down into the brown dwarf regime and estimate its mass function over the whole cluster mass range.
- ID:
- ivo://CDS.VizieR/J/ApJ/633/630
- Title:
- Low-mass stars found in CFHTLS
- Short Name:
- J/ApJ/633/630
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present preliminary results of a new quasar survey being undertaken with multicolor optical imaging from the Canada-France-Hawaii Telescope. The current data consist of 3.83deg^2^ of imaging in the i' and z' filters to a 10{sigma} limit of z'<23.35. Near-infrared photometry of 24 candidate 5.7<z<6.4 quasars confirms them all to be low-mass stars, including two T dwarfs and four or five L dwarfs. Photometric estimates of the spectral type of the two T dwarfs are T3 and T6.
- ID:
- ivo://CDS.VizieR/J/AJ/141/52
- Title:
- Low-mass visual companions to nearby G-dwarfs
- Short Name:
- J/AJ/141/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A complete census of wide visual companions to nearby G-dwarf stars can be achieved by selecting candidates from the Two Micron All Sky Survey (2MASS) Point-Source Catalog and checking their status by second-epoch imaging. Such data are obtained for 124 candidates with separations up to 20", 47 of which are shown to be new physical low-mass stellar companions. A list of visual binaries with G-dwarf primaries is produced by combining newly found companions with historical data.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A116
- Title:
- LSPM J2116+0234 and GJ 686 radial velocities
- Short Name:
- J/A+A/627/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although M dwarfs are known for high levels of stellar activity, they are ideal targets for the search of low-mass exoplanets with the radial velocity (RV) method. We report the discovery of a planetary-mass companion around LSPM J2116+0234 (M3.0 V) and confirm the existence of a planet orbiting GJ 686 (BD+18 3421; M1.0 V). The discovery of the planet around LSPM J2116+0234 is based on CARMENES RV observations in the visual and near-infrared channels. We confirm the planet orbiting around GJ 686 by analyzing the RV data spanning over two decades of observations from CARMENES VIS, HARPS-N, HARPS, and HIRES. We find planetary signals at 14.44 and 15.53d in the RV data for LSPM J2116+0234 and GJ 686, respectively. Additionally, the RV, photometric time series, and various spectroscopic indicators show hints of variations of 42 d for LSPM J2116+0234 and 37 d for GJ 686, which we attribute to the stellar rotation periods. The orbital parameters of the planets are modeled with Keplerian fits together with correlated noise from the stellar activity. A mini-Neptune with a minimum mass of 11.8M_{Earth}_ orbits LSPM J2116+0234 producing a RV semi- amplitude of 6.19m/s, while a super-Earth of mass 6.6M_{Earth}_ orbits GJ 686 and produces a RV semi-amplitude of 3.0m/s. Both LSPM J2116+0234 and GJ 686 have planetary companions populating the regime of exoplanets with masses lower than 15M_{Earth}_ and orbital periods <20d.
- ID:
- ivo://CDS.VizieR/J/AJ/133/439
- Title:
- Luminosity function of M7-L8 ultracool dwarfs
- Short Name:
- J/AJ/133/439
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 20pc, volume-limited sample of M7-L8 dwarfs created through spectroscopic follow-up of sources selected from the Two Micron All Sky Survey Second Incremental Release Point Source Catalog. In this paper we present optical spectroscopy of 198 candidate nearby ultracool dwarfs, including 12 late-M and L dwarfs likely to be within 20pc of the Sun and 94 more distant late-type dwarfs. We have also identified five ultracool dwarfs with spectral signatures of low gravity. Combining these data with previous results, we define a sample of 99 ultracool dwarfs in 91 systems within 20pc. These are used to estimate the J- and K-band luminosity functions for dwarfs with optical spectral types between M7 and L8 (10.5<M_J_<15, 9.5<M_Ks_<13). We find a space density of 4.9x10^-3^/pc^3^ for late-M dwarfs (M7-M9.5) and a lower limit of 3.8x10^-3^/pc^3^ for L dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/771/40
- Title:
- Main-sequence A, F, G, and K stars photometry
- Short Name:
- J/ApJ/771/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on CHARA Array measurements, we present the angular diameters of 23 nearby, main-sequence stars, ranging from spectral types A7 to K0, 5 of which are exoplanet host stars. We derive linear radii, effective temperatures, and absolute luminosities of the stars using Hipparcos parallaxes and measured bolometric fluxes. The new data are combined with previously published values to create an Angular Diameter Anthology of measured angular diameters to main-sequence stars (luminosity classes V and IV). This compilation consists of 125 stars with diameter uncertainties of less than 5%, ranging in spectral types from A to M. The large quantity of empirical data is used to derive color-temperature relations to an assortment of color indices in the Johnson (BVR_J_I_J_JHK), Cousins (R_C_I_C_), Kron (R_K_I_K_), Sloan (griz), and WISE (W_3_W_4_) photometric systems. These relations have an average standard deviation of ~3% and are valid for stars with spectral types A0-M4. To derive even more accurate relations for Sun-like stars, we also determined these temperature relations omitting early-type stars (T_eff_>6750K) that may have biased luminosity estimates because of rapid rotation; for this subset the dispersion is only ~2.5%. We find effective temperatures in agreement within a couple of percent for the interferometrically characterized sample of main-sequence stars compared to those derived via the infrared flux method and spectroscopic analysis.
- ID:
- ivo://CDS.VizieR/J/A+A/543/A54
- Title:
- 61 main-sequence and subgiant oscillations
- Short Name:
- J/A+A/543/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Solar-like oscillations have been observed by Kepler and CoRoT in several solar-type stars, thereby providing a way to probe the stars using asteroseismology We provide the mode frequencies of the oscillations of various stars required to perform a comparison with those obtained from stellar modelling. We used a time series of nine months of data for each star. The 61 stars observed were categorised in three groups: simple, F-like, and mixed-mode. The simple group includes stars for which the identification of the mode degree is obvious. The F-like group includes stars for which the identification of the degree is ambiguous. The mixed-mode group includes evolved stars for which the modes do not follow the asymptotic relation of low-degree frequencies. Following this categorisation, the power spectra of the 61 main-sequence and subgiant stars were analysed using both maximum likelihood estimators and Bayesian estimators, providing individual mode characteristics such as frequencies, linewidths, and mode heights. We developed and describe a methodology for extracting a single set of mode frequencies from multiple sets derived by different methods and individual scientists. We report on how one can assess the quality of the fitted parameters using the likelihood ratio test and the posterior probabilities. We provide the mode frequencies of 61 stars (with their 1-{sigma} error bars), as well as their associated echelle diagrams.
