- ID:
- ivo://CDS.VizieR/J/MNRAS/451/4368
- Title:
- Lithium abundance of solar-like stars
- Short Name:
- J/MNRAS/451/4368
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the determination of the lithium abundance [A(Li)] of 52 solar-like stars. For 41 objects the A(Li) here presented corresponds to the first measurement. We have measured the equivalent widths of the 6708 {AA} lithium feature in high-resolution spectroscopic images (R~80000), obtained at the Observatorio Astrofisico Guillermo Haro (Sonora, Mexico), as part of the first scientific observations of the revitalized Lunar and Planetary Laboratory (LPL) Echelle Spectrograph, now known as the Cananea High-resolution Spectrograph (CanHiS). Lithium abundances were derived with the Fortran code MOOG, using as fundamental input a set of atmospheric parameters recently obtained by our group. With the help of an additional small sample with previous A(Li) determinations, we demonstrate that our lithium abundances are in agreement, to within uncertainties, with other works. Two target objects stand out from the rest of the sample. The star BD+47 3218 (T_eff_=6050+/-52 K, A(Li)=1.86+/-0.07 dex) lies inside the so-called lithium desert in the A(Li)-T_eff_ plane. The other object, BD+28 4515, has an A(Li)=3.05+/-0.07 dex, which is the highest of our sample and compatible with the expected abundances of relatively young stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/615/A151
- Title:
- Lithium abundances in 714 F and G dwarf stars
- Short Name:
- J/A+A/615/A151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a detailed analysis of Li in 714 nearby dwarf stars. Li abundances were determined through spectral line synthesis of the Li feature at 670.8 nm. The stellar sample traces the evolution of the Galactic thin and thick disks in the solar neighbourhood, and is the same as previously analysed by Bensby et al. (2014, Cat. J/A+A/562/A71) where stellar parameters and ages were taken from. The same sample was also used in Battistini & Bensby (2015, Cat. J/A+A/577/A9, 2016, Cat. J/A+A/586/A49) wherein abundances for odd iron-peak elements and r- and s-process elements can be found.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/46
- Title:
- Lithium abundances in HIP stars
- Short Name:
- J/ApJ/756/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive atmospheric parameters and lithium abundances for 671 stars and include our measurements in a literature compilation of 1381 dwarf and subgiant stars. First, a "lithium desert" in the effective temperature (T_eff_) versus lithium abundance (A_Li_) plane is observed such that no stars with T_eff_=~6075K and A_Li_=~1.8 are found. We speculate that most of the stars on the low A_Li_ side of the desert have experienced a short-lived period of severe surface lithium destruction as main-sequence or subgiant stars. Next, we search for differences in the lithium content of thin-disk and thick-disk stars, but we find that internal processes have erased from the stellar photospheres their possibly different histories of lithium enrichment. Nevertheless, we note that the maximum lithium abundance of thick-disk stars is nearly constant from [Fe/H]=-1.0 to -0.1, at a value that is similar to that measured in very metal-poor halo stars (A_Li_=~2.2). Finally, differences in the lithium abundance distribution of known planet-host stars relative to otherwise ordinary stars appear when restricting the samples to narrow ranges of T_eff_ or mass, but they are fully explained by age and metallicity biases. We confirm the lack of a connection between low lithium abundance and planets. However, we find that no low A_Li_ planet-hosts are found in the desert T_eff_ window. Provided that subtle sample biases are not responsible for this observation, this suggests that the presence of gas giant planets inhibit the mechanism responsible for the lithium desert.
- ID:
- ivo://CDS.VizieR/J/A+A/634/A130
- Title:
- Lithium abundances in microlensed bulge dwarfs
- Short Name:
- J/A+A/634/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lithium abundances are presented for 91 dwarf and subgiant stars in the Galactic bulge. The analysis is based on line synthesis of the ^7^Li line at 6707{AA} in high-resolution spectra obtained during gravitational microlensing events, when the brightnesses of the targets were highly magnified. Our main finding is that bulge stars at sub-solar metallicities that are older than about eight billion years do not show any sign of Li production; that is, the Li trend with metallicity is flat or even slightly declining. This indicates that no lithium was produced during the first few billion years in the history of the bulge. This finding is essentially identical to what is seen for the (old) thick disk stars in the solar neighbourhood, and adds another piece of evidence for a tight connection between the metal-poor bulge and the Galactic thick disk. For the bulge stars younger than about eight billion years, the sample contains a group of stars at very high metallicities at [Fe/H]~=+0.4 that have lithium abundances in the range A(Li)=2.6-2.8. In the solar neighbourhood the lithium abundances have been found to peak at A(Li)~=3.3 at [Fe/H]~=+0.1 and then decrease by 0.4-0.5dex when reaching [Fe/H]~=+0.4. The few bulge stars that we have at these metallicities seem to support this declining A(Li) trend. This could indeed support the recent claim that the low A(Li) abundances at the highest metallicities seen in the solar neighbourhood could be due to stars from the inner disk, or the bulge region, that have migrated to the solar neighbourhood.
- ID:
- ivo://CDS.VizieR/J/ApJ/785/94
- Title:
- Lithium abundances of a large sample of red giants
- Short Name:
- J/ApJ/785/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The lithium abundances for 378 G/K giants are derived with non-local thermodynamic equilibrium correction considered. Among these are 23 stars that host planetary systems. The lithium abundance is investigated, as a function of metallicity, effective temperature, and rotational velocity, as well as the impact of a giant planet on G/K giants. The results show that the lithium abundance is a function of metallicity and effective temperature. The lithium abundance has no correlation with rotational velocity at v sin i<10 km/s. Giants with planets present lower lithium abundance and slow rotational velocity (v sin i<4 km/s). Our sample includes three Li-rich G/K giants, 36 Li-normal stars, and 339 Li-depleted stars. The fraction of Li-rich stars in this sample agrees with the general rate of less than 1% in the literature, and the stars that show normal amounts of Li are supposed to possess the same abundance at the current interstellar medium. For the Li-depleted giants, Li-deficiency may have already taken place at the main sequence stage for many intermediate mass (1.5-5 M_{sun}_)G/K giants. Finally, we present the lithium abundance and kinematic parameters for an enlarged sample of 565 giants using a compilation of the literature, and confirm that the lithium abundance is a function of metallicity and effective temperature. With the enlarged sample, we investigate the differences between the lithium abundance in thin-/thick-disk giants, which indicate that the lithium abundance in thick-disk giants is more depleted than that in thin-disk giants.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/116
- Title:
- Long-term variability of Kepler sun-like stars
- Short Name:
- J/ApJ/851/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry from the Kepler mission is optimized to detect small, short- duration signals like planet transits at the expense of long-term trends. This long-term variability can be recovered in photometry from the full-frame images (FFIs), a set of calibration data collected approximately monthly during the Kepler mission. Here we present f3, an open-source package to perform photometry on the Kepler FFIs in order to detect changes in the brightness of stars in the Kepler field of view over long time baselines. We apply this package to a sample of 4000 Sun-like stars with measured rotation periods. We find that ~10% of these targets have long-term variability in their observed flux. For the majority of targets, we find that the luminosity variations are either correlated or anticorrelated with the short-term variability due to starspots on the stellar surface. We find a transition between anticorrelated (starspot-dominated) variability and correlated (facula-dominated) variability between rotation periods of 15 and 25 days, suggesting the transition between the two modes is complete for stars at the age of the Sun. We also identify a sample of stars with apparently complete cycles, as well as a collection of short-period binaries with extreme photometric variation over the Kepler mission.
- 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/511/A54
- Title:
- Magnetic cycles and radial-velocity for 8 stars
- Short Name:
- J/A+A/511/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ever increasing level of precision achieved by present and future radial velocity instruments is opening the way to the discovery of very low mass, long period planets (e.g. solar-system analogs). These systems will be detectable as low amplitude signals in radial-velocity (RV). However, an important obstacle to their detection may be the existence of stellar magnetic cycles with similar timescales. Here we present the results of a long term program to measure simultaneously radial-velocities and stellar activity indicators (CaII, H{alpha}, HeI) for a sample of stars with known activity cycles. Our results suggest that all these stellar activity indexes can be used to trace the stellar magnetic cycle in solar-type stars. Further to this, we find clear indications that different parameters of the HARPS cross-correlation function (BIS, FWHM, and Contrast) are also sensitive to activity level variations. Finally, we show that though in a few cases slight correlations or anti-correlations between radial-velocity and the activity level of the star exist, their origin is still not clear. We can however conclude that for our targets (early-K dwarfs) we do not find evidence for radial-velocity variations induced by variations of the stellar magnetic cycle with amplitudes significantly above 1m/s.
- ID:
- ivo://CDS.VizieR/J/MNRAS/441/2316
- Title:
- 10 nearby solar-type dwarfs RV curves
- Short Name:
- J/MNRAS/441/2316
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Several nearby solar-type dwarfs with variable radial velocity were monitored to find their spectroscopic orbits. Orbital elements of HIP 179, 1989, 2981, 5276, 6439, 11218, 21443, 96434 are determined, as well as tentative orbits for HIP 28678 and 41214. We discuss each of those objects. Three of the four double-lined binaries are twins with nearly equal components. All four orbits with periods shorter than 10d are circular, the remaining orbits are eccentric.
- ID:
- ivo://CDS.VizieR/J/A+A/576/A89
- Title:
- O abundances from HARPS in F-G stars
- Short Name:
- J/A+A/576/A89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed and uniform study of oxygen abundance from two different oxygen lines at 6158{AA} and 6300{AA} in a large sample of solar-type stars. The results are used to check the behaviour of these spectral lines as oxygen abundance indicators and to study the evolution of oxygen in thick and thin disk populations of the Galaxy. Equivalent width measurements were carried out for the [OI]6158 and [OI]6300 lines. LTE abundances were obtained from these two lines in 610 and 535 stars, respectively. Careful error analysis has been performed.
