A detailed study of lithium in 107 CHEPS dwarf stars

Abstract

Context. We report results from lithium abundance determinations using high resolution spectral analysis of the 107 metal-rich stars from the Calan-Hertfordshire Extrasolar Planet Search programme. Aims. We aim to set out to understand the lithium distribution of the population of stars taken from this survey. Methods. The lithium abundance taking account of non-local thermodynamical equilibrium effects was determined from the fits to the Li I 6708 Å resonance doublet profiles in the observed spectra. Results. We find that a) fast rotators tend to have higher lithium abundances; b) log N(Li) is higher in more massive and hot stars; c) log N(Li) is higher in stars of lower log g; d) stars with the metallicities >0.25 dex do not show the lithium lines in their spectra; e) most of our planet hosts rotate slower; and f) a lower limit of lithium isotopic ratio is 7 Li/ 6 Li > 10 in the atmospheres of two stars with planets (SWP) and two non-SWP stars. Conclusions. Measurable lithium abundances were found in the atmospheres of 45 stars located at distances of 20−170 pc from the Sun, for the other 62 stars the upper limits of log N(Li) were computed. We found well defined dependences of lithium abundances on T eff , V sin i, and less pronounced for the log g. In case of V sin i we see two sequences of stars: with measurable lithium and with the upper limit of log N(Li). About 10% of our targets are known to host planets. Only two SWP have notable lithium abundances, so we found a lower proportion of stars with detectable Li among known planet hosts than among stars without planets. However, given the small sample size of our planet-host sample, our analysis does not show any statistically significant differences in the lithium abundance between SWP and stars without known planets.

High-resolution Spectroscopic Study of Dwarf Stars in the Northern Sky: Lithium, Carbon, and Oxygen Abundances

“…A(Li) is predominantly higher among hotter and more massive stars. This main trend is in agreement with results of previous studies (see, e.g., Ramírez et al 2012;Luck 2017;Bensby & Lind 2018;Fu et al 2018;Pavlenko et al 2018). However, there are stars with the same atmospheric parameters and ages but different lithium abundances.…”

“…A linear regression fit to the area of A(Li) ≥ 2.0 values shows that the slope per 1000 K equals to 0.4 ± 0.1 dex as indicated with the upper solid line in Figure 6. We find that this value is close to the value of 0.45 ± 0.1 dex/1000 K found in the work of local metal-rich stars by Pavlenko et al (2018).…”

“…The A(Li) slope per 1000 K equals to 0.6 ± 0.1. A corresponding slope found by Pavlenko et al (2018) is a bit larger and equals to 0.85 ± 0.18 dex but has a larger error. We divided the stellar sample with A(Li) < 2 in two bins as well.…”

Masses, oxygen, and carbon abundances in CHEPS dwarf stars

“…Lithium is an element of special interest in many aspects of modern astrophysics, see Pavlenko et al (2018) and references therein. Li is a fragile element, theoretical models predict lithium depletion that can be compared to the lithium in the Sun and stars of different ages and metallicities.…”

The Li–age correlation: the Sun is unusually Li deficient for its age

“…They claim that there is an increase in the amount of Li burning, the lower the angular momentum is, thus the presence of planets or solar twins in a binary system should present different amounts of lithium in comparison with single field solar twins with the same stellar parameters and age. This is argued by Israelian et al (2009), Delgado Mena et al (2014 and Zahn (1994), but it is probably a secondary effect that accounts for only a small fraction of the total depletion (Pavlenko et al 2018).…”