Related papers: Lithium Depletion Boundary in a Pre-Main Sequence …
By collecting optical and infrared photometry, as well as medium resolution spectroscopy, we have discovered a sample of low mass stars and brwon dwarfs in the young cluster IC2391. Using the lithium depletion boundary near the substellar…
The timescale of cluster formation is an essential parameter in order to understand the formation process of star clusters. Pre-main sequence (PMS) stars in nearby young open clusters reveal a large spread in brightness. If the spread were…
Methods. We used the HIRES spectrograph on the Keck I telescope to acquire high-resolution (R $\approx$ 70000) spectra with a high signal-to-noise ratio (S/N $\approx$ 400 - 650 per pixel) of HIP 100963 and the Sun for a differential…
The lithium abundance in turnoff stars of the old population of our Galaxy is remarkably constant in the metallicity interval -2.8\textless{}[Fe/H] \textless{}-2.0, defining a plateau. The Li abundance of these turnoff stars is clearly…
We fit the upper main sequence of the Praesepe and Hyades open clusters using stellar models with and without rotation. When neglecting rotation, we find that no single isochrone can fit the entire upper main sequence at the clusters'…
The z_abs = 2.504 Lyman Limit absorption system (LLS) towards Q1009+2956 has previously been used to estimate the primordial deuterium abundance. Since the initial measurement by Burles & Tytler, this quasar has been observed extensively…
As one of the primordial radioactive isotopes, $^{232}$Th mainly undergoes $\alpha$-decay with a half-life of $1.402 \times 10^{10}$ yr. However, it is also one of 35 double beta decay candidates in which the single $\beta$-decay is…
The lithium present in the photospheres of solar-type stars is transported to the inner parts by convection, reaching regions even somewhat below the convection zone, by non-standard transport mechanisms. In stars with deeper convective…
We present the initial results of a study of the surface lithium abundance in a sample of low-mass members (M~0.4-1.0 Msun) of the Orion Nebula Cluster (ONC) that provide an independent clock to estimate stellar ages. We report discovery of…
The evolution of lithium abundance over a star's lifetime is indicative of transport processes operating in the stellar interior. We revisit the relationship between lithium content and rotation rate previously reported for cool dwarfs in…
We evaluated the bias and variability on the fitted age and convective core overshooting parameter for evolved binary stars accounting for observational and internal uncertainties. We considered a binary system composed of a 2.50 $M_{\sun}$…
In near-infrared NaCo observations of the young brown dwarf 2MASS J0041353-562112, we discovered a companion a little less than a magnitude fainter than the primary. The binary candidate has a separation of 143 mas, the spectral types are…
We present intermediate- and low-resolution optical spectra around Halpha and LiI 6708 A for a sample of 25 low mass stars and 2 brown dwarfs with confirmed membership in the pre-main sequence stellar sigma Orionis cluster. Our observations…
We present the first systematic study of lithium abundance in a chemically homogeneous sample of 27 red supergiants (RSGs) in the young Perseus complex. For these stars, accurate stellar parameters and detailed chemical abundances of iron…
The cosmological Li problem is the observed discrepancy between Li abundance, A(Li), measured in Galactic dwarf, old and metal-poor stars (traditionally assumed to be equal to the initial value A(Li)_0), and that predicted by standard Big…
I review basic observational features in Population I stars which strongly implicate rotation as a mixing agent; these include dispersion at fixed temperature in coeval populations and main sequence lithium depletion for a range of masses…
We report the discovery of a further line of sight allowing detection of HeII Ly alpha absorption by the intergalactic medium. A HST/STIS survey of 32 bright z ~ 3 quasars selected from the Hamburg Quasar Surveys yielded one detection…
Lithium abundances, radial velocities and rotational velocities are reported for 20 candidate F, G and K stars of the sparse Coma Berenices open cluster. All the stars are proper-motion selected, and our radial velocities support the…
We compare the properties of recent samples of the lithium abundances in halo stars to one another and to the predictions of theoretical models including rotational mixing, and we examine the data for trends with metal abundance. We find…
Lithium is one of the few elements produced during the Big Bang Nucleosynthesis in the early universe. Moreover, its fragility makes it useful as a proxy for stellar environmental conditions. As such, the lithium abundance in old systems is…