相关论文: Lithium Depletion Boundary in a Pre-Main Sequence …

Old open clusters are very useful targets to investigate mechanisms responsible for lithium (Li) depletion during the main sequence. Comparison of the Li abundances in clusters of different age allows us to understand the efficiency of the…

We present the results of a spectroscopic survey of X-ray selected, low-mass candidate members of the young open cluster NGC 2547. Using a combination of photometry, spectroscopic indices and radial velocities we refine our candidate list…

We identify 6 early M-dwarfs, in 3 open clusters (NGC 2451a, Blanco 1 and NGC 2516) at ages of 50-200 Myr, that are anomalously enriched in lithium compared with Li-depleted siblings of similar spectral type. The Li-rich outliers represent…

We present a study of the lithium abundances of a sample of evolved components of Chromospherically Active Binary Systems. We show that a significant part of them have lithium excesses, independently of their mass and evolutionary stage.…

We mainly aim to search for the lithium depletion boundary (LDB) among the sub-stellar population of the open star cluster Coma Berenices. We carried out a search for brown dwarf (BD) candidates using colour-magnitude diagrams combining…

We present the discovery of an object in the Pleiades open cluster, named Teide 2, with optical and infrared photometry which place it on the cluster sequence slightly below the expected substellar mass limit. We have obtained low- and…

Late M-type dwarfs in the solar neighborhood include a mixture of very low-mass stars and brown dwarfs which is difficult to disentangle due to the lack of constraints on their age such as trigonometric parallax, lithium detection and space…

We want to study the effects of the formation of planets and planetary systems on the atmospheric Li abundance of planet host stars. In this work we present new determinations of lithium abundances for 326 Main Sequence stars with and…

Lithium is an excellent tracer of mixing in stars as it is destroyed (by nuclear reactions) at a temperature around $\sim 2.5\times 10^6$ K. The lithium destruction zone is typically located in the radiative region of a star. If the…

In a coeval group of low-mass stars, the luminosity of the sharp transition between stars that retain their initial lithium and those at slightly higher masses in which Li has been depleted by nuclear reactions, the lithium depletion…

We report a late M-type, common proper motion companion to a nearby young visual binary HIP 115147 (V368 Cep), separated by 963 arcseconds from the primary K0 dwarf. This optically dim star has been identified as a candidate high proper…

We present Li abundances for 73 stars in the metallicity range -3.5 < [Fe/H] < -1.0 using improved IRFM temperatures (Casagrande et al. 2010) with precise E(B-V) values obtained mostly from interstellar NaI D lines, and high-quality…

Our study is a follow-up of the SACY project, an extended survey in the Southern Hemisphere targeted to search for young nearby associations. Nine associations have either been newly identified, or had their member list better defined.…

We present Keck I/OSIRIS and Keck II/NIRC2 adaptive optics imaging of two member candidates of the Praesepe stellar cluster (d=186.18$\pm$0.11 pc; 590-790 Myr), UGC J08451066+2148171 (L1.5$\pm$0.5) and UGCS J08301935$+$2003293 (no…

The current status of observational studies of lithium depletion in open clusters is reviewed, concentrating mainly on G and K type stars. I attempt to answer the following questions: Can the lithium depletion patterns seen in open clusters…

We present the first detailed chemical abundance analysis of the old 8.2 Gyr solar twin, HIP 102152. We derive differential abundances of 21 elements relative to the Sun with precisions as high as 0.004 dex ($\lesssim$1%), using ultra…

We present lithium abundances for ~50 X-ray selected candidate members of the 30-50 Myr old open clusters IC 2602 and IC 2391. These data enlarge and extend to cooler temperatures previous Li surveys of these clusters by Stauffer et al.…

We utilize spectroscopically derived model atmosphere parameters and the \ion{Li}{1} $\lambda6104$ subordinate line and the $\lambda6708$ doublet to derive lithium abundances for 12 members of the Upper-Centaurus Lupus (UCL) and…

We have obtained intermediate resolution spectra of eleven candidate brown dwarf members of the Pleiades open cluster using the Keck II telescope and LRIS spectrograph. Our primary goal was to determine the location of the "lithium…

To alleviate the discrepancy between the prediction of the primordial lithium abundance in the universe and the abundances observed in Pop II dwarfs and subgiant stars, it has been suggested that the stars observable today have undergone…