Related papers: Benchmark cool companions: Ages and abundances for…
In 2010 a sub-stellar companion to the solar analog pre-main sequence star PZ Tel and member of the about 12 Myr old Beta Pic moving group was found by high-contrast direct imaging independently by two teams. In order to determine the basic…
We report the discovery of a tight substellar companion to the young solar analog PZ Tel, a member of the Beta Pictoris moving group observed with high contrast adaptive optics imaging as part of the Gemini NICI Planet-Finding Campaign. The…
Aims: We study the formation of substellar objects (exoplanets and brown dwarfs) as companions to young nearby stars. Methods: With high contrast AO imaging obtained with NACO at ESO's VLT we search for faint companion-candidates around our…
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.…
Dynamical masses of giant planets and brown dwarfs are critical tools for empirically validating substellar evolutionary models and their underlying assumptions. We present a measurement of the dynamical mass and an updated orbit of PZ Tel…
We present updated stellar population models appropriate for old ages (>1 Gyr) and covering a wide range in metallicities (-1.5<[Fe/H]<0.3). These models predict the full spectral variation associated with individual element abundance…
The primary objective of this study is to accurately determine the abundances of Cu, Sr, Y, Zr, Ba, La, and Ce in selected solar-type stars. This will allow us to establish observational abundance-metallicity and abundance-age relations and…
HARPS spectra with signal-to-noise ratios S/N > 600 at 6000 A were analysed with MARCS model atmospheres to obtain 1D LTE abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Sr, and Y for 72 nearby solar-type stars with metallicities in…
HARPS-N spectra with S/N > 250 and MARCS model atmospheres were used to derive abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, and Y in ten stars from the Kepler LEGACY sample (including the binary pair 16 Cyg A and B) selected…
We present our chemical abundance investigation of the metal-poor ([Fe/H]=-1.60 dex), r-process-enriched ([Eu/Fe]=0.73 dex) halo star HD 20 using novel and archival high-resolution spectra at outstanding signal-to-noise ratios. By combining…
Young populations at Z<Zo are being examined to understand the role of metallicity in the first phases of stellar evolution. For the analysis it is necessary to assign mass and age to Pre--Main Sequence (PMS) stars. While it is well known…
H$\alpha$ is a powerful tracer of accretion and chromospheric activity, which has been detected in the case of young brown dwarfs and even recently in planetary mass companions (e.g. PDS70 b and c). H$\alpha$ detections and characterisation…
We have carried out a high resolution spectroscopic survey of the 220-250 Myr old cluster NGC 6475: our main purpose is to investigate Li evolution during the early stages of the Main Sequence. We have determined Li abundances for 33 late F…
[Abridged] Context. The young systems PZ Tel and HD 1160, hosting known low-mass companions, were observed during the commissioning of the new planet finder SPHERE with several imaging and spectroscopic modes. Aims. We aim to refine the…
We present observations of the Be II 313.0 nm resonance doublet in 14 halo and old disk stars with metallicities ranging from [Fe/H]=-0.4 to about -3.0 obtained with the CASPEC spectrograph of the ESO 3.6m telescope at a FWHM about 8.6 km/s…
Despite the extensive study of lithium depletion during pre-main-sequence contraction, studies of individual stars show discrepancies between ages determined from the HR diagram and ages determined from lithium depletion (Song et al. 2002,…
One of the most important factors in determining the stellar lithium abundance is the effective temperature. In a previous study by the authors, new effective temperatures Teff for sixteen metal-poor halo dwarfs were derived using a local…
We present equivalent widths, improved model atmosphere parameters, and revised abundances for 14 species of 11 elements derived from high resolution optical spectroscopy of 311 metal-poor stars. All of these stars had their parameters…
In the search of a sample of metal-poor bright giants using Str{\"o}mgren photometry, we serendipitously found a sample of 26 young (ages younger than 1 Gyr) metal-rich giants, some of which have high rotational velocities.We determined the…
We want to determine the lithium abundances of solar twin stars as a function of stellar age to provide constraints for stellar evolutions models and to investigate whether there is a connection between low Li abundance and the occurrence…