BESO échelle spectroscopy of solar-type stars at Cerro Armazones

Yields of rotating stars at solar metallicity

We present a new set of stellar yields obtained from rotating stellar models at solar metallicity covering the massive star range (12–60 M⊙). The stellar models were calculated with the latest version of the Geneva stellar evolution code described in Hirschi et al. (2004). Evolution and nucleosynthesis are in general followed up to silicon burning. The yields of our non–rotating models are cons...

Beryllium anomalies in solar-type field stars

We present a study of beryllium (Be) abundances in a large sample of field solar-type dwarfs and sub-giants spanning a large range of effective temperatures. The Be abundances, computed using a very uniform set of stellar parameters and near-UV spectra obtained with 3 different instruments, are used to study the depletion of this light element. The analysis shows that Be is severely depleted fo...

Low-Mass Companions to Solar-Type Stars

We present preliminary results from a coronagraphic survey of young nearby Sun-like stars using the Palomar and Keck adaptive optics systems. We have targeted 251 solar analogs (F5–K5) at 20–160 pc from the Sun, spanning the 3–3000 Myr age range. The youngest (<500 Myr) ≈100 of these have been imaged with deeper exposures to search for sub-stellar companions. The deep survey is sensitive to bro...

Convective Envelopes in Solar - Type Stars :

Convection in Oblate Solar-Type Stars

We present the first global 3D simulations of thermal convection in the oblate envelopes of rapidly-rotating solar-type stars. This has been achieved by exploiting the capabilities of the new Compressible High-ORder Unstructured Spectral difference (CHORUS) code. We consider rotation rates up to 85% of the critical (breakup) rotation rate, which yields an equatorial radius that is up to 17% lar...