Lithium abundances, or upper limits, have been derived for 161 galactic carbon stars, selected from the Two Micron Sky Survey, using high resolution, high signal to noise ratio spectra and synthetic spectrum fitting. Fourteen of these C-stars present surface lithium abundances [log ɛ(Li) ≥ 1.0] higher than theoretically expected during the AGB

Connecting observational data to recent theoretical prescriptions for the luminosity of RR Lyrae, we present a new estimate of the bolometric magnitude of the first brightest red giant for a selected sample of galactic globular clusters. Comparison with theoretical prescriptions for the red giant luminosity at the He-flash discloses an excellent

In a multi-site photometric campaign to monitor T Tauri stars (TTS) in the Taurus-Auriga cloud over more than two months - dubbed Coordinated Observations of Young ObjecTs from Earthbound Sites (COYOTES), we find all 24 of our target stars show evidence for periodic light variations with periods between 1.2 and 24.0 days. This more than doubles the

This thesis falls into the general category of studies of the outer layers of stars on the mid to lower main sequence. It deals specifically with the properties of the convective envelopes of F-type stars, and how these relate to mixing mechanisms in their interiors and energy deposition in their atmospheres. The observational context of the study

We present an analysis of time correlations between measurements of solar radius, neutrino flux data, and acoustic mode frequency shifts. We find significant anticorrelation of the first two quantities with the last one. Variations are found over time scales of order the 11 yr solar cycle and at shorter time scales. The shorter periods, of order 1

Analytical approximations and 2D hydrodynamical simulations are used to examine the interaction of supernova fragments with the internal structure of large multisupernova remnants (MSRs). The fragments are thermalized by reverse shocks generated in the interaction with the MSR interior, which is assumed to be hot and rarefied. The evolution is