Stellar Spectra and Atmospheric Composition

Estimation of stellar atmospheric parameters from SDSS/SEGUE spectra

We present techniques for the estimation of stellar atmospheric parameters (Teff , log g, [Fe/H]) for stars from the SDSS/SEGUE survey. The atmospheric parameters are derived from the observed medium-resolution (R = 2000) stellar spectra using non-linear regression models trained either on (1) pre-classified observed data or (2) synthetic stellar spectra. In the first case we use our models to ...

Atmospheric Structure and Composition,

Automated analysis of stellar spectra

Classical model-atmosphere analyses of stellar spectra usually begin by measuring equivalent widths, and then proceed into a loop in which 1) model spectra are calculated for a set of abundances and atmospheric parameters, and 2) observed and computed spectra are compared and corrections to the abundances and parameters are inferred. Automated techniques have been developed to automate the meas...

Stellar Rotation from GAIA Spectra

Abstract. Stellar rotation influences our understanding of stellar structure and evolution, binary systems, clusters etc. and therefore the benefits of a large and highly accurate database on stellar rotation, obtained by GAIA, will be manifold. To study the prospects of GAIA measurement of projected rotational velocities vrot sin i, we use synthetic stellar spectra to simulate the determinatio...

Atmospheric Composition, Chemistry, and Clouds

Venus’ atmosphere has a rich chemistry involving interactions among sulfur, chlorine, nitrogen, hydrogen, and oxygen radicals. The chemical regimes in the atmosphere range from ion-neutral reactions in the ionosphere to photochemistry in the middle atmosphere to thermal equilibrium chemistry and surface-atmosphere reactions in the lower atmosphere. This variety makes Venus an important planet t...