A selection of hot subluminous stars in the GALEX survey II. Subdwarf atmospheric parameters

TL;DR

This study updates the atmospheric parameters of hot subdwarf stars from the GALEX survey using spectroscopic analysis, revealing their compositions, binary companions, and stellar classifications.

Contribution

It provides a comprehensive spectroscopic analysis of 180 hot subdwarfs, including binary decomposition and abundance measurements, enhancing understanding of their properties.

Findings

Identified 124 sdB and 42 sdO stars.

Analyzed binary companions in 29 systems.

Improved estimates of T_eff, log g, and elemental abundances.

Abstract

We present an update of our low-resolution spectroscopic follow-up and model atmosphere analysis of hot subdwarf stars from the Galaxy Evolution Explorer (GALEX) survey. Targets were selected on the basis of colour indices calculated from the GALEX GR6 N_UV, Guide Star Catalogue (GSC2.3.2) V and the Two Micron All Sky Survey (2MASS) J and H photometry. High signal-to-noise ratio spectra were obtained at the European Southern Observatory (ESO) and the Kitt Peak National Observatory (KPNO) over the course of three years. Detailed H, He and CNO abundance analysis helped us improve our T_eff, log g and He abundance determination and to constrain CNO abundances. We processed 191 observations of 180 targets and found 124 sdB and 42 sdO stars in this sample while some blue horizontal branch stars were also found in this programme. With quantitative binary decomposition of 29 composite spectra we investigated the incidence of A, F and G type companions. The incidence of late G and K type companions and their effects on subdwarf atmospheric parameters were also examined.