1994/02/18 by Ben Dorman, Dorman, Ben, R. W. O’Connell +5
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #Scientific Research and Discoveries #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9402046
To appear in `Hot Stars in the Halo' ed. S.J. Adelman (CUP 1994) (uuencoded compressed Postscript file, 12pp.)
arxiv created 1994/02/18 · openalex publication_date 1994/02/18 · arxiv updated 2009/12/01 · openalex created_date 2021/02/01 · openalex updated_date 2026/07/28
We present the case that populations of sdB/sdOB/sdO-type stars may be a\ncommon constituent of galactic stellar populations, responsible for the UV\nupturn (`UVX') observed in the spectra of spiral bulges and normal galaxy\nnuclei. Extreme Horizontal Branch stars with \log g > 5 and \log teff >\n20,000K have emerged in the last few years as the most likely candidate for\nthe origin of the UVX. The magnitude of this far-UV flux in some systems (e.g.\nNGC~1399, NGC~4649) indicates that galactic nuclear regions must contain larger\nnumbers of these subdwarfs than does the solar neighbourhood. This paper\nsummarizes the results of a quantitative study of the UV radiation from evolved\nstellar populations. We have computed a large grid of stellar models in\nadvanced stages of evolution, as well as a set of isochrones for ages 2-20 Gyr,\nfor a wide range in composition. We use these calculations to derive synthetic\nUV colour indices for stellar populations with hot components.\n