Chemically Peculiar Hot Subdwarfs

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Summary: Hot subdwarfs represent a rare but relatively-long-lived class of star, now clearly identified by GAIA as a distinct class in the Hertzsprung-Russell diagram. The majority have hydrogen-rich surfaces and can be accounted for as core-helium burning stars which lost most of their surface layers in a close binary-star interaction. About 10 - 20 per cent have helium rich surfaces, and must come from other evolution channels. We are carrying out a spectroscopic survey of these stars with SALT and also with LAMOST, and are discovering an extraordinary variety of exotic objects, including heavy-metal subdwarfs, runaway stars, extreme population II stars, and new extreme helium stars. The student will take over the day-to-day operation and reduction of the SALT survey data, and will learn techniques of spectral analysis to examine individual stars, in order to contribute to a more comprehensive picture of the late stages of stellar evolution.