Chemically Peculiar Hot Subdwarfs

摘要：热亚矮星代表了一种罕见但寿命相对较长的恒星，现在被GAIA明确地识别为赫茨普龙-罗素图中的一个独特类别。它们中的大多数都有富氢的表面，可以解释为核心-氦燃烧的恒星，它们在密切的双星相互作用中失去了大部分的表面层。大约10 - 20%的岩石表面富含氦气，而且一定来自其他演化通道。我们正在用SALT和LAMOST对这些恒星进行光谱调查，并发现了各种各样的奇异物体，包括重金属亚矮星、逃逸恒星、极端星族II星和新的极端氦星。该学生将接管SALT巡天数据的日常操作和简化，并将学习光谱分析技术来检查单个恒星，以便对恒星演化的后期阶段做出更全面的贡献。

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.