标题： 富含氦的炙热次矮星的SALT巡天：方法、分类和粗略分析 显示英文标题

标题： The SALT survey of helium-rich hot subdwarfs: methods, classification, and coarse analysis

摘要： 使用南非大望远镜（SALT）正在进行一项关于氦丰富的炽热次矮星的中高分辨率光谱巡天。目标包括发现奇异的炽热次矮星以及连接不同类型的化学异常次矮星序列。第一阶段包括对从低分辨率巡天中选出的超过100颗恒星进行中等分辨率光谱观测。本文描述了选择标准以及观测、分类和分析方法。它给出了基于MK类似Drilling系统的107个光谱分类，并且基于零金属非LTE和线填充LTE模型大气网格的混合格架进行了106个粗略分析（$T_{\rm eff}, \log g, \log y$）。对于75颗恒星，首次得出了大气参数。样本可以分为6个不同的组，包括经典的“富氦”sdO星（光谱类型sdO6.5 - sdB1，共74颗），其中包括碳丰富（35颗）和碳弱（39颗）星；非常热的He-sdO星（光谱类型$\lesssim$sdO6，共13颗）；光度等级为$\lesssim 5$的极端氦星（5颗）；氦类别25 - 35的中间氦丰富次矮星（8颗）；以及氦类别$10 - 25$的中间氦丰富次矮星（6颗）。最后一组涵盖了一个狭窄的光谱范围（sdB0 - sdB1），其中包括两颗已知的和四颗候选的重元素次矮星。在其他组中还有一些个别感兴趣的恒星，包括一颗极度金属贫乏的氦星、候选双氦次矮星双星系统以及一颗候选低重力He-sdO星。 显示英文摘要

摘要： A medium- and high-resolution spectroscopic survey of helium-rich hot subdwarfs is being carried out using the Southern African Large Telescope (SALT). Objectives include the discovery of exotic hot subdwarfs and of sequences connecting chemically-peculiar subdwarfs of different types. The first phase consists of medium-resolution spectroscopy of over 100 stars selected from low-resolution surveys. This paper describes the selection criteria, and the observing, classification and analysis methods. It presents 107 spectral classifications on the MK-like Drilling system and 106 coarse analyses ($T_{\rm eff}, \log g, \log y$) based on a hybrid grid of zero-metal non-LTE and line-blanketed LTE model atmospheres. For 75 stars, atmospheric parameters have been derived for the first time. The sample may be divided into 6 distinct groups including the classical `helium-rich' sdO stars with spectral types (Sp) sdO6.5 - sdB1 (74) comprising carbon-rich (35) and carbon-weak (39) stars, very hot He-sdO's with Sp $\lesssim$ sdO6 (13), extreme helium stars with luminosity class $\lesssim 5$ (5), intermediate helium-rich subdwarfs with helium class 25 -- 35 (8), and intermediate helium-rich subdwarfs with helium class $10 - 25$ (6). The last covers a narrow spectral range (sdB0 -- sdB1) including two known and four candidate heavy-metal subdwarfs. Within other groups are several stars of individual interest, including an extremely metal-poor helium star, candidate double-helium subdwarf binaries, and a candidate low-gravity He-sdO star.