标题： 使用 FUSE 观测 DA 型白矮星寻找双星系统 显示英文标题

标题： A search for binarity using FUSE observations of DAO white dwarfs

摘要： 我们报告了一项针对远紫外光谱探测器（FUSE）观测到的DA型白矮星双星系统的搜寻研究。通过FUSE记录的光谱由多个独立曝光组成。观察曝光之间恒星表面重元素吸收线相对于静止星际介质线的位置变化，可以揭示径向速度的变化——即双星系统存在的证据。该技术成功识别出了样本中16颗白矮星中已知的5颗双星，但对于额外一颗星Ton 320，仅发现了显著的径向速度偏移。该天体也已知存在红外过量辐射。DAO型白矮星大致可分为低质量或正常质量两类。低质量白矮星可能是双星演化形成的，但有研究表明较低质量的DAO可能作为单星从水平分支演化而来，我们在12颗相对低质量的白矮星中未发现双星系统的证据。如果高质 DAO 型白矮星存在于双星系统中，也可以解释它们的存在，但在所研究的四个高质量星体中，尽管PG 1210+533和LB 2没有显示出显著的径向速度偏移，但前者仅有两次曝光，后者存在红外过量辐射。 显示英文摘要

摘要： We report on a search for evidence of binarity in Far-Ultraviolet Spectroscopic Explorer (FUSE) observations of DAO white dwarfs. Spectra recorded by FUSE are built up from a number of separate exposures. Observation of changes in the position of photospheric heavy element absorption lines between exposures, with respect to the stationary interstellar medium lines, would reveal radial velocity changes - evidence of the presence of a binary system. This technique is successful in picking out all the white dwarfs already known to be binaries, which comprise 5 out of the sample of 16, but significant radial velocity shifts were found for only one additional star, Ton 320. This object is also known to have an infrared excess. DAOs can be separated broadly into low or normal mass objects. Low mass white dwarfs can be formed as a result of binary evolution, but it has been suggested that the lower mass DAOs evolve as single stars from the extended horizontal branch, and we find no evidence of binarity for 8 out of the 12 white dwarfs with relatively low mass. The existence of higher mass DAOs can also be explained if they are within binary systems, but of the four higher mass stars in the sample studied, PG 1210+533 and LB 2 do not exhibit significant radial velocity shifts, although there were only two exposures for the former object and the latter has an infrared excess.