THE HYADES CLUSTER: IDENTIFICATION OF A PLANETARY SYSTEM AND ESCAPING WHITE DWARFS
THE HYADES CLUSTER: IDENTIFICATION OF A PLANETARY SYSTEM AND ESCAPING WHITE DWARFS
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毕星团：行星系统的识别和逃逸的白矮星
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
M. Jura
中科院分区：
文献类型：
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作者：
B. Zuckerman;Siyi Xu;B. Klein;M. Jura
最近，一些热的DA型白色矮星被认为可能是毕宿星团的逃逸成员。我们用氢的巴耳末线来测量七颗这样的恒星的径向速度，并确认其中三颗，也许还有另外两颗，确实是星团成员，而一颗不是。另一个候选人Hyad具有很强的吸引力，其成员地位仍然不确定。至少四分之一的场白色矮星的光球被吸积的比氦重的元素“污染”。这些恒星的轨道是由扩展的行星系统，其中包括碎片带和主要行星。我们观测了七颗经典的毕宿单白色矮星和新发现的（逃逸的）毕宿白色矮星，并在DBA型（现在的DBAZ）LP 475-242的光球层中发现了钙，这意味着存在一个轨道行星系统。白色矮星GD 31可能是毕宿星团的逃逸成员，但也可能不是，它的光谱显示出钙的吸收线;这些吸收线要么来自星际介质，要么来自气态的星周盘。如果GD 31曾经是毕宿星的成员，那么它将是第一个被确认的白色矮星毕宿星，冷却年龄超过3.4亿年。
Recently, some hot DA-type white dwarfs have been proposed to plausibly be escaping members of the Hyades. We used hydrogen Balmer lines to measure the radial velocities of seven such stars and confirm that three, and perhaps two others, are/were indeed cluster members and one is not. The other candidate Hyad is strongly magnetic and its membership status remains uncertain. The photospheres of at least one quarter of field white dwarf stars are “polluted” by elements heavier than helium that have been accreted. These stars are orbited by extended planetary systems that contain both debris belts and major planets. We surveyed the seven classical single Hyades white dwarfs and the newly identified (escaping) Hyades white dwarfs and found calcium in the photosphere of LP 475-242 of type DBA (now DBAZ), thus implying the presence of an orbiting planetary system. The spectrum of white dwarf GD 31, which may be, but probably is not, an escaping member of the Hyades, displays calcium absorption lines; these originate either from the interstellar medium or, less likely, from a gaseous circumstellar disk. If GD 31 was once a Hyades member, then it would be the first identified white dwarf Hyad with a cooling age >340 Myr.