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A binary star fraction of 76 per cent and unusual orbit parameters for the blue stragglers of NGC 188

机译：NGC 188的蓝色散流者的76％双星比例和不寻常的轨道参数

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Blue straggler stars lie on or near the main sequences of star clusters (all members of which formed around the same time), but typically are more luminous than the turn-off stars and therefore long ago should have evolved off the main sequence to become giants and white dwarfs. They are thought to derive from normal main-sequence stars that have undergone a recent increase in mass. Statistical evidence indicates that in globular star clusters the blue stragglers probably form from binary stars. The specific formation processes, such as mass transfer, mergers or stellar collisions during dynamical encounters of binary stars, remain unresolved. Here we report that 16 of the 21 blue stragglers (76 per cent) in the old (7-Gyr; ref. 2) open cluster NGC 188 are currently in binary systems, a frequency three times that found among normal solar-type main-sequence stars. These blue straggler binaries have a remarkable period-eccentricity distribution, with all but three having orbital periods of ～1,000 days. Moreover, these stars are rotating faster than normal main-sequence stars of the same surface temperatures. These data show that most, and possibly all, blue stragglers derive from multiple-star systems, and indicate that the several formation processes operate simultaneously. We suggest that rapid rotation of blue stragglers may place upper limits on their ages.
机译：蓝色散乱的恒星位于星团的主要序列上或附近（它们的所有成员大约在同一时间形成），但通常比熄灭的恒星更发光，因此很久以前就应该从主要序列演化而成为巨人和白矮星。它们被认为是来自质量最近增加的正常主序星。统计证据表明，在球状星团中，蓝色散流者可能是由双星形成的。仍未解决特定的形成过程，例如质量转移，合并或双星恒星相遇期间的恒星碰撞。在这里，我们报告说，旧的（7-Gyr；参考文献2）开放星系NGC 188中的21个蓝色散乱者中的16个（占76％）目前处于二进制系统中，该频率是普通太阳能型主星团中的三倍。序列星。这些蓝色的散乱双星具有明显的周期偏心率分布，除了三个以外，其他所有星的轨道周期均为〜1,000天。而且，这些恒星的旋转速度快于表面温度相同的正常主序恒星。这些数据表明，大多数（可能是全部）蓝色散布者来自多星系统，并表明多个形成过程同时进行。我们建议蓝色流浪者的快速旋转可能对其年龄设置上限。

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  • 来源
    《Nature》 |2009年第7276期|1032-1035|共4页
  • 作者

    Robert D. Mathieu; Aaron M. Geller;

  • 作者单位

    Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, Wisconsin 53706, USA;

    Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, Wisconsin 53706, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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  • 正文语种 eng
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