A SPECTROSCOPIC BINARY IN THE HERCULES DWARF SPHEROIDAL GALAXY
A SPECTROSCOPIC BINARY IN THE HERCULES DWARF SPHEROIDAL GALAXY
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DOI：
10.1088/0004-637x/780/1/91
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发表时间：
2013-11
期刊：
影响因子：
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通讯作者：
A. Koch;T. Hansen;S. Feltzing;M. Wilkinson
中科院分区：
文献类型：
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作者：
A. Koch;T. Hansen;S. Feltzing;M. Wilkinson
我们给出了在微弱的大力神矮球(DSph)星系中单线光谱双星的径向速度曲线，基于超过两年的观测的34个单独光谱。这是第一次可以在dSph中为双星推导轨道元素。该系统由一颗贫金属红巨星和一颗可能是白矮星的低质量伴星组成，在中等偏心轨道(e=0.18)上运行135天。它的周期和偏心率与银晕中的贫金属双星完全一致，而投影的半长轴较小，在ap sin i=38R☉。事实上，非常近的轨道可能会通过S过程的核合成抑制较重元素的产生，导致这颗恒星中发现的中子俘获元素的丰度非常低。我们讨论了大力神dSph化学富集史的进一步含义，但没有发现令人信服的双星情景来合理解释大力神dSph星系完整的、特殊的丰度模式。
We present the radial velocity curve of a single-lined spectroscopic binary in the faint Hercules dwarf spheroidal (dSph) galaxy, based on 34 individual spectra covering more than 2 yr of observations. This is the first time that orbital elements could be derived for a binary in a dSph. The system consists of a metal-poor red giant and a low-mass companion, possibly a white dwarf, with a 135 day period in a moderately eccentric (e = 0.18) orbit. Its period and eccentricity are fully consistent with metal-poor binaries in the Galactic halo, while the projected semimajor axis is small, at ap sin i = 38 R☉. In fact, a very close orbit could inhibit the production of heavier elements through s-process nucleosynthesis, leading to the very low abundances of neutron-capture elements that are found in this star. We discuss the further implications for the chemical enrichment history of the Hercules dSph, but find no compelling binary scenario that could reasonably explain the full, peculiar abundance pattern of the Hercules dSph galaxy.