LBT在Holmberg矮星系中发现一颗黄超巨星双星IX
LBT Discovery of a Yellow Supergiant Eclipsing Binary in the Dwarf Galaxy Holmberg IX
摘要：
在用大双筒望远镜对M81进行的光变巡天中，我们在矮星系Holmberg IX的视场中发现了一个特殊的食双星（MV ~ -7.1）。它的周期为272天，光变曲线与两颗恒星都溢出洛希叶的过度接触模型非常吻合。它由两颗黄超巨星（V-I ~ 1等，T_eff = 4800 K）组成，而不是更常见的红或蓝超巨星。这样的系统应该是罕见的。虽然我们没有在文献中找到任何类似的系统，但我们注意到了第二个例子。SMC F0超巨星R47是一颗明亮的（MV ~ -7.5）周期变星，其全天空自动巡天（ASAS）光变曲线与周期为181天的接触双星非常吻合。我们认为这些系统是超新星的祖先，如SN 2004 et和SN 2006 ov，它们似乎有黄色的祖先。双星的相互作用（质量转移，质量损失）限制了超巨星的大小，使其表面温度高于处于相同核心演化阶段的孤立恒星。我们还讨论了这个变量是一个长周期造父变星的可能性。
英文摘要：
In a variability survey of M81 using the Large Binocular Telescope we have discovered a peculiar eclipsing binary (MV ~ -7.1) in the field of the dwarf galaxy Holmberg IX. It has a period of 272 days and the light curve is well-fit by an overcontact model in which both stars are overflowing their Roche lobes. It is composed by two yellow supergiants (V-I ~ 1 mag, T_eff = 4800 K), rather than the far more common red or blue supergiants. Such systems must be rare. While we failed to find any similar systems in the literature, we did, however note a second example. The SMC F0 supergiant R47 is a bright (MV ~ -7.5) periodic variable whose All Sky Automated Survey (ASAS) light curve is well-fit as a contact binary with a 181 day period. We propose that these systems are the progenitors of supernovae like SN 2004et and SN 2006ov, which appeared to have yellow progenitors. The binary interactions (mass transfer, mass loss) limit the size of the supergiant to give it a higher surface temperature than an isolated star at the same core evolutionary stage. We also discuss the possibility of this variable being a long-period Cepheid.
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