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arXiv 1306.5843astro-ph.SR
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疏散星团NGC 7142分叉处分离双星的分析

Analysis of Detached Eclipsing Binaries near the Turnoff of the Open Cluster NGC 7142

Eric L. Sandquist, Matthew Shetrone, Andrew W. Serio, Jerome Orosz

摘要:

本文分析了老疏散星团NGC 7142中三颗双线深食双星的BVRI测光和视向速度测量结果。短周期(P = 1.9096825 d)的分离双星V375 Cep是一个高概率的星团成员,它有一次伴星的全食。主恒星(M=1.288+/-0.017太阳)在星团转折处的特征显示其年龄为3.6 Gyr(随机不确定度为0.25 Gyr),与先前对色星等图的分析一致。第二颗恒星(M = 0.871+/-0.008 Msun)预计不会有显著的演化,但其半径比模型预测的大10%以上。因为这个双星系统有一个已知的年龄,它是有用的测试的想法,半径膨胀可以发生在短周期的双星与显着的对流信封由于能量传输的抑制磁场。联星中较亮的恒星也产生了距离模数的精确估计,与红化估计无关:(m-M)_V=12.86+/-0.07。另外两个食双星系统不是星团成员,尽管其中一个系统(V2)只有在恒星特征被确定后才能最终排除是现在或以前的成员。这颗双星的边缘在0.5度以内,是一颗相当长周期的偏心双星,包含两颗几乎无法分辨的恒星。另一颗双星(V1)虽然轨道周期小于5 d,但离心率却很小(e=0.038)。

英文摘要:

We analyze extensive BVRI photometry and radial velocity measurements for three double-lined deeply-eclipsing binary stars in the field of the old open cluster NGC 7142. The short period (P = 1.9096825 d) detached binary V375 Cep is a high probability cluster member, and has a total eclipse of the secondary star. The characteristics of the primary star (M=1.288+/-0.017 Sun) at the cluster turnoff indicate an age of 3.6 Gyr (with a random uncertainty of 0.25 Gyr), consistent with earlier analysis of the color-magnitude diagram. The secondary star (M = 0.871+/-0.008 Msun) is not expected to have evolved significantly, but its radius is more than 10% larger than predicted by models. Because this binary system has a known age, it is useful for testing the idea that radius inflation can occur in short period binaries for stars with significant convective envelopes due to the inhibition of energy transport by magnetic fields. The brighter star in the binary also produces a precision estimate of the distance modulus, independent of reddening estimates: (m-M)_V=12.86+/-0.07. The other two eclipsing binary systems are not cluster members, although one of the systems (V2) could only be conclusively ruled out as a present or former member once the stellar characteristics were determined. That binary is within 0.5 degrees of edge-on, is in a fairly long-period eccentric binary, and contains two almost indistiguishable stars. The other binary (V1) has a small but nonzero eccentricity (e=0.038) in spite of having an orbital period under 5 d.

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