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arXiv 0808.2282astro-ph
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斯隆数字巡天中的候选盘宽双星

Candidate Disk Wide Binaries in the Sloan Digital Sky Survey

Branimir Sesar, Zeljko Ivezic, Mario Juric

备注：
emulateApJ, 47 pages, 28 figures, accepted to ApJ
发表信息：
Astrophys.J.689:1244-1273,2008
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摘要：

使用SDSS数据Release 6，我们构造了两个独立的候选恒星宽双星样本，它们被选为i）角距在3“-16”范围内的未分辨源对，ii）角距在5“-30”范围内的共同自行对，并使它们公开可用。这些样本以盘星为主，我们用它们来约束主序星测光视差关系M_r（r-i）的形状，并研究宽双星系统的性质。我们通过寻找一个关系来估计M_r（r-i），该关系使宽二进制候选的主分量和次分量的距离模之间的差最小化。我们用四次多项式对M_r（r-i）进行建模，并对每个样本独立地使用马尔可夫链蒙特卡罗拟合来确定系数。利用导出的光度视差关系，我们构造了一系列高质量的主序星候选双星表。利用这些星表，我们研究了宽双星a在2，000 < a <47，000 AU范围内的半长轴分布。我们发现观测值可以很好地用Opik分布f（a）~1/a来描述，其中a< a_{break}，其中a_{break}随银道面以上的高度Z近似线性地增加（a_{break} ~ 12，300 Z[kpc]^0.7 AU）。100 AU < a < a_{break}的宽双星系统的数量，作为恒星总数的一部分，从Z=0.5 kpc时的0.9%减少到Z=3 kpc时的0.5%。一颗恒星在宽双星系统中的概率与它的颜色无关。在这种颜色下，红色分量的伴星似乎是从恒星光度函数中随机抽取的，而蓝色分量的蓝红伴星比比从光度函数中预期的要大。

英文摘要：

Using SDSS Data Release 6, we construct two independent samples of candidate stellar wide binaries selected as i) pairs of unresolved sources with angular separation in the range 3'' - 16'', ii) common proper motion pairs with 5'' - 30'' angular separation, and make them publicly available. These samples are dominated by disk stars, and we use them to constrain the shape of the main-sequence photometric parallax relation M_r(r-i) and to study the properties of wide binary systems. We estimate M_r(r-i) by searching for a relation that minimizes the difference between distance moduli of primary and secondary components of wide binary candidates. We model M_r(r-i) by a fourth degree polynomial and determine the coefficients using Markov Chain Monte Carlo fitting, independently for each sample. Aided by the derived photometric parallax relation, we construct a series of high-quality catalogs of candidate main-sequence binary stars. Using these catalogs, we study the distribution of semi-major axes of wide binaries, a, in the 2,000 < a < 47,000 AU range. We find the observations to be well described by the Opik distribution, f(a)~1/a, for a<a_{break}, where a_{break} increases roughly linearly with the height Z above the Galactic plane (a_{break}~12,300 Z[kpc]^0.7 AU). The number of wide binary systems with 100 AU < a < a_{break}, as a fraction of the total number of stars, decreases from 0.9% at Z=0.5 kpc to 0.5% at Z=3 kpc. The probability for a star to be in a wide binary system is independent of its color. Given this color, the companions of red components seem to be drawn randomly from the stellar luminosity function, while blue components have a larger blue-to-red companion ratio than expected from luminosity function.

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