arXiv 0704.06552007-04-04astro-ph

利用斯隆数字巡天探索变化的天空

Exploring the Variable Sky with the Sloan Digital Sky Survey

Branimir Sesar, Zeljko Ivezic, Robert H. Lupton, Mario Juric, James E. Gunn, Gillian R. Knapp, Nathan De Lee, J. Allyn Smith, Gajus Miknaitis, Huan Lin, Douglas… 展开作者

Branimir Sesar, Zeljko Ivezic, Robert H. Lupton, Mario Juric, James E. Gunn, Gillian R. Knapp, Nathan De Lee, J. Allyn Smith, Gajus Miknaitis, Huan Lin, Douglas Tucker, Mamoru Doi, Masayuki Tanaka, Masataka Fukugita, Jon Holtzman, Steve Kent, Brian Yanny, David Schlegel, Douglas Finkbeiner, Nikhil Padmanabhan, Constance M. Rockosi, Nicholas Bond, Brian Lee, Chris Stoughton, Sebastian Jester, Hugh Harris, Paul Harding, Jon Brinkmann, Donald P. Schneider, Donald York, Michael W. Richmond, Daniel Vanden Berk

备注：: 41 pages, 14 figures, submitted to Astronomical Journal
发表信息：: Astron.J.134:2236-2251,2007
DOI：: 10.1086/521819

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摘要：

我们使用基于多个SDSS成像观测的目录来量化微弱的未分辨光源的可变性。该星表涵盖SDSS Stripe 82，并包含SDSS ugriz系统中140万个未解析源的5800万个光度观测。在每个光度带通中，我们计算各种低阶光变曲线统计，并使用它们来选择和研究变量源。我们发现，2%的未解决的光源亮度比g=20.5出现在0.05 mag级（rms）同时在g和r波段的变量。这些可变源中的大多数（2/3）是低红移（<2）类星体，尽管它们只占所采用的通量限制样本中所有源的2%。我们发现，至少有90%的类星体是可变的0.03等的水平（rms），并确认可变性是一个很好的方法来寻找低红移类星体是紫外线过剩的颜色选择（在银河系高纬度）。我们分析了类星体的光变曲线偏度的分布，发现其中心为零。我们发现大约1/4的变星是天琴座RR型变星，并且只有0.5%的恒星在0.05等的水平上是变星。在主恒星轨迹上的g-r与u-g色图中，光变曲线偏度的分布被发现是双峰的（其中一个模式与Algol行为一致）。使用超过600 RR天琴座恒星，我们展示了丰富的晕子结构的距离为100千秒差距。我们将这些结果外推到大型综合巡天望远镜的预期性能，并估计它将获得约200万个低红移类星体的良好采样的2%精度，多色光变曲线，并将发现至少5000万颗变星。

英文摘要：

We quantify the variability of faint unresolved optical sources using a catalog based on multiple SDSS imaging observations. The catalog covers SDSS Stripe 82, and contains 58 million photometric observations in the SDSS ugriz system for 1.4 million unresolved sources. In each photometric bandpass we compute various low-order lightcurve statistics and use them to select and study variable sources. We find that 2% of unresolved optical sources brighter than g=20.5 appear variable at the 0.05 mag level (rms) simultaneously in the g and r bands. The majority (2/3) of these variable sources are low-redshift (<2) quasars, although they represent only 2% of all sources in the adopted flux-limited sample. We find that at least 90% of quasars are variable at the 0.03 mag level (rms) and confirm that variability is as good a method for finding low-redshift quasars as is the UV excess color selection (at high Galactic latitudes). We analyze the distribution of lightcurve skewness for quasars and find that is centered on zero. We find that about 1/4 of the variable stars are RR Lyrae stars, and that only 0.5% of stars from the main stellar locus are variable at the 0.05 mag level. The distribution of lightcurve skewness in the g-r vs. u-g color-color diagram on the main stellar locus is found to be bimodal (with one mode consistent with Algol-like behavior). Using over six hundred RR Lyrae stars, we demonstrate rich halo substructure out to distances of 100 kpc. We extrapolate these results to expected performance by the Large Synoptic Survey Telescope and estimate that it will obtain well-sampled 2% accurate, multi-color lightcurves for ~2 million low-redshift quasars, and will discover at least 50 million variable stars.

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