X-Ray Point Sources in the Central Region of M31 as Seen by Chandra
X-Ray Point Sources in the Central Region of M31 as Seen by Chandra
复制标题
钱德拉观察到的 M31 中心区域的 X 射线点源
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
J. McClintock
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文献类型：
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作者：
A. Kong;Michael R. Garcia;F. Primini;S. Murray;R. Di Stefano;J. McClintock
我们报告钱德拉观测的中心区域的M31。通过结合1999年至2001年期间Chandra ACIS-I的8次观测，我们在M31的中心~17′ × 17′区域内确定了204个X射线源，探测极限为~2 × 1035 ergs-1。在这204个来源中，22个是球状星团，2个是超新星遗迹，9个是行星状星云，9个是超软源。通过比较单个图像，大约50%的来源在几个月的时间尺度上是可变的。我们还发现了13个瞬变，光变曲线显示出各种形状。我们还提取了20个最亮光源的能谱，它们可以很好地拟合一个单一的幂律，平均光子指数为1.8。12个源的光谱形状是可变的，这表明它们经历了状态变化。所有点源的光度函数都与先前的观测结果一致（在1.7 × 1037 ergs-1处光度突变的幂律定律被打破）。然而，当不同区域的X射线源被单独考虑时，得到不同的光度函数。这表明不同区域的星星形成历史可能不同。
We report on Chandra observations of the central region of M31. By combining eight Chandra ACIS-I observations taken between 1999 and 2001, we have identified 204 X-ray sources within the central ~17′ × 17′ region of M31, with a detection limit of ~2 × 1035 ergs s-1. Of these 204 sources, 22 are identified with globular clusters, two with supernova remnants, nine with planetary nebula, and nine with supersoft sources. By comparing individual images, about 50% of the sources are variable on timescales of months. We also found 13 transients, with light curves showing a variety of shapes. We also extracted the energy spectra of the 20 brightest sources; they can be well fitted by a single power law with a mean photon index of 1.8. The spectral shapes of 12 sources are shown to be variable, suggesting that they went through state changes. The luminosity function of all the point sources is consistent with previous observations (a broken power law with a luminosity break at 1.7 × 1037 ergs s-1). However, when the X-ray sources in different regions are considered separately, different luminosity functions are obtained. This indicates that the star formation history might be different in different regions.