Swift J1357.2-0933: the faintest black hole?
Swift J1357.2-0933: the faintest black hole?
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DOI：
10.1093/mnras/stu1487
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发表时间：
2014-04
影响因子：
4.8
通讯作者：
M. A. Padilla;M. A. Padilla;R. Wijnands;N. Degenaar;T. Muñoz-Darias;J. Casares;J. Casares;R. Fender
中科院分区：
文献类型：
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作者：
M. A. Padilla;M. A. Padilla;R. Wijnands;N. Degenaar;T. Muñoz-Darias;J. Casares;J. Casares;R. Fender
Swift J1357.2−0933 是一个已确认的非常微弱的黑洞 X 射线瞬变，估计轨道周期较短，为 2.8 小时。 2013 年 7 月，我们使用 XMM-Newton 观测了 Swift J1357.2−0933 约 50 ks 的静止状态。在 ∼3 × 10−15 erg cm−2 s−1 的 0.5-10 keV 未吸收通量下可以清楚地检测到源。如果源位于 1.5 kpc 的距离（如文献中建议的），这意味着光度为 ∼8 × 1029 erg s−1，使其成为检测到的最微弱的静态黑洞低质量 X 射线双星。这也意味着，在低至 2.8 小时的静止 X 射线光度与轨道周期图中没有任何反转的迹象，正如理论上和最近在 0.5-10 keV X 射线光度约为 1.2 × 1031 erg s−1 的 2.4 小时轨道周期黑洞 MAXI J1659−152 的检测所支持的那样。然而，Swift J1357.2−0933 的距离存在相当大的不确定性，可能最远为 6.3 kpc。在这种情况下，其静态光度将为 LX ∼ 1.3 × 1031 erg s−1，即类似于 MAXI J1659−152，因此，它支持这种分岔周期的存在。我们还用利物浦望远镜在 r′∼22.3 mag 处检测到了光学源，同时进行了 X 射线观测。 Swift J1357.2−0933 的 X 射线/光学光度比与黑洞在此静态 X 射线光度范围内的预期值一致。
Swift J1357.2−0933 is a confirmed very faint black hole X-ray transient and has a short estimated orbital period of 2.8 h. We observed Swift J1357.2−0933 for ∼50 ks with XMM-Newton in 2013 July during its quiescent state. The source is clearly detected at a 0.5-10 keV unabsorbed flux of ∼3 × 10−15 erg cm−2 s−1. If the source is located at a distance of 1.5 kpc (as suggested in the literature), this would imply a luminosity of ∼8 × 1029 erg s−1, making it the faintest detected quiescent black hole low-mass X-ray binary. This would also imply that there is no indication of a reversal in the quiescence X-ray luminosity versus orbital period diagram down to 2.8 h, as has been predicted theoretically and recently supported by the detection of the 2.4 h orbital period black hole MAXI J1659−152 at a 0.5-10 keV X-ray luminosity of ∼1.2 × 1031 erg s−1. However, there is considerable uncertainty in the distance of Swift J1357.2−0933 and it may be as distant as 6.3 kpc. In this case, its quiescent luminosity would be LX ∼ 1.3 × 1031 erg s−1, i.e. similar to MAXI J1659−152 and hence, it would support the existence of such a bifurcation period. We also detected the source in optical at r′ ∼ 22.3 mag with the Liverpool telescope, simultaneously to our X-ray observation. The X-ray/optical luminosity ratio of Swift J1357.2−0933 agrees with the expected value for a black hole at this range of quiescent X-ray luminosities.