Two Power-Law States of the Ultraluminous X-Ray Source IC 342 X-1
Two Power-Law States of the Ultraluminous X-Ray Source IC 342 X-1
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DOI：
10.1093/pasj/65.2.48
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发表时间：
2012-12
影响因子：
2.3
通讯作者：
Tessei Yoshida;N. Isobe;S. Mineshige;A. Kubota;T. Mizuno;Kei Saitou
中科院分区：
文献类型：
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作者：
Tessei Yoshida;N. Isobe;S. Mineshige;A. Kubota;T. Mizuno;Kei Saitou
为了阐明超亮X射线源（ULX）在其幂律（PL）状态下的发射特性，我们使用我们自己的朱雀数据和XMM-Newton、Chandra和Swift观测的存档数据，检查了IC 342 X-1在PL状态下的长期X射线光谱数据。根据0.5-10 keV波段的X射线亮度，该源的PL态可分为两个亚态：低亮度PL态（4-6）× 10 39 erg s·1）和高亮度PL态（1.1-1.4）× 10 40 erg s·1）。在2010年8月和2011年3月的朱雀观测中，X-1保持在低光度的PL状态。观测到的X射线光度（4.9-5.6 × 10 39 erg s·1）和光谱形状（光子指数= 1.67-1.83）在两次观测之间略有变化。使用朱雀PIN探测器，我们第一次证实了PL尾巴延伸到至少20千电子伏，没有签名的高能量周转在两个朱雀观测。与此相反，在2004年和2005年的高亮度PL状态与XMM-牛顿在约6千电子伏的营业额进行了观察。重要的是，两个PL态之间的光子指数是相似的，y β 1的康普顿y参数也是相似的，这表明尽管电子温度不同，但两个PL态中保持着相似的能量平衡（在日冕和吸积盘之间）。从最近关于其他ULX的研究和银河系黑洞双星GRS 1915+105的光谱相似性来看，IC 342 X-1也可能处于超临界吸积速率的状态，尽管需要更灵敏的更高能量观测才能得出任何结论。
In order to elucidate the emission properties of ultraluminous X-ray sources (ULXs) during their power-law (PL) state, we examined long-term X-ray spectral data of IC 342 X-1 during its PL state by using our own Suzaku data and archival data by XMM-Newton, Chandra, and Swift observations. The PL state of this source seems to be classified into two sub-states in terms of the X-ray luminosities in the 0.5–10 keV band: the low-luminosity PL state with (4–6) � 10 39 erg s � 1 and the high-luminosity one with (1.1–1.4) � 10 40 erg s � 1 . During Suzaku observations, which were made in 2010 August and 2011 March, X-1 stayed in the low-luminosity PL state. The observed X-ray luminosity (4.9–5.6 � 10 39 erg s � 1 ) and the spectral shape (photon index = 1.67–1.83) slightly changed between the two observations. Using the Suzaku PIN detector, we for the first time confirmed a PL tail extending up to at least 20 keV with no signatures of a high-energy turnover in both of the Suzaku observations. In contrast, a turnover at about 6 keV was observed during the high-luminosity PL state in 2004 and 2005 with XMM-Newton. Importantly, the photon indices are similar between the two PL states, and so are the Compton y-parameters of y � 1, which indicates a similar energy balance (between the corona and the accretion disk) holding in the two PL states despite different electron temperatures. From spectral similarities with recent studies about other ULXs, and the Galactic black-hole binary GRS 1915+105, IC 342 X-1 is also likely to be in a state with a supercritical accretion rate, although more sensitive higher energy observations would be necessary to make any conclusion.