Title: Discovery and state transitions of the new Galactic black hole candidate MAXI J1535-571 Show Chinese title

Title: 新银河系黑洞候选体MAXI J1535-571的发现和状态转换

Abstract: We report on the detection and subsequent X-ray monitoring of the new Galactic black hole candidate MAXI J1535-571 with the MAXI/GSC. Afterthe discovery on 2017 September 2 made independently with MAXI and the Swift/BAT, the source brightened gradually, and in a few weeks, reached the peak intensity of ~5 Crab, or ~1.6 x 10^{-7} erg cm^{-2} s^{-1} in terms of the 2--20 keV flux. On the initial outburst rise, the X-ray spectrum was described by a power-law model with a photon index of ~2, while after a hard-to-soft transition which occurred on September 18, the spectrum required a disk blackbody component in addition. At around the flux peak, the 2-8 keV and 15-50 keV light curves showed quasi-periodic and anti-correlated fluctuations with an amplitude of 10--20%, on a time scale of ~1-day. Based on these X-ray properties obtained with the MAXI/GSC, we discuss the evolution of the spectral state of this source, and give constraints on its system parameters. Show Chinese abstract

Abstract: 我们报告了利用MAXI/GSC对新的银河系黑洞候选体MAXI J1535-571的探测及其后续X射线监测。在2017年9月2日分别通过MAXI和Swift/BAT独立发现该源后，其亮度逐渐增强，并在几周内达到约5 Crab的峰值强度，即在2–20 keV流量方面约为1.6 x 10^{-7} erg cm^{-2} s^{-1} 。在初始爆发上升阶段，X射线谱由一个光子指数约为2的幂律模型描述，而在9月18日发生从硬到软的转变后，谱需要额外的盘黑体成分。在通量峰值附近，2–8 keV和15–50 keV的光曲线显示出幅度为10–20%、时间尺度约为1天的准周期性反相关波动。基于MAXI/GSC获得的这些X射线特性，我们讨论了该源的光谱状态演化，并对其系统参数给出了限制。