人马座A的600分钟近红外光曲线 *
A 600 minute near-infrared lightcurve of Sagittarius A*
摘要：
我们目前最长的，由一个因素的两倍，近红外光曲线从银河系中心的超大质量黑洞的Sgr A*。通过结合Keck和VLT数据从一个共同的夜晚，其中偶然有同时钱德拉和SMA数据，这个光变曲线是用来解决两个突出的问题。首先，一个假定的准周期约为20分钟的小组报告使用ESO的VLT是不确定的凯克观测。第二，虽然红外和毫米-制度被认为是相关的基础上，从两个波长域的光变曲线之间的时间滞后，20分钟的报告时间滞后推断使用这个共同的VLT/凯克夜晚的凯克数据仅是在不一致的滞后约100分钟的早期报告。通过我们的长光变曲线，我们发现：（i）1.3毫米的同时观测实际上与~100分钟的时间滞后是一致的，（ii）VLT和Keck小组使用的不同的近红外测光方法导致一致的结果，（iii）整个近红外光变曲线的Lomb-Scargle周期图是无特征的，并且遵循斜率为-1.6的幂律，以及（iv）用滑动窗口扫描光变曲线以寻找瞬态QPO现象，对于光变曲线的某个部分，在周期图中显示25分钟的峰值。使用蒙特卡罗模拟并考虑试验次数，我们发现它是微不足道的。
英文摘要：
We present the longest, by a factor of two, near-infrared lightcurve from Sgr A* - the supermassive black hole in the Galactic center. Achieved by combining Keck and VLT data from one common night, which fortuitously had simultaneous Chandra and SMA data, this lightcurve is used to address two outstanding problems. First, a putative quasi-periodicity of ~20 min reported by groups using ESO's VLT is not confirmed by Keck observations. Second, while the infrared and mm-regimes are thought to be related based on reported time lags between lightcurves from the two wavelength domains, the reported time lag of 20 min inferred using the Keck data of this common VLT/Keck night only is at odds with the lag of ~100 min reported earlier. With our long lightcurve, we find that (i) the simultaneous 1.3 millimeter observations are in fact consistent with a ~100 min time lag, (ii) the different methods of NIR photometry used by the VLT and Keck groups lead to consistent results, (iii) the Lomb-Scargle periodogram of the whole NIR lightcurve is featureless and follows a power-law with slope -1.6, and (iv) scanning the lightcurve with a sliding window to look for a transient QPO phenomenon reveals for a certain part of the lightcurve a 25 min peak in the periodogram. Using Monte Carlo simulations and taking the number of trials into account, we find it to be insignificant.
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