Intraday Optical Multiband Observation of BL Lacertae
Intraday Optical Multiband Observation of BL Lacertae
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DOI：
10.3847/1538-4357/ac4490
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
Y. Fang;Yan Zhang;Qihang Chen;Jianghua Wu
中科院分区：
文献类型：
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作者：
Y. Fang;Yan Zhang;Qihang Chen;Jianghua Wu
从2019年9月18日至12月6日，我们用85厘米望远镜对B、V、R和I波段的BLLac进行了9个晚上的观测，共收集了2300多个数据点。使用最可靠的功率增强F检验和方差分析检验了所有日间光照曲线的变异性，并在五个晚上发现了日内变异性。由于我们的高精度和高时间分辨率的数据，在以下分析中取得了两个关键发现。(1)除了在大多数夜晚强烈的变蓝变亮之外，我们还观察到了在BLLac天体中很少发现的颜色反转。这表明，今夜注入的电子有两种不同的能量分布。(2)物体在一夜之间在颜色-星等图上出现顺时针方向的环路。这是在这个天体的光学波段中报道的第一个日内光谱滞后环，这表明波段间时间滞后。我们使用ZDCF、ICCF和标枪估计了频段间的滞后，发现V和R频段的变化分别落后于B频段约16分钟和18分钟。如果加速时间刻度比冷却时间刻度短得多，这种光学时间滞后是可以预料的。
We observed BL Lac in the B, V, R, and I bands with an 85 cm telescope on nine nights from 2019 September 18 to 2019 December 6. More than 2300 data points were collected. All intraday light curves were examined for variations by using the most reliable power-enhanced F-test and the ANOVA test, and intraday variability was found on five nights. Thanks to our high precision and high temporal resolution data, two key discoveries were made in the following analyses. (1) In addition to the strong bluer-when-brighter behavior on most nights, we observed a color reversal that is rarely found in BL Lac objects. This indicates that there are two different energy distributions of injected electrons on this night. (2) The object traced clockwise loops on the color–magnitude diagrams on one night. These are the first intraday spectral hysteresis loops reported in the optical bands in this object, suggesting interband time lags. We estimated the interband lags by using the ZDCF, ICCF, and JAVELIN, and found the variations in the V and R band lagged that in the B band by about 16 and 18 minutes, respectively. Such optical time lags are expected if the acceleration timescale is much shorter than the cooling timescale.