Long-term optical and infrared variability of the BL Lac object PKS 0537 – 441
Long-term optical and infrared variability of the BL Lac object PKS 0537 – 441
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DOI：
10.1093/mnras/sts296
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发表时间：
2013-02
影响因子：
4.8
通讯作者：
Bing-Kai Zhang;Sen Wang;Xiao-Yun Zhao;B. Dai;Min Zha
中科院分区：
文献类型：
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作者：
Bing-Kai Zhang;Sen Wang;Xiao-Yun Zhao;B. Dai;Min Zha
研究了BL Lac天体PKS 0537−441的长期光学和红外变异性。该源在光学和红外波段表现出很强的变异性，并分析了光谱指数的长期变化。结果表明，光谱指数与亮度之间存在着复杂的关系。在低状态下，色度越亮，色度越红，即光谱随着亮度的增加而变陡，而在高状态下，光源呈现相反的趋势。利用离散相关函数法研究了不同波段间的相关性。结果表明，各光学波段和红外波段的变化具有很强的相关性，但没有明显的滞后性。然而，预计两个波段之间将有几分钟到几小时的时间滞后。因此，任何检测时间延迟的尝试都需要对源进行更密集的监视。结构函数分析表明，该源在34-46 d的短期时间尺度上发生变化，在光学V波段检测到24.5 min的日内变化。光发射直径估计为4.33 × 10 14 cm，中心黑洞的质量估计为2.3 × 10 8 M。
The long-term optical and infrared variability of the BL Lac object PKS 0537 − 441 has been studied. The source exhibits strong variability in the optical and infrared bands, and long-term variations of spectral indices have been analysed. The results indicate that there is a complex relationship between the spectral index and the brightness. In the low state, a redder-whenbrighter chromatism has been found, in the sense that the spectrum steepens as the brightness increases, whereas in the high state, the source shows an opposite trend. The correlations between different bands have been investigated by means of the discrete correlation function method. The results show that the variations in the various optical and infrared bands are strongly correlated, but with no significant lags. It is, however, expected that there will be time lags of minutes to hours between the bands. Therefore, any attempt to detect the time lag needs a much denser monitoring of the source. Structure function analysis suggests that the source varies with a short-term time-scale of 34–46 d. An intra-day variability with a 24.5-min time-scale has been detected in the optical V band. The optical emission diameter is estimated to be 4.33 × 10 14 cm, and the mass of the central black hole is estimated to be 2.3 × 10 8 M� .