Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst
Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst
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DOI：
10.3847/1538-4357/835/2/275
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发表时间：
2016-12
期刊：
影响因子：
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通讯作者：
S. Rakshit;C. .. Stalin;S. Muneer;S. Neha;V. Paliya
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文献类型：
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作者：
S. Rakshit;C. .. Stalin;S. Muneer;S. Neha;V. Paliya
伽马射线耀变体OJ 287在2015年12月至2016年2月期间处于高活动状态。与这种高亮度状态相一致，我们在r波段观测了40个夜晚的光度测定，在uvb - RI波段观测了9个时期的偏振测定。观测期间，光源亮度变化范围为13.20±0.04等~ 14.98±0.04等，r波段偏振度(P)波动范围为6.0%±0.3% ~ 28.3%±0.8%。专注于夜间光学变异性（INOV），我们使用χ2统计发现占空比约为71%，类似于已知的blazars。从INOV数据估计，最短变率时间尺度为142±38分钟，得到观测到的多普勒因子δ0 = 1.17的下限，磁场强度B≤3.8 G，发射区尺寸Rs < 2.28 × 1014 cm。在夜间时间尺度上，r波段通量与P之间存在显著的反相关关系。在u波段观测到的P值通常大于在较长波长波段观测到的P值，表明存在波长依赖偏振。利用我们在监测期间获得的Steward天文台的v波段光度和偏振数据，我们发现P波段和v波段亮度之间存在不同的相关性。虽然有时在P波段和v波段之间看到反相关，但在其他时候没有看到相关，从而表明在OJ 287的喷流中存在不止一个短暂的激波成分。
The gamma-ray blazar OJ 287 was in a high activity state during 2015 December–2016 February. Coinciding with this high brightness state, we observed this source for photometry on 40 nights in R-band and for polarimetry on nine epochs in UBV RI bands. During the period of our observations, the source brightness varied from 13.20 ± 0.04 mag to 14.98 ± 0.04 mag and the degree of polarization (P) fluctuated between 6.0% ± 0.3% and 28.3% ± 0.8% in R-band. Focusing on intranight optical variability (INOV), we find a duty cycle of about 71% using χ2-statistics, similar to that known for blazars. From INOV data, the shortest variability timescale is estimated to be 142 ± 38 minutes, yielding a lower limit of the observed Doppler factor δ0 = 1.17, the magnetic field strength B ≤ 3.8 G, and the size of the emitting region Rs < 2.28 × 1014 cm. On internight timescales, a significant anticorrelation between R-band flux and P is found. The observed P at U-band is generally larger than that observed at longer-wavelength bands, suggesting a wavelength-dependent polarization. Using V-band photometric and polarimetric data from Steward Observatory obtained during our monitoring period, we find a varied correlation between P and V-band brightness. While an anticorrelation is sometimes seen between P and V-band magnitude, no correlation is seen at other times, thereby suggesting the presence of more than one short-lived shock component in the jet of OJ 287.