Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst
- Indian Institute of Astrophysics, Block II, Koramangala, Bangalore-560034 (India)
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 χ {sup 2}-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 δ {sub 0}=1.17, the magnetic field strength B≤3.8 G, and the size of the emitting region R{sub s}<2.28× 10{sup 14} 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.
- OSTI ID:
- 22663912
- Journal Information:
- Astrophysical Journal, Vol. 835, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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