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Title: Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst

Abstract

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 -bandmore » 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.« less

Authors:
; ; ;  [1];  [2]
  1. Indian Institute of Astrophysics, Block II, Koramangala, Bangalore-560034 (India)
  2. Aryabhatta Research Institute of Observational Sciences (ARIES), 263002, Nainital (India)
Publication Date:
OSTI Identifier:
22663912
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BL LACERTAE OBJECTS; BRIGHTNESS; CORRELATIONS; COSMIC GAMMA SOURCES; DOPPLER EFFECT; GALAXIES; GAMMA RADIATION; MAGNETIC FIELDS; PHOTOMETRY; POLARIMETRY; POLARIZATION; STATISTICS; WAVELENGTHS

Citation Formats

Rakshit, Suvendu, Stalin, C. S., Muneer, S., Paliya, Vaidehi S., and Neha, S., E-mail: suvenduat@gmail.com. Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/2/275.
Rakshit, Suvendu, Stalin, C. S., Muneer, S., Paliya, Vaidehi S., & Neha, S., E-mail: suvenduat@gmail.com. Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst. United States. doi:10.3847/1538-4357/835/2/275.
Rakshit, Suvendu, Stalin, C. S., Muneer, S., Paliya, Vaidehi S., and Neha, S., E-mail: suvenduat@gmail.com. Wed . "Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst". United States. doi:10.3847/1538-4357/835/2/275.
@article{osti_22663912,
title = {Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst},
author = {Rakshit, Suvendu and Stalin, C. S. and Muneer, S. and Paliya, Vaidehi S. and Neha, S., E-mail: suvenduat@gmail.com},
abstractNote = {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.},
doi = {10.3847/1538-4357/835/2/275},
journal = {Astrophysical Journal},
number = 2,
volume = 835,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}
  • Suzaku observations of the blazar OJ 287 were performed in 2007 April 10-13 and November 7-9. They correspond to a quiescent and a flaring state, respectively. The X-ray spectra of the source can be well described with single power-law models in both exposures. The derived X-ray photon index and the flux density at 1 keV were found to be {Lambda} = 1.65 {+-} 0.02 and S{sub 1keV} = 215 {+-} 5 nJy, in the quiescent state. In the flaring state, the source exhibited a harder X-ray spectrum ({Lambda} = 1.50 {+-} 0.01) with a nearly doubled X-ray flux density S{submore » 1keV} = 404{sub -5}{sup +6} nJy. Moreover, significant hard X-ray signals were detected up to {approx} 27 keV. In cooperation with the Suzaku, simultaneous radio, optical, and very-high-energy {gamma}-ray observations of OJ 287 were performed with the Nobeyama Millimeter Array, the KANATA telescope, and the MAGIC telescope, respectively. The radio and optical fluxes in the flaring state (3.04 {+-} 0.46 Jy and 8.93 {+-} 0.05 mJy at 86.75 Hz and in the V-band, respectively) were found to be higher by a factor of 2-3 than those in the quiescent state (1.73 {+-} 0.26 Jy and 3.03 {+-} 0.01 mJy at 86.75 Hz and in the V-band, respectively). No notable {gamma}-ray events were detected in either observation. The spectral energy distribution of OJ 287 indicated that the X-ray spectrum was dominated by inverse Compton radiation in both observations, while synchrotron radiation exhibited a spectral cutoff around the optical frequency. Furthermore, no significant difference in the synchrotron cutoff frequency was found between the quiescent and flaring states. According to a simple synchrotron self-Compton model, the change of the spectral energy distribution is due to an increase in the energy density of electrons with small changes of both the magnetic field strength and the maximum Lorentz factor of electrons.« less
  • This paper studies the color behavior of the BL Lac object OJ 287 during an optical outburst. Upon revisiting the data from the OJ 94 monitoring project, and from an analysis of the data obtained with the 60/90 cm Schmidt Telescope of NAOC, we found a bluer-when-brighter chromatism in this object. The amplitude of variation tends to decrease with frequency. These results are consistent with the shock-in-jet model. We ran some simulations and confirmed that both amplitude difference and time delay between variations at different wavelengths can result in the bluer-when-brighter phenomenon. Our observations confirmed that OJ 287 underwent amore » double-peaked outburst about 12 years after 1996, which provides further evidence for the binary black hole model in this object.« less