Interferometric Monitoring of Gamma-ray Bright AGNs: OJ 287

Abstract

We present the results of simultaneous multi-frequency imaging observations at 22, 43, 86, and 129\,GHz of OJ\,287. We used the Korean VLBI Network as part of the Interferometric MOnitoring of GAmma-ray Bright active galactic nuclei (iMOGABA). The iMOGABA observations were performed during 31 epochs from 2013 January 16 to 2016 December 28. We also used 15\,GHz OVRO and 225\,GHz SMA flux density data. We analyzed four flux enhancements in the light curves. The estimated time scales of three flux enhancements were similar with time scales of $\sim$50 days at two frequencies. A fourth flux enhancement had a variability timescale approximately twice as long. We found that 225\,GHz enhancements led the 15\,GHz enhancements by a range of 7 to 30 days in the time delay analysis. We found the fractional variability did not change with frequency between 43 and 86\,GHz. We could reliably measure the turnover frequency, ${\nu }_{\mathrm{c}}$, of the core of the source in three epochs. This was measured to be in a range from 27 to 50\,GHz and a flux density at the turnover frequency, $S_{\mathrm{m}}$, ranging from 3-6\,Jy. The derived SSA magnetic fields, $B_{\mathrm{SSA}}$, are in a range from $0.157\pm 0.104$ to $0.255\pm 0.146$ mG. We estimated the equipartition magnetic field strengths to be in a range from $0.95\pm 0.15$ to $1.93\pm 0.30$ mG. The equipartition magnetic field strengths are up to a factor of 10 higher than the values of $B_{\mathrm{SSA}}$. We conclude that the downstream jet may be more particle energy dominated.

27 pages, 9 figures, Accepted for publication in ApJ

References in corpus (12)

• A massive binary black-hole system in OJ287 and a test of general relativity
• Kinematics of Parsec-Scale Jets of Gamma-Ray Blazars at 43~GHz within the VLBA-BU-BLAZAR Program
• DiFX: A software correlator for very long baseline interferometry using multi-processor computing environments
• Location of Gamma-ray emission and magnetic field strengths in OJ 287
• Interferometric Monitoring of Gamma-ray Bright AGNs I: Results of Single-epoch Multifrequency Observations
• Resolving the Geometry of the Innermost Relativistic Jets in Active Galactic Nuclei
• Ejection of Double knots from the radio core of PKS 1510--089 during the strong gamma-ray flares in 2015
• Exploring the Variability of the Flat Spectrum Radio Source 1633+382. I. Phenomenology of the Light Curves
• Discovery of a wandering radio jet base after a large X-ray flare in the blazar Markarian 421
• Interferometric Monitoring of Gamma-ray Bright AGNs: S5 0716+714
• OVRO 40m blazar monitoring program: Understanding the relationship between 15 GHz radio variability properties and gamma-ray activity in blazars
• Simultaneous dual-frequency radio observations of S5 0716+714: A search for intraday variability with the Korean VLBI Network

Cited by in corpus (8)

• X-ray spectral components of the blazar and binary black hole candidate OJ 287 (2005-2020)
• MOMO VI: Multifrequency radio variability of the blazar OJ 287 from 2015-2022, absence of predicted 2021 precursor-flare activity, and a new binary interpretation of the 2016/2017 outburst
• MOMO IV: The complete Swift X-ray and UV/optical light curve and characteristic variability of the blazar OJ 287 during the last two decades
• Magnetic Field Strengths of the Synchrotron Self-Absorption Region in the Jet of CTA 102 During Radio Flares
• MOMO V. Effelsberg, Swift and Fermi study of the blazar and supermassive binary black hole candidate OJ 287 in a period of high activity
• Interferometric Monitoring of Gamma-ray Bright AGNs: Measuring the Magnetic Field Strength of 4C +29.45
• Unveiling the Bent Jet Structure and Polarization of OJ 287 at 1.7 GHz with Space VLBI
• Double SSA Spectrum and Magnetic Field Strength of the FSRQ 3C 454.3