J/ApJ/902/104 Korean VLBI Network monitoring of OJ 287 (Lee+, 2020)
Interferometric monitoring of gamma-ray bright AGNs: OJ 287.
Lee J.W., Lee S.-S., Algaba J.-C., Hodgson J., Kim J.-Y., Park J., Kino M.,
Kim D.-W., Kang S., Yoo S., Kim S.H., Gurwell M.
<Astrophys. J., 902, 104 (2020)>
=2020ApJ...902..104L 2020ApJ...902..104L
ADC_Keywords: Interferometry; BL Lac objects; Radio lines
Keywords: Very long baseline interferometry ; BL Lacertae objects ;
Active galactic nuclei ; Radio jets
Abstract:
We present the results of simultaneous multifrequency imaging
observations at 22, 43, 86, and 129GHz of OJ 287. We used the Korean
Very Long Baseline Interferometry 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 15GHz OVRO and
225GHz SMA flux density data. We analyzed four flux enhancements in
the light curves. The estimated timescales of three flux enhancements
were similar with timescales of ∼50d at two frequencies. A fourth flux
enhancement had a variability timescale approximately twice as long.
We found that 225GHz enhancements led the 15GHz enhancements by a
range of 7-30d in the time delay analysis. We found the fractional
variability did not change with frequency between 43 and 86GHz. We
could reliably measure the turnover frequency, νc, of the core of
the source in three epochs. This was measured to be in a range from
27 to 50GHz and a flux density at the turnover frequency, Sm,
ranging from 3 to 6Jy. The derived SSA magnetic fields, BSSA, are in
a range from 0.157±0.104 to 0.255±0.146mG. We estimated the
equipartition magnetic field strengths to be in a range from
0.95±0.15 to 1.93±0.30mG. The equipartition magnetic field
strengths are up to a factor of 10 higher than the values of BSSA.
We conclude that the downstream jet may be more particle energy
dominated.
Description:
OJ 287 was observed by the Korean VLBI Network (KVN), which is a 500km
scale VLBI network consisting of three 21m radio telescopes located in
Seoul (KVN Yonsei), Ulsan (KVN Ulsan), and Jeju (KVN Tamna), Korea.
The observations were conducted at 22, 43, 86, and 129GHz bands
simultaneously with a mean cadence of roughly a month since
2012 December except for maintenance seasons from June to August.
The angular resolution of the KVN is 6mas at 22GHz, 3mas at 43GHz,
1.5mas at 86GHz, and 1mas at 129GHz. We used data obtained in
31 epochs in the period from 2013 January 16 (MJD 56308) until
2016 December 28 (MJD 57750).
Objects:
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RA (ICRS) DE Designation(s)
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08 54 48.87 +20 06 30.6 OJ 287 = QSO J0854+2006
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 62 106 Image parameters
table2.dat 66 106 Modelfit parameters for the center of images
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See also:
J/A+AS/129/569 : BVRI photometry of OJ 287 (Jia Guibin+ 1998)
J/A+AS/132/83 : BVRI photometry of 7 BL Lac objects (Bai+ 1998)
J/A+AS/136/455 : BVRI photometry of 3 BL Lac objects (Bai+, 1999)
J/ApJ/522/846 : Optical monitoring of GeV loud blazars (Xie+, 1999)
J/A+AS/146/141 : Intensive monitoring of OJ 287 (Pursimo+, 2000)
J/AJ/130/1418 : AGN jet kinematics (Jorstad+, 2005)
J/AJ/132/1256 : eim BATC photometry of OJ 287 (Wu+, 2006)
J/A+A/450/39 : BVRI photometry of 8 red blazars (Gu+, 2006)
J/AJ/134/799 : Multiwaveband polarimetry of 15 AGN (Jorstad+, 2007)
J/MNRAS/385/823 : UBVRI light curves of OJ 287 (Zheng+, 2008)
J/MNRAS/402/2087 : Opt. polarization of OJ 287 in 2005-2009 (Villforth+, 2010)
J/AJ/141/65 : BATC ceimo light curves of OJ 287 (Dai+, 2011)
J/ApJ/747/63 : 7mm VLBA observations of BL Lac object OJ287 (Agudo+, 2012)
J/A+A/545/A113 : MOJAVE IX. Core shift effects (Pushkarev+, 2012)
J/MNRAS/421/1861 : OJ287 polarization and VLBI jet direction (Valtonen+, 2012)
J/ApJ/764/5 : BR phot. of 2012 precursor flare in OJ287 (Pihajoki+, 2013)
J/A+A/559/A20 : Historical outbursts of OJ287 (Hudec+, 2013)
J/A+A/597/A80 : GMVA 86GHz images of OJ 287 (Hodgson+, 2017)
J/ApJ/835/275 : OJ 287 flux & pol. during 2016 outburst (Rakshit+, 2017)
J/ApJ/846/98 : Jet kinematics of blazars at 43GHz with VLBA (Jorstad+, 2017)
J/A+A/601/A12 : S5 0716+714 VLBI K- and Q-band variability (Lee+, 2017)
J/ApJ/862/1 : Rotation reversals in OJ 287 polarization (Cohen+, 2018)
J/A+A/609/A68 : Full-Stokes polarimetry of 5 radio sources (Myserlis+, 2018)
J/A+A/610/A74 : OJ 287 far-infrared photometry (Kidger+, 2018)
J/A+A/619/A88 : OJ287 high cadence polarization monitoring (Myserlis+, 2018)
J/A+A/626/A60 : F-GAMMA 2.6-43GHz radio data over 2007-2015 (Angelakis+, 2019)
J/AJ/157/95 : Optical variability of OJ 287 in 2016-2017 (Gupta+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Obs.Y [2013/2016] Year of the observation epoch
6- 8 A3 "month" Obs.M Month of the observation epoch
10- 11 I2 d Obs.D Day of the observation epoch
13- 17 I5 d MJD [56308/57751] Modified Julian Date of observation
19 A1 --- Band Observing frequency band (G1)
21- 25 F5.3 mas Bmaj [0.86/9.8] Major axis of restoring beam
27- 31 F5.3 mas Bmin [0.4/3.72] Minor axis of restoring beam
33- 37 F5.1 deg BPA [-89.2/89.2] Position angle of restoring
beam major axis
39- 43 F5.3 Jy SKVN [1.36/8.5] Total cleaned KVN flux density
45- 49 F5.3 Jy/beam Sp [1.3/8.4] Peak flux density
51- 53 I3 Jy/beam sigma [8/363] Off-source RMS in image
55- 57 I3 --- D [7/470] Dynamic range of image
59- 62 F4.2 --- xi-r [0.4/0.9] Quality of residual noise in image (1)
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Note (1): (i.e., ratio of the image root-mean-square noise to its
mathematical expectation).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Obs.Y [2013/2016] Year of the observation epoch
6- 8 A3 "month" Obs.M Month of the observation epoch
10- 11 I2 d Obs.D Day of the observation epoch
13- 17 I5 d MJD [56308/57751] Modified Julian Date of
observation
19 A1 --- Band Observing frequency band (G1)
21- 24 F4.2 Jy Stot [1.3/8.4] Model flux density (2)
26- 29 F4.2 Jy e_Stot [0.02/2.3] Uncertainty in Stot
31- 34 F4.2 Jy/beam Speak [1/8.4] Peak brightness (2)
36- 39 F4.2 Jy/beam e_Speak [0.01/1.4] Uncertainty in Speak
41 A1 --- l_d Limit flag on d
43- 47 F5.2 mas d [0.06/1.3] Size of the core component (2)
49- 52 F4.2 mas e_d [0/0.6]? Uncertainty in d
54 A1 --- l_Tb Limit flag on Tb
56- 61 F6.2 10+9K Tb [0.49/267.6] Measured brightness temperature
63- 66 F4.2 10+9K e_Tb [0.01/3.4]? Uncertainty in Tb
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Note (2): For the core component at the center of the image.
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Global notes:
Note (G1): Observing frequency band as follows:
K = 22GHz band
Q = 43GHz band
W = 86GHz band
D = 129GHz band
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Apr-2022