J/ApJ/862/1 Rotation reversals in the polarization in OJ 287 (Cohen+, 2018)
Reversals in the direction of polarization rotation in OJ 287.
Cohen M.H., Aller H.D., Aller M.F., Hovatta T., Kharb P., Kovalev Y.Y.,
Lister M.L., Meier D.L., Pushkarev A.B., Savolainen T.
<Astrophys. J., 862, 1 (2018)>
=2018ApJ...862....1C 2018ApJ...862....1C
ADC_Keywords: Polarization; BL Lac objects; Radio continuum
Keywords: BL Lacertae objects: individual (OJ 287) ; galaxies: jets ;
magnetohydrodynamics (MHD) ; polarization ; radio continuum: galaxies
Abstract:
We have obtained a smooth time series for the electric vector position
angle (EVPA) of the blazar OJ 287 at centimeter wavelengths, by making
±nπ adjustments to archival values from 1974 to 2016. The data
display rotation reversals in which the EVPA rotates counterclockwise
for ∼180° and then rotates clockwise by a similar amount. The
timescale of the rotations is a few weeks to a year, and the scale for
a double rotation, including the reversal, is 1-3yr. We have seen four
of these events in 40yr. A model consisting of two successive
outbursts in polarized flux density, with EVPAs counterrotating,
superposed on a steady polarized jet, can explain many of the details
of the observations. Polarization images support this interpretation.
The model can also help to explain similar events seen at optical
wavelengths. The outbursts needed for the model can be generated by
the supermagnetosonic jet model of Nakamura+ (2010ApJ...721.1783N 2010ApJ...721.1783N) and
Nakamura & Meier (2014ApJ...785..152N 2014ApJ...785..152N), which requires a strong
helical magnetic field. This model produces forward and reverse pairs
of fast and slow MHD waves, and the plasma inside the two fast/slow
pairs rotates around the jet axis, but in opposite directions.
Description:
The archives of the University of Michigan Radio Astronomy Observatory
(UMRAO) provide measurements of flux density (F) and polarized flux
density that were made every few days with a 26m dish and span the
years 1975-2012.
We also use data from the MOJAVE program (Monitoring of Jets in Active
Galactic Nuclei with VLBA Experiments), which includes archival data
back to 1995. This is a continuing program, and for this paper we stop
at 2016.0. MOJAVE uses the VLBA at 15.3GHz.
We have also used results obtained by other VLBA observers at 15.3 or
15.4GHz and placed in the VLBA archive. In these cases the data have
been reprocessed by the MOJAVE team, to make a homogeneous data set.
In addition to the UMRAO and VLBA data, we use the results of Kikuchi+
(1988A&A...190L...8K 1988A&A...190L...8K), who made polarization observations of OJ 287 at
several frequencies ranging from 9.0 to 10.5GHz, for 6 months in 1986.
The data were taken with the 45m dish at Nobeyama.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
08 54 48.87 +20 06 30.6 OJ 287 = OHIO J 287
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 32 2980 University of Michigan Radio Astronomy Observatory
(UMRAO) single dish data
table2.dat 23 93 MOJAVE 15GHz VLBA core feature data
table3.dat 25 19 Kikuchi+ (1988A&A...190L...8K 1988A&A...190L...8K) 10GHz radio data
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See also:
J/A+AS/39/379 : Linear Polarization of radio sources (Tabara+ 1980)
J/AJ/87/859 : Polarisation of 404 radio sources at 6 and 20cm (Perley, 1982)
J/A+AS/129/569 : BVRI photometry of OJ 287 (Jia Guibin+ 1998)
J/A+AS/139/545 : 1-22 GHz spectra survey (Kovalev+, 1999)
J/ApJ/522/846 : Optical monitoring of GeV loud blazars (Xie+, 1999)
J/A+A/441/915 : Alignments of quasar polarization vectors (Hutsemekers+, 2005)
J/AJ/130/1418 : AGN jet kinematics (Jorstad+, 2005)
J/AJ/130/1389 : Linear polarization of AGN jets at 15GHz (Lister+, 2005)
J/AJ/131/1262 : Circ. polarization images at 15GHz of AGN jets (Homan+, 2006)
J/AJ/132/1256 : eim BATC photometry of OJ 287 (Wu+, 2006)
J/AJ/133/1947 : 37GHz observations of BL Lac objects (Nieppola+, 2007)
J/AJ/134/799 : Multiwaveband polarimetry of 15 AGN (Jorstad+, 2007)
J/MNRAS/380/162 : Aligned radio polarizations of quasars (Joshi+, 2007)
J/MNRAS/385/823 : UBVRI light curves of OJ 287 (Zheng+, 2008)
J/AJ/137/3718 : 15GHz monitoring of AGN jets with VLBA (Lister+, 2009)
J/MNRAS/402/2087 : Opt. polarization of OJ 287 in 2005-2009 (Villforth+, 2010)
J/ApJS/189/1 : A 3.5mm polarimetric survey of radio-loud AGNs (Agudo+, 2010)
J/ApJS/194/19 : Optical linear polarization at McDonald Obs. (Wills+, 2011)
J/AJ/141/65 : BATC ceimo light curves of OJ 287 (Dai+, 2011)
J/MNRAS/421/1861 : OJ287 polarization and VLBI jet direction (Valtonen+, 2012)
J/ApJ/747/63 : 7mm VLBA observations of BL Lac object OJ287 (Agudo+, 2012)
J/ApJ/764/5 : BR photom. of 2012 precursor flare in OJ287 (Pihajoki+, 2013)
J/AJ/146/120 : MOJAVE. X. Parsec-scale kinematics of AGNs (Lister+, 2013)
J/A+A/559/A20 : Historical outbursts of OJ287 (Hudec+, 2013)
J/ApJ/787/151 : Fitted jet components in BL Lacertae (Cohen+, 2014)
J/MNRAS/442/1693 : Gamma-ray-loud blazars opt. polarization (Pavlidou+, 2014)
J/A+A/566/A59 : 3.5 & 1.3mm pol. survey of Northern AGNs (Agudo+, 2014)
J/ApJS/212/15 : Polarized NVSS sources SEDs (Farnes+, 2014)
J/A+A/596/A45 : Radio light curves of 8 AGN (Fuhrmann+, 2016)
J/A+A/590/A10 : 3C 279 optical photometry and polarimetry (Kiehlmann+, 2016)
J/AJ/152/12 : MOJAVE. XIII. New 15GHz obs. on 1994-2013 (Lister+, 2016)
J/ApJ/833/77 : gamma-ray bright blazars optical polarization (Itoh+, 2016)
J/ApJ/835/275 : OJ287 flux+polarization during 2016 outburst (Rakshit+, 2017)
J/ApJ/846/98 : Jet kinematics of blazars at 43GHz with VLBA (Jorstad+, 2017)
J/A+A/597/A80 : GMVA 86GHz images of OJ 287 (Hodgson+, 2017)
J/ApJS/234/12 : MOJAVE XV. VLBA 15GHz obs. of AGN jets (Lister+, 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/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- 8 F8.3 yr Date [1971.3/2012.5] Observation epoch, fractional year
10- 13 F4.1 GHz nu [4.8/14.5] Observation frequency
15- 19 F5.2 Jy Ftot [1/10.4] Total flux density
21- 24 F4.1 % Pol [0.4/17.5] Fractional linear polarization
26- 32 F7.1 deg EVPA [-1000/202.5] Adjusted electric vector
position angle
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.3 yr Date [1996/2015.6] Observation epoch, fractional year
10- 13 F4.2 Jy/beam I [0.86/5.96] Stokes I intensity
15- 18 F4.1 % Pol [0.2/10.8] Fractional linear polarization
20- 23 I4 deg EVPA [-90/198] Adjusted electric vector
position angle
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 yr Date [1986/1986.5] Observation Epoch, fractional year
10- 13 F4.2 Jy Ftot [0.2/2.7]? Total flux density at 10GHz
15- 18 F4.2 % Pol [3.5/7.2]? Fractional linear polarization
20- 25 F6.1 deg EVPA [-206/108]? Adjusted electric vector
position angle
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [AAS] 17-Jul-2019