J/MNRAS/402/2087 Optical polarization of OJ 287 in 2005-2009 (Villforth+, 2010)
Variability and stability in blazar jets on time scales of years:
Optical polarization monitoring of OJ 287 in 2005-2009.
Villforth C., Nilsson K., Heidt J., Takalo L.O., Pursimo T., Berdyugin A.,
Lindfors E., Pasanen M., Winiarski M., Drozdz M., Ogloza W.,
Kurpinska-Winiarska M., Siwak M., Koziel-Wierzbowska D., Porowski C.,
Kuzmicz A., Krzesinski J., Kundera T., Wu J.-H., Zhou X., Efimov Y.,
Sadakane K., Kamada M., Ohlert J., Hentunen V.-P., Nissinen M.,
Dietrich M., Assef R.J., Atlee D.W., Bird J., DePoy D.L., Eastman J.,
Peeples M.S., Prieto J., Watson L., Yee J.C., Liakos A., Niarchos P.,
Gazeas K., Dogru S., Donmez A., Marchev D., Coggins-Hill S.A.,
Mattingly A., Keel W.C., Haque S., Aungwerojwit A., Bergvall N.
<Mon. Not. R. Astron. Soc. 402, 2087 (2010)>
=2010MNRAS.402.2087V 2010MNRAS.402.2087V
ADC_Keywords: BL Lac objects ; Polarization ; Photometry, UBVRI ;
Photometry, SDSS
Keywords: accretion, accretion discs - magnetic fields - polarization -
shock waves - BL Lacertae objects: individual: OJ 287 -
galaxies : jets
Abstract:
OJ287 is a BL Lac object at redshift z=0.306 that has shown
double-peaked bursts at regular intervals of ∼12yr during the last
∼40yr. We analyse optical photopolarimetric monitoring data from
2005-2009, during which the latest double-peaked outburst occurred.
The aim of this study is twofold: firstly, we aim to analyse
variability patterns and statistical properties of the optical
polarization light-curve. We find a strong preferred position angle in
optical polarization. The preferred position angle can be explained by
separating the jet emission into two components: an optical
polarization core and chaotic jet emission. The optical polarization
core is stable on time scales of years and can be explained as
emission from an underlying quiescent jet component. The chaotic jet
emission sometimes exhibits a circular movement in the Stokes plane.
We find six such events, all on the timescales of 10-20days. We
interpret these events as a shock front moving forwards and backwards
in the jet, swiping through a helical magnetic field. Secondly, we use
our data to assess different binary black hole models proposed to
explain the regularly appearing double-peaked bursts in OJ287. We
compose a list of requirements a model has to fulfil to explain the
mysterious behaviour observed in OJ287. The list includes not only
characteristics of the light-curve but also other properties of OJ287,
such as the black hole mass and restrictions on accretion flow
properties. We rate all existing models using this list and conclude
that none of the models is able to explain all observations. We
discuss possible new explanations and propose a new approach to
understanding OJ287. We suggest that both the double-peaked bursts and
the evolution of the optical polarization position angle could be
explained as a sign of resonant accretion of magnetic field lines, a
'magnetic breathing' of the disc.
Description:
These files present the observational data of the paper. There are 7
files : 6 for photometry (BVRIri) and one for polarimetry. Details of
the reduction procedures and the telescopes involved can be found in
the paper.
Objects:
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RA (2000) DE Designation(s)
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08 54 48.9 +20 06 31 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
bband.dat 34 139 B-band photometry of OJ 287
vband.dat 34 315 V-band photometry of OJ 287
rband.dat 34 1473 R-band photometry of OJ 287
iband.dat 34 244 I-band photometry of OJ 287
sdssr.dat 34 38 SDSS r-band photometry of OJ 287
sdssi.dat 34 24 SDSS i-band photometry of OJ 287
polarim.dat 79 400 Polarimetry of OJ 287
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See also:
J/A+AS/129/569 : BVRI photometry of OJ 287 (Jia Guibin+ 1998)
J/AJ/132/1256 : eim BATC photometry of OJ 287 (Wu+, 2006)
J/MNRAS/385/823 : UBVRI light curves of OJ 287 (Zheng+, 2008)
Byte-by-byte Description of file: ?band.dat dat sdss?.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 F13.5 d JD Julian Date
15 A1 --- Band [BVRIri] Filter
17- 22 F6.3 mag mag Apparent magnitude (1)
25- 29 F5.3 mag e_mag Magnitude error
32- 34 A3 --- Tel Telescope used (2)
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Note (1): Not corrected for the galactic extinction or host galaxy.
Note (2): Key to the telescope abbreviations:
ATH = Athens, Greece
CA = Calar Alto, Spain
CO = Canakkale, Turkey
GC = Grove Creek, Australia
HEI = Heidelberg, Germany
KR = Krakow, Poland
MDM = MDM, USA
KVA = KVA, La Palma
LIV = Liverpool telescope, La Palma
NOT = NOT, La Palma
OSA = Osaka, Japan
SAT = St. Augustine - Tuorla, Trinidad
SUH = Mt. Suhora, Poland
TH = Taurus Hill, Finland
TRE = Trebur, Germany
TUO = Tuorla, Finland
UA = University of Alabama, USA
XIO = Xinglong, China
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Byte-by-byte Description of file: polarim.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d JD Julian Date
15- 17 A3 --- Tel Telescope used (1)
19- 21 I3 --- N Number of points averaged
23- 29 F7.3 % PQ Normalized Stokes parameter PQ
32- 36 F5.3 % e_PQ rms uncertainty on PQ
38- 44 F7.3 % PU Normalized Stokes parameter PU
47- 51 F5.3 % e_PU rms uncertainty on PU
53 A1 --- l_Pol Limit flag on Pol
54- 59 F6.3 % Pol Degree of polarization
62- 66 F5.3 % e_Pol rms uncertainty on Pol
69- 73 F5.1 deg PA Position angle of the polarization vector
76- 79 F4.1 deg e_PA rms uncertainty on PA
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Note (1): Key to telescope abbreviations. Note that the telescope fixes
also the filter as indicated:
CA = Calar Alto 2.2m telescope, Spain, R-band
KVA = KVA telescope, La Palma, no filter ("white light")
NOT = Nordic Optical Telescope, La Palma, R-band
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Acknowledgements:
Kari Nilsson, kari.nilsson(at)utu.fi
(End) Kari Nilsson [Tuorla Observatory], Patricia Vannier [CDS] 23-Feb-2010