J/A+A/597/A80 GMVA 86GHz images of OJ 287 (Hodgson+, 2017)
Location of gamma-ray emission and magnetic field strengths in OJ 287.
Hodgson J.A., Krichbaum T.P., Marscher A.P., Jorstad S.G., Rani B.,
Marti-Vidal I., S.Sanchez, Bremer M., Lindqvist M., Uunila M., Kallunki J.,
Vicente P., Angelakis E., Karamanavis V., Myserlis I., Nestoras I.,
Sievers A., Gurwell M., Zensus J.A.
<Astron. Astrophys. 597, A80 (2017)>
=2017A&A...597A..80H 2017A&A...597A..80H (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Gamma rays
Keywords: BL Lacertae objects: individual: OJ 287 - galaxies: active -
magnetic fields - techniques: high angular resolution -
techniques: interferometric - galaxies: jets
Abstract:
The gamma-ray BL Lac object OJ 287 is known to exhibit inner-parsec
"jet-wobbling", high degrees of variability at all wavelengths and
quasi-stationary features, including an apparent (∼100°)
position-angle change in projection on the sky plane.
Sub-50 micro-arcsecond resolution 86GHz observations with the global
mm-VLBI array (GMVA) supplement ongoing multifrequency VLBI blazar
monitoring at lower frequencies. Using these maps, together with cm/mm
total intensity and gamma-ray observations from Fermi/LAT from
2008-2014, we aim to determine the location of gamma-ray emission and
to explain the inner-mas structural changes.
Observations with the GMVA offset approximately double the angular
resolution compared with 43GHz VLBA observations and enable us to
observe above the synchrotron self-absorption peak frequency.
Fermi-LAT gamma-ray data were reduced and analysed. The jet was
spectrally decomposed at multiple locations along the jet. From this,
we could derive estimates of the magnetic field using equipartition
and synchrotron self-absorption arguments. How the field decreases
down the jet provided an estimate of the distance to the jet apex and
an estimate of the magnetic field strength at the jet apex and in the
broad line region. Combined with accurate kinematics, we attempt to
locate the site of gamma-ray activity, radio flares, and spectral
changes.
Description:
The GMVA combines the eight 3mm receiver equipped stations
of the VLBA and up to six European observatories, including
Elsberg, Onsala, Metsahovi, Pico Veleta, Plateau de Bure, and
since 2012, Yebes. Data were recorded at 512 Mbit/s, with eight 8MHz
channels, in dual polarisation. Onsala and Yebes observed in left
circular polarisation (LCP) only. For these stations, LCP was assumed
to be equal to RCP and hence Stokes I. Scans of approximately 7
minutes every 15 minutes were recorded with pointing and calibration
performed on European stations in the gaps between scans.
Objects:
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RA (2000) 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
list.dat 112 7 List of fits images
fits/* . 7 Individual fits images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 39 A10 "date" Obs.Date Observation date
41- 47 F7.4 GHz Freq [86.2349/86.2429] Observed frequency
49- 53 I5 Kibyte size Size of FITS file
55- 77 A23 --- FileName Name of FITS file, in subdirectory fits
79-112 A34 --- Title Title of the FITS file
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Acknowledgements:
Jeffrey Hodgson, jhodgson(at)kasi.re.kr
(End) Patricia Vannier [CDS] 05-Jan-2017