APPARENT INWARD MOTION OF THE PARSEC-SCALE JET IN THE BL LAC OBJECT OJ287 DURING THE 2011-2012 γ-ray FLARES

Sawada-Satoh, Satoko; Akiyama, Kazunori; Niinuma, Kotaro; Nagai, Hiroshi; Kino, Motoki; D’Ammando, F.; Koyama, Shoko; Hada, Kazuhiro; Orienti, M.; Honma, Mareki; Shibata, Katsunori M.

doi:10.5303/pkas.2015.30.2.429

Cited by 3 publications

(1 citation statement)

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“…Gamma-ray emission was suggested to be correlated with mm-radio flaring and placed at least 14 pc away from the central engine, largely in agreement with spectral energy distribution (SED) modelling by Kushwaha et al (2013). Recent flaring activity in 2011-2012 was analysed by Sawada-Satoh et al (2015) using 22 GHz VLBI maps. They interpreted the γ-ray flaring as possibly being a new jet component that is unresolved at 22 GHz.…”

Section: Introductionmentioning

confidence: 99%

Location ofγ-ray emission and magnetic field strengths in OJ 287

Hodgson

Krichbaum

Marscher

et al. 2017

A&A

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Context. The γ-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. Aims. Sub-50 micro-arcsecond resolution 86 GHz 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 γ-ray observations from Fermi/LAT from 2008-2014, we aimed to determine the location of γ-ray emission and to explain the inner-mas structural changes. Methods. Observations with the GMVA offer approximately double the angular resolution compared with 43 GHz VLBA observations and allow us to observe above the synchrotron self-absorption peak frequency. Fermi-LAT γ-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 allowed 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 γ-ray activity, radio flares and spectral changes. Results. Strong γ-ray flares appeared to originate from either the "core" region, a downstream stationary feature, or both, with γ-ray activity significantly correlated with radio flaring in the downstream quasi-stationary feature. Magnetic field estimates were determined at multiple locations along the jet, with the magnetic field found to be ≥ 1.6 G in the "core" and ≤ 0.4 G in the downstream quasi-stationary feature. We therefore found upper limits on the location of the VLBI "core" as 6.0 pc from the jet apex and determined an upper limit on the magnetic field near the jet base of the order of thousands of Gauss.

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Section: Introductionmentioning

confidence: 99%

Location ofγ-ray emission and magnetic field strengths in OJ 287

Hodgson

Krichbaum

Marscher

et al. 2017

A&A

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On the Epistemology of Observational Black Hole Astrophysics

Doboszewski¹,

Lehmkuhl²

2023

Synthese Library

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We discuss three philosophically interesting epistemic peculiarities of black hole astrophysics: (1) issues concerning whether and in what sense black holes do exist; (2) how to best approach multiplicity of available definitions of black holes; (3) short (i.e., accessible within an individual human lifespan) dynamical timescales present in many of the recent, as well as prospective, observations involving black holes. In each case we argue that the prospects for our epistemic situation are optimistic.

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Parsec-scale evolution of the gigahertz-peaked spectrum quasar PKS 0858 − 279

Kosogorov,

Kovalev,

Perucho

et al. 2024

Monthly Notices of the Royal Astronomical Society

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We conducted multi-epoch, multi-frequency parsec-scale studies on the gigahertz-peaked spectrum quasar PKS 0858−279 with the Very Long Baseline Array (VLBA). Our observations on 2005-11-26 elucidated a weak core, characterized by an inverted spectrum, and a distinctly bent jet that exhibited a notable bright feature in its Stokes I emission. Through comprehensive analysis of polarization and spectral data, we inferred the formation of a shock wave within this feature, stemming from interactions with a dense cloud in the ambient medium. In this paper, VLBI-Gaia astrometry further reinforces the core identification. With a deep analysis of six additional VLBA epochs spanning from 2007 to 2018, we observed that while the quasar’s parsec-scale structure remained largely consistent, there were discernible flux density changes. These variations strongly imply the recurrent ejection of plasma into the jet. Complementing our VLBA data, RATAN-600 observations of the integrated spectra suggested an interaction between standing and travelling shock waves in 2005. Moreover, our multi-epoch polarization analysis revealed a drastic drop in rotation measure values from 6000 rad/m2 to 1000 rad/m2 within a single year, attributable to diminishing magnetic fields and particle density in an external cloud. This change is likely instigated by a shock in the cloud, triggered by the cloud’s interaction with the jet, subsequently prompting its expansion. Notably, we also observed a significant change in the magnetic field direction of the jet, from being perpendicular post its observed bend to being perpendicular prior to the bend – an alteration possibly induced by the dynamics of shock waves.

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APPARENT INWARD MOTION OF THE PARSEC-SCALE JET IN THE BL LAC OBJECT OJ287 DURING THE 2011-2012 γ-ray FLARES

Abstract: We present a kinematic study of the parsec-scale radio jet in OJ 287, one of the most studied BL Lac objects, during γ-ray flares, to explore the relation between parsec-scale radio jet activity and γ-ray emission. The 22-GHz light curve of OJ 287 show three obvious flare events

Cited by 3 publications

References 12 publications

Location ofγ-ray emission and magnetic field strengths in OJ 287

Location ofγ-ray emission and magnetic field strengths in OJ 287

On the Epistemology of Observational Black Hole Astrophysics

Parsec-scale evolution of the gigahertz-peaked spectrum quasar PKS 0858 − 279

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