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Title: Through the ring of fire: γ-ray variability in blazars by a moving plasmoid passing a local source of seed photons

Abstract

Blazars exhibit flares across the electromagnetic spectrum. Many γ-ray flares are highly correlated with flares detected at optical wavelengths; however, a small subset appears to occur in isolation, with little or no variability detected at longer wavelengths. These “orphan” γ-ray flares challenge current models of blazar variability, most of which are unable to reproduce this type of behavior. We present numerical calculations of the time-variable emission of a blazar based on a proposal by Marscher et al. to explain such events. In this model, a plasmoid (“blob”) propagates relativistically along the spine of a blazar jet and passes through a synchrotron-emitting ring of electrons representing a shocked portion of the jet sheath. This ring supplies a source of seed photons that are inverse-Compton scattered by the electrons in the moving blob. The model includes the effects of radiative cooling, a spatially varying magnetic field, and acceleration of the blob's bulk velocity. Synthetic light curves produced by our model are compared to the observed light curves from an orphan flare that was coincident with the passage of a superluminal knot through the inner jet of the blazar PKS 1510–089. In addition, we present Very Long Baseline Array polarimetric observations that pointmore » to the existence of a jet sheath in PKS 1510–089, thus providing further observational support for the plausibility of our model. An estimate of the bolometric luminosity of the sheath within PKS 1510–089 is made, yielding L{sub sh}∼3×10{sup 45} erg s{sup −1}. This indicates that the sheath within PKS 1510–089 is potentially a very important source of seed photons.« less

Authors:
; ; ;  [1]
  1. Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)
Publication Date:
OSTI Identifier:
22883225
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 804; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; Journal ID: ISSN 0004-637X
Country of Publication:
United Kingdom
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BOLOMETERS; COMPARATIVE EVALUATIONS; ELECTRONS; EMISSION; GALAXIES; LUMINOSITY; MAGNETIC FIELDS; POLARIZATION; RADIATIVE COOLING; RELATIVISTIC RANGE; SEEDS; SPECTRA; SYNCHROTRON RADIATION

Citation Formats

MacDonald, Nicholas R., Marscher, Alan P., Jorstad, Svetlana G., and Joshi, Manasvita. Through the ring of fire: γ-ray variability in blazars by a moving plasmoid passing a local source of seed photons. United Kingdom: N. p., 2015. Web. doi:10.1088/0004-637X/804/2/111.
MacDonald, Nicholas R., Marscher, Alan P., Jorstad, Svetlana G., & Joshi, Manasvita. Through the ring of fire: γ-ray variability in blazars by a moving plasmoid passing a local source of seed photons. United Kingdom. https://doi.org/10.1088/0004-637X/804/2/111
MacDonald, Nicholas R., Marscher, Alan P., Jorstad, Svetlana G., and Joshi, Manasvita. Sun . "Through the ring of fire: γ-ray variability in blazars by a moving plasmoid passing a local source of seed photons". United Kingdom. https://doi.org/10.1088/0004-637X/804/2/111.
@article{osti_22883225,
title = {Through the ring of fire: γ-ray variability in blazars by a moving plasmoid passing a local source of seed photons},
author = {MacDonald, Nicholas R. and Marscher, Alan P. and Jorstad, Svetlana G. and Joshi, Manasvita},
abstractNote = {Blazars exhibit flares across the electromagnetic spectrum. Many γ-ray flares are highly correlated with flares detected at optical wavelengths; however, a small subset appears to occur in isolation, with little or no variability detected at longer wavelengths. These “orphan” γ-ray flares challenge current models of blazar variability, most of which are unable to reproduce this type of behavior. We present numerical calculations of the time-variable emission of a blazar based on a proposal by Marscher et al. to explain such events. In this model, a plasmoid (“blob”) propagates relativistically along the spine of a blazar jet and passes through a synchrotron-emitting ring of electrons representing a shocked portion of the jet sheath. This ring supplies a source of seed photons that are inverse-Compton scattered by the electrons in the moving blob. The model includes the effects of radiative cooling, a spatially varying magnetic field, and acceleration of the blob's bulk velocity. Synthetic light curves produced by our model are compared to the observed light curves from an orphan flare that was coincident with the passage of a superluminal knot through the inner jet of the blazar PKS 1510–089. In addition, we present Very Long Baseline Array polarimetric observations that point to the existence of a jet sheath in PKS 1510–089, thus providing further observational support for the plausibility of our model. An estimate of the bolometric luminosity of the sheath within PKS 1510–089 is made, yielding L{sub sh}∼3×10{sup 45} erg s{sup −1}. This indicates that the sheath within PKS 1510–089 is potentially a very important source of seed photons.},
doi = {10.1088/0004-637X/804/2/111},
url = {https://www.osti.gov/biblio/22883225}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 804,
place = {United Kingdom},
year = {2015},
month = {5}
}