The brightness temperature problem in extreme intra-day variable quasars: a model for PKS 0405-385
Files
(Published version)
Date
2003
Authors
Protheroe, R.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
Monthly Notices of the Royal Astronomical Society, 2003; 341(1):230-238
Statement of Responsibility
Conference Name
Abstract
I re-examine the brightness temperature problem in PKS 0405-385, which is an extreme intra-day variable radio quasar with an inferred brightness temperature of ∼5 × 10[sup 14] K at 5 GHz, well above the Compton catastrophe limit of ∼10[sup 11] K that is reached when the synchrotron photon energy density exceeds the energy density of the magnetic field. If one takes into account the uncertainty in the distance to the ionized clouds responsible for interstellar scintillation causing rapid intra-day variability in PKS 0405-385, it is possible that the brightness temperature could be as low as ∼10[sup 13] K at 5 GHz, or even lower. The radio spectrum can be fitted by optically thin emission from mono-energetic electrons, or an electron spectrum with a low-energy cut-off such that the critical frequency of the lowest energy electrons is above the radio frequencies of interest. If one observes optically thin emission along a long narrow emission region, the average energy density in the emission region can be many orders of magnitude lower than calculated from the observed intensity if one assumed a spherical emission region. I discuss the physical conditions in the emission region and find that the Compton catastrophe can then be avoided using a reasonable Doppler factor. I also show that MeV to 100-GeV gamma-ray emission at observable flux levels should be expected from extreme intra-day variable sources such as PKS 0405-385
School/Discipline
Dissertation Note
Provenance
Description
Mon.Not.Royal Astronomical Society. All rights reserved. Printed in U.S.A. Submitted to Cornell University’s online archive www.arXiv.org in 2003 by Ray Protheroe. Post-print sourced from www.arxiv.org.
Access Status
Rights
© 2003 RAS