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PKS 1954-388: RadioAstron detection on 80,000 km baselines and multiwavelength observations


Edwards, PG and Kovalev, YY and Ojha, R and An, H and Bignall, H and Carpenter, B and Hovatta, T and Stevens, J and Voytsik, P and Andrianov, AS and Dutka, M and Hase, H and Horiuchi, S and Jauncey, DL and Kadler, M and Lisakov, M and Lovell, JEJ and McCallum, J and Mueller, C and Phillips, C and Plotz, C and Quick, J and Reynolds, C and Schulz, R and Sokolovsky, KV and Tzioumis, AK and Zuga, V, PKS 1954-388: RadioAstron detection on 80,000 km baselines and multiwavelength observations, Publications of the Astronomical Society of Australia, 34 Article e021. ISSN 1323-3580 (2017) [Refereed Article]

Copyright Statement

© Astronomical Society of Australia 2017

DOI: doi:10.1017/pasa.2017.16


We present results from a multiwavelength study of the blazar PKS 1954–388 at radio, UV, X-ray, and gamma-ray energies. A RadioAstron observation at 1.66 GHz in June 2012 resulted in the detection of interferometric fringes on baselines of 6.2 Earth-diameters. This suggests a source frame brightness temperature of greater than 2 × 1012 K, well in excess of both equipartition and inverse Compton limits and implying the existence of Doppler boosting in the core. An 8.4-GHz TANAMI VLBI image, made less than a month after the RadioAstron observations, is consistent with a previously reported superluminal motion for a jet component. Flux density monitoring with the Australia Telescope Compact Array confirms previous evidence for long-term variability that increases with observing frequency. A search for more rapid variability revealed no evidence for significant day-scale flux density variation. The ATCA light-curve reveals a strong radio flare beginning in late 2013, which peaks higher, and earlier, at higher frequencies. Comparison with the Fermi gamma-ray light-curve indicates this followed ∼9 months after the start of a prolonged gamma-ray high-state—a radio lag comparable to that seen in other blazars. The multiwavelength data are combined to derive a Spectral Energy Distribution, which is fitted by a one-zone synchrotron-self-Compton (SSC) model with the addition of external Compton (EC) emission.

Item Details

Item Type:Refereed Article
Keywords:galaxies: active, galaxies: jets, gamma rays: galaxies, ISM: structure, radio continuum: galaxies
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Cosmology and extragalactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Lovell, JEJ (Dr Jim Lovell)
UTAS Author:McCallum, J (Dr Jamie McCallum)
ID Code:122314
Year Published:2017
Web of Science® Times Cited:1
Deposited By:Mathematics and Physics
Deposited On:2017-11-09
Last Modified:2018-08-28

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