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PKS 1954-388: RadioAstron detection on 80,000 km baselines and multiwavelength observations
journal contribution
posted on 2023-05-19, 13:21 authored by Edwards, PG, Kovalev, YY, Ojha, R, An, H, Bignall, H, Carpenter, B, Hovatta, T, Stevens, J, Voytsik, P, Andrianov, AS, Dutka, M, Hase, H, Horiuchi, S, Jauncey, DL, Kadler, M, Lisakov, M, James LovellJames Lovell, Jamie McCallumJamie McCallum, Mueller, C, Phillips, C, Plotz, C, Quick, J, Reynolds, C, Schulz, R, Sokolovsky, KV, Tzioumis, AK, Zuga, VWe 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.
Funding
Department of Industry, Science, Energy and Resources
Geoscience Australia
History
Publication title
Publications of the Astronomical Society of AustraliaVolume
34Article number
e021Number
e021Pagination
1-10ISSN
1323-3580Department/School
School of Natural SciencesPublisher
C S I R O PublishingPlace of publication
150 Oxford St, Po Box 1139, Collingwood, Australia, Victoria, 3066Rights statement
© Astronomical Society of Australia 2017Repository Status
- Restricted