PKS 1954–388: RadioAstron detection on 80,000 km baselines and multiwavelength observations
- CSIRO Astronomy and Space Science, Epping, NSW (Australia)
- Astro Space Center of Lebedev Physical Institute, Moscow (Russia)
- NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Catholic Univ. of America, Washington, D.C. (United States); Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States)
- Stanford Univ., Stanford, CA (United States); Chungbuk National Univ., Cheongju (Republic of Korea)
- NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Catholic Univ. of America, Washington, D.C. (United States)
- Aalto Univ. Metsahovi Radio Observatory, Kylmala (Finland); Aalto Univ. Dept. of Radio Science and Engineering, Aalto (Finland).
- Bundesamt fur Kartographie und Geodasie, Bad Kotzting (Germany)
- CSIRO Astronomy and Space Science, ACT (Australia)
- CSIRO Astronomy and Space Science, Epping, NSW (Australia); Australian National Univ., Canberra, ACT (Australia)
- Univ. Wurzburg, Wurzburg (Germany)
- Univ. of Tasmania, Hobart, TAS (Australia)
- Radboud Univ. Nijmegen, Nijmegen (The Netherlands)
- Australian National Univ., Canberra, ACT (Australia)
- Hartebeesthoek Radio Astronomy Observatory, Krugersdorp (South Africa)
- ASTRON The Netherlands Institute for Radio Astronomy, Dwingeloo (The Netherlands)
- Astro Space Center of Lebedev Physical Institute, Moscow (Russia); National Observatory of Athens, Penteli (Greece); Moscow State Univ., Moscow (Russia)
Here, 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.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC02-76SF00515
- OSTI ID:
- 1355732
- Journal Information:
- Publications of the Astronomical Society of Australia, Vol. 34; ISSN 1323-3580
- Publisher:
- CSIROCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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