2020/09/01 by Steven J. Tingay, Steven Tingay, James C. A. Miller-Jones +2 · 2 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Event (particle physics) #Flux (metallurgy) #Interpretation (philosophy) #Luminosity #Outflow #Pulsars and Gravitational Waves Research #Transient (computer programming) #Very Long Baseline Array #Very-long-baseline interferometry #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.3847/2041-8213/abb60d
published in The Astrophysical Journal Letters 901(1), L17 (IOP Publishing) · Eight pages, three figures, accepted to ApJ Letters
openalex publication_date 2020/09/01 · arxiv created 2020/09/08 · openalex created_date 2020/09/14 · arxiv updated 2020/09/30 · openalex updated_date 2026/08/06
Abstract We have analyzed archival Very Long Baseline Array (VLBA) data for Cygnus A between 2002 and 2013, to search for radio emission from the transient discovered in 2015 by Perley et al. approximately 0.″4 from the nucleus of Cygnus A (Cyg A-2). Perley et al. use Very Large Array and VLBA archival data (between 1989 and 1997) to show that the transient rises in flux density by a factor of at least 5 in less than approximately 20 yr. With the additional data presented here, we revise the rise time to between approximately 4 and 6 yr, based on a new detection of the source at 15.4 GHz from 2011 October. Our results strengthen the interpretation of Cyg A-2 as the result of a tidal disruption event (TDE), as we can identify the location of the compact object responsible for the TDE and can estimate the angular expansion speed of the resulting radio-emitting structures, equivalent to an apparent expansion speed of <0.9 c . While our results are consistent with recent X-ray analyses, we can rule out a previously suggested date of early 2013 for the timing of the TDE. We favor a timing between early 2009 and late 2011. Applying the model of Nakar & Piran, we suggest a TDE causing a mildly relativistic outflow with a (density-dependent) total energy >10 49 erg. Due to the improved temporal coverage of our archival measurements, we find that it is unlikely that Cyg A-2 has previously been in a high luminosity radio state over the last 30 yr.