Paper

Late-time radio brightening and emergence of a radio jet in the changing-look AGN 1ES 1927+654

Sadaula, Dev R, Oates, Samantha, Bempong-Manful, Emmanuel K, Hankla, Amelia M, Mbarek, Rostom, Guainazzi, Matteo, S Bradley Cenko, Bray, Justin D, Meyer, Eileen T, Nicholl, Matt, Behar, Ehud, Gurwell, Mark A, Ricci, Federica, Bianchi, Stefano, Laha, Sibasish, Williams-Baldwin, David, Georganopoulos, Markos, Wrigley, Nicholas, Yang, Xiaolong, Keating, Garrett K, Roychowdhury, Agniva, laor, Ari, Zhang, Haocheng, Philippov, Alexander, Panessa, Francesca, Kara, Erin, Begelman, Mitchell C, Ghosh, Ritesh, Masterson, Megan, Shuvo, Onic I, Main Pal, Fabio La Franca, Rhodes, Lauren, Bruni, Gabriele, Green, David A

2024

Overview

We present multi-frequency (5-345 GHz) and multi-resolution radio observations of 1ES 1927+654, widely considered one of the most unusual and extreme changing-look active galactic nuclei (CL-AGN). The source was first designated a CL-AGN after an optical outburst in late 2017 and has since displayed considerable changes in X-ray emission, including the destruction and rebuilding of the X-ray corona in 2019-2020. Radio observations prior to 2023 show a faint and compact radio source typical of radio-quiet AGN. Starting in February 2023, 1ES 1927+654 began exhibiting a radio flare with a steep exponential rise, reaching a peak 60 times previous flux levels, and has maintained this higher level of radio emission for over a year to date. The 5-23 GHz spectrum is broadly similar to gigahertz-peaked radio sources, which are understood to be young radio jets less than ~1000 years old. Recent high-resolution VLBA observations at 23.5 GHz now show resolved extensions on either side of the core, with a separation of ~0.15 pc, consistent with a new and mildly relativistic bipolar outflow. A steady increase in the soft X-ray band (0.3-2 keV) concurrent with the radio may be consistent with jet-driven shocked gas, though further observations are needed to test alternate scenarios. This source joins a growing number of CL-AGN and tidal disruption events which show late-time radio activity, years after the initial outburst.

• Publisher: Cornell University Library, arXiv.org
• Subject: Active galactic nuclei / Outbursts / Radio emission / Radio jets (astronomy) / Radio observation / Radio sources (astronomy) / Soft x rays