Paper

A Late-Time Radio Flare following a Possible Transition in Accretion State in the Tidal Disruption Event AT 2019azh

Sfaradi, I, Bright, J, Horesh, A, Green, D A, Williams, D R A, Fender, R, Schulze, S

2022

Overview

We report here radio follow-up observations of the optical Tidal Disruption Event (TDE) AT 2019azh. Previously reported X-ray observations of this TDE showed variability at early times and a dramatic increase in luminosity, by a factor of \\(\\sim 10\\), about 8 months after optical discovery. The X-ray emission is mainly dominated by intermediate hard--soft X-rays and is exceptionally soft around the X-ray peak, which is \\(L_X \\sim 10^{43} \\rm \\, erg \\, s^{-1}\\). The high cadence \\(15.5\\) GHz observations reported here show an early rise in radio emission followed by an approximately constant light curve, and a late-time flare. This flare starts roughly at the time of the observed X-ray peak luminosity and reaches its peak about \\(110\\) days after the peak in the X-ray, and a year after optical discovery. The radio flare peaks at \\(\\nu L_{\\nu} \\sim 10^{38} \\rm \\, erg \\, s^{-1}\\), a factor of two higher than the emission preceding the flare. In light of the late-time radio and X-ray flares, and the X-ray spectral evolution, we speculate a possible transition in the accretion state of this TDE, similar to the observed behavior in black hole X-ray binaries. We compare the radio properties of AT 2019azh to other known TDEs, and focus on the similarities to the late time radio flare of the TDE ASASSN-15oi.

• Publisher: Cornell University Library, arXiv.org
• Subject: Black holes / Deposition / Disruption / Light curve / Luminosity / Radio emission / Soft x rays / X ray binaries / X ray spectra / X ray stars / X-ray astronomy / X-rays