Repository logo

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

Accepted version



Change log


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 ∼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 LX∼1043ergs−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 νLν∼1038ergs−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.



astro-ph.HE, astro-ph.HE

Journal Title

Astrophysical Journal

Conference Name

Journal ISSN


Volume Title


American Astronomical Society


Publisher's own licence
European Research Council (307215)
Swedish Research Council (2016-06012_VR)