A Late-time Radio Flare Following a Possible Transition in Accretion State in the Tidal Disruption Event AT 2019azh
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Publication Date
2022Journal Title
Astrophysical Journal
ISSN
0004-637X
Publisher
American Astronomical Society
Type
Article
This Version
AM
Metadata
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Sfaradi, I., Horesh, A., Fender, R., Green, D., Williams, D., Bright, J., & Schulze, S. (2022). A Late-time Radio Flare Following a Possible Transition in Accretion State in the Tidal Disruption Event AT 2019azh. Astrophysical Journal https://doi.org/10.3847/1538-4357/ac74bc
Abstract
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.
Keywords
astro-ph.HE, astro-ph.HE
Sponsorship
European Research Council (307215)
Identifiers
External DOI: https://doi.org/10.3847/1538-4357/ac74bc
This record's URL: https://www.repository.cam.ac.uk/handle/1810/337652
Rights
Publisher's own licence
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