Kavli Affiliate: Erin Kara
| Summary:
We present a five-year X-ray spectral and timing analysis of the optically selected Tidal Disruption Event (TDE) AT2019teq, which displays extreme variability, including order-of-magnitude changes in flux on minute-to-day timescales, and a rare late-time emergence of hard X-ray emission leading to the longest-lived corona in a known TDE. In one epoch, we detect sub-mHz quasi-periodic oscillations with significance tested via MCMC-based red-noise simulations (p $leq 0.03$). AT2019teq exhibits a clear spectral evolution from a soft (blackbody-dominated) state to a hard (power-law-dominated) state, with a late-time radio brightening that may be associated with the state transition. We identify similarities between AT2019teq’s evolution and X-ray binary soft-to-hard state transitions, albeit at higher luminosity and much faster timescales. We use the presence of both a disk-dominated and a corona-dominated state to apply multiple mass estimators from X-ray spectral and variability properties. These techniques are mutually consistent within $2σ$ and systematically yield a lower black hole mass ($log(M_BH/M_odot) = 5.67 pm 0.09$) than inferred from host galaxy scaling ($log(M_BH/M_odot)=6.14 pm 0.19$).
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