Kavli Affiliate: Erin Kara
| First 5 Authors: Yuhan Yao, Muryel Guolo, Francesco Tombesi, Ruancun Li, Suvi Gezari
| Summary:
We present the tidal disruption event (TDE) AT2022lri, hosted in a nearby
($approx!144$ Mpc) quiescent galaxy with a low-mass massive black hole
($10^4,M_odot < M_{rm BH} < 10^6,M_odot$). AT2022lri belongs to the
TDE-H+He subtype. More than 1 Ms of X-ray data were collected with NICER,
Swift, and XMM-Newton from 187 d to 672 d after peak. The X-ray luminosity
gradually declined from $1.5times 10^{44},{rm erg,s^{-1}}$ to $1.5times
10^{43},{rm erg,s^{-1}}$ and remains much above the UV and optical
luminosity, consistent with a super-Eddington accretion flow viewed face-on.
Sporadic strong X-ray dips atop a long-term decline are observed, with
variability timescale of $approx!0.5$ hr–1 d and amplitude of
$approx!2$–8. When fitted with simple continuum models, the X-ray spectrum
is dominated by a thermal disk component with inner temperature going from
$sim! 146$ eV to $sim! 86$ eV. However, there are residual features that
peak around 1 keV, which, in some cases, cannot be reproduced by a single broad
emission line. We analyzed a subset of time-resolved spectra with two
physically motivated models describing either a scenario where ionized
absorbers contribute extra absorption and emission lines or where disk
reflection plays an important role. Both models provide good and statistically
comparable fits, show that the X-ray dips are correlated with drops in the
inner disk temperature, and require the existence of sub-relativistic
(0.1–0.3$c$) ionized outflows. We propose that the disk temperature
fluctuation stems from episodic drops of the mass accretion rate triggered by
magnetic instabilities or/and wobbling of the inner accretion disk along the
black hole’s spin axis.
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