Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Rapid accretion state transitions following the tidal disruption event
  AT2018fyk   Following a tidal disruption event (TDE), the accretion rate can evolve from
quiescent to near-Eddington levels and back over months - years timescales.
This provides a unique opportunity to study the formation and evolution of the
accretion flow around supermassive black holes (SMBHs). We present two years of
multi-wavelength monitoring observations of the TDE AT2018fyk at X-ray, UV,
optical and radio wavelengths. We identify three distinct accretion states and
two state transitions between them. These appear remarkably similar to the
behaviour of stellar-mass black holes in outburst. The X-ray spectral
properties show a transition from a soft (thermal-dominated) to a hard
(power-law dominated) spectral state around L$_{\rm bol} \sim $few $ \times
10^{-2}$ L$_{\rm Edd}$, and the strengthening of the corona over time
$\sim$100--200 days after the UV/optical peak. Contemporaneously, the spectral
energy distribution (in particular, the UV-to-X-ray spectral slope
$\alpha_{ox}$) shows a pronounced softening as the outburst progresses. The
X-ray timing properties also show a marked change, initially dominated by
variability at long ($>$day) timescales while a high frequency ($\sim$10$^{-3}$
Hz) component emerges after the transition into the hard state. At late times
($\sim$500 days after peak), a second accretion state transition occurs, from
the hard into the quiescent state, as identified by the sudden collapse of the
bolometric (X-ray+UV) emission to levels below 10$^{-3.4}$ L$_{\rm Edd}$. Our
findings illustrate that TDEs can be used to study the scale (in)variance of
accretion processes in individual SMBHs. Consequently, they provide a new
avenue to study accretion states over seven orders of magnitude in black hole
mass, removing limitations inherent to commonly used ensemble studies.

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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
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The categories of this paper are: cs
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The categories of this paper are: comp-gas
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The categories of this paper are: physics
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The categories of this paper are: hep-th
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The categories of this paper are: supr-con
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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
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The categories of this paper are: quant-ph
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The categories of this paper are: eess
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The categories of this paper are: funct-an
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The categories of this paper are: acc-phys
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The categories of this paper are: solv-int