Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for a TDE origin of the radio transient Cygnus A-2   In 2015, a radio transient named Cygnus A-2 was discovered in Cygnus A with
the Very Large Array. Because of its radio brightness ($\nu F_{\nu} \approx 6
\times 10^{39}$ erg s$^{-1}$), this transient likely represents a secondary
black hole in orbit around the AGN. Using {\it Chandra} ACIS observations from
2015 to 2017, we have looked for an X-ray counterpart to Cygnus A-2. The
separation of 0.42 arcsec means that Cygnus A-2 can not be spatially resolved,
but by comparing the data with simulated \texttt{marx} data, we put an upper
limit to the 2-10 keV X-ray luminosity of Cygnus A-2 of $1 \times 10^{43}$ erg
s$^{-1}$. Using the Fundamental Plane for accreting black holes, we find that
our upper limit to the X-ray flux of Cygnus A-2 in 2015-2017 disfavours the
interpretation of Cygnus A-2 as a steadily accreting black hole. We suggest
instead that Cygnus A-2 is the radio afterglow of a tidal disruption event
(TDE), and that a peak in the 2-10 keV luminosity of the nuclear region in
2013, when it was observed by {\it Swift} and {\it NuSTAR}, is X-ray emission
from the TDE. A TDE could naturally explain the X-ray light curve of the
nuclear region, as well as the appearance of a short-lived, fast, and ionized
outflow previously detected in the 2013 {\it NuSTAR} spectrum. Both the radio
and X-ray luminosities fall in between typical luminosities for 'thermal' and
'jetted' TDE types, suggesting that Cygnus A-2 would be unlike previously seen
TDE's.

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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: gr-qc
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The categories of this paper are: q-fin
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The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: solv-int
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: nucl-ex