Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray/UV variability and the origin of soft X-ray excess emission from
  II Zw 177   We study X-ray and UV emission from the narrow-line Seyfert 1 galaxy
II~Zw~177 using a $137\ks$ long and another $13\ks$ short \xmm{} observation
performed in 2012 and 2001, respectively. Both observations show soft X-ray
excess emission contributing $76.9\pm4.9\%$ in 2012 and $58.8\pm10.2\%$ in 2001
in the $0.3-2\kev$ band. We find that both blurred reflection from an ionized
disc and Comptonized disc emission describe the observed soft excess well.
Time-resolved spectroscopy on scales of $\sim20\ks$ reveals strong correlation
between the soft excess and the powerlaw components. The fractional variability
amplitude $F_{var}$ derived from EPIC-pn lightcurves at different energy bands
is nearly constant ($F_{var} \sim20\%$). This is in contrast to other AGNs
where the lack of short term variation in soft X-ray excess emission has been
attributed to intense light bending in the framework of the "lamppost" model.
Thus, the variations in powerlaw emission are most likely intrinsic to corona
rather than just due to the changes of height of compact corona. The variable
UV emission ($F_{var} \sim 1\%$) is uncorrelated to any of the X-ray components
on short timescales suggesting that the UV emission is not dominated by the
reprocessed emission. The gradual observed decline in the UV emission in 2012
may be related to the secular decline due to the changes in the accretion rate.
In this case, the short term X-ray variability is not due to the changes in the
seed photons but intrinsic to the hot corona.

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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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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: ao-sci
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: math