Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Atmospheric reflection during an anomalous low-state of Hercules X-1   We present RXTE observations of the eclipsing X-ray binary Hercules X-1
conducted during an anomalous low state. Data reduction reveals a light curve
over 2.7 orbital cycles remarkably similar to optical and UV light curves which
are dominated by the companion star. Count rates are modulated close to the
orbital period, attaining a maximum when the inner face of the companion star,
irradiated by X-rays from the compact source, is most-visible. Cold reflection
provides an acceptable fit to the energy spectrum. Employing binary geometry to
scale the model and assuming companion star reflection, we are able to
reconstruct the incident X-rays which are removed from our direct line-of-sight
(presumably by the accretion disk). We find the flux of the hidden source to be
identical to the observed flux of Her X-1 at the peak of its main-high state.
Consequently, Her X-1 is emitting a reflected spectrum, largely uncontaminated
by direct X-rays in the anomalous low-state. The spectral energy distribution,
period, amplitude and phasing of the modulation are all consistent with a
companion star origin. Since this source occurs in a well-understood binary
environment, it provides an excellent case study for more sensitive experiments
in the future.

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The categories of this paper are: math-ph
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The categories of this paper are: cs
9
The categories of this paper are: nlin
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The categories of this paper are: acc-phys
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The categories of this paper are: atom-ph
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The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
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The categories of this paper are: math
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th