Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chandra Observations of Candidate Sub-Parsec Binary Supermassive Black
  Holes   We present analysis of Chandra X-ray observations of seven quasars that were
identified as candidate sub-parsec binary supermassive black hole (SMBH)
systems in the Catalina Real-Time Transient Survey (CRTS) based on apparent
periodicity in their optical light curves. Simulations predict close-separation
accreting SMBH binaries will have different X-ray spectra than single accreting
SMBHs, including harder or softer X-ray spectra, ripple-like profiles in the Fe
K-$\alpha$ line, and distinct peaks in the spectrum due to the separation of
the accretion disk into a circumbinary disk and mini-disks around each SMBH. We
obtained Chandra observations to test these models and assess whether these
quasars could contain binary SMBHs. We instead find that the quasar spectra are
all well fit by simple absorbed power law models, with the rest frame 2-10 keV
photon indices, $\Gamma$, and the X-ray-to-optical power slopes, $\alpha_{\rm
OX}$, indistinguishable from the larger quasar population. This may indicate
that these seven quasars are not truly sub-parsec binary SMBH systems, or it
may simply reflect that our sample size was too small to robustly detect any
differences. Alternatively, the X-ray spectral changes might only be evident at
higher energies than probed by Chandra. Given the available models and current
data, no firm conclusions are drawn. These observations will help motivate and
direct further work on theoretical models of binary SMBH systems, such as
modeling systems with thinner accretion disks and larger binary separations.

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The categories of this paper are: dg-ga
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The categories of this paper are: hep-th
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The categories of this paper are: ao-sci
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The categories of this paper are: quant-ph
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The categories of this paper are: math
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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: alg-geom
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The categories of this paper are: q-alg
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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: q-fin
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The categories of this paper are: econ
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph