Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Constraints on Circumstellar Material Around the Type Ia Supernova
  2007af   Patat et al. recently inferred the existence of circumstellar material around
a normal Type Ia supernova (SN) for the first time, finding time-variable Na I
D absorption lines in the spectrum of SN 2006X. We present high-resolution
spectroscopy of the bright SN Ia 2007af at three epochs and search for
variability in any of the Na D absorption components. Over the time range from
4 days before to 24 days after maximum light, we find that the host-galaxy Na D
lines appear to be of interstellar rather than circumstellar origin and do not
vary down to the level of 18 mA (column density of 2 x 10^11 cm^-2). We limit
any circumstellar absorption lines to be weaker than ~10 mA (6 x 10^10 cm^-2).
For the case of material distributed in spherically symmetric shells of radius
~10^16 cm surrounding the progenitor system, we place an upper limit on the
shell mass of ~(3 x 10^-8)/X Msun, where X is the Na ionization fraction. We
also show that SN 2007af is a photometrically and spectroscopically normal SN
Ia. Assuming that the variable Na D lines in SN 2006X came from circumstellar
matter, we therefore conclude that either there is a preferred geometry for the
detection of variable absorption components in Type Ia supernovae, or SN 2007af
and SN 2006X had different types of progenitor systems.

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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: adap-org
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: hep-lat
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: econ
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The categories of this paper are: cond-mat
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The categories of this paper are: cs
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex