Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Reddening Towards Cassiopeia A's Supernova: Constraining the 56Ni
  Yield   We present new reddening measurements towards the young supernova remnant
Cassiopeia A, using two techniques not previously applied to this object. Our
observations of the near-infrared [Fe II] 1.257 micron and 1.644 micron lines
show the extinction to be highly variable across the remnant, increasing
towards the west and the south, consistent with previous radio and X-ray
observations. While the absolute value of AV as determined by the [Fe II] lines
is uncertain due to conflicting calculations and observations of their
intrinsic flux ratio, parts of the remnant without previous optical
measurements show comparatively higher reddening. We find AV = 6.2 +/- 0.6 from
the broadband shape of the infrared synchrotron emission of a knot within 13"
of the expansion center. Given this reddening, the apparent faintness of the
nascent supernova, and iron mass constraints from X-ray observations, we
estimate an ejected mass of 56Ni of 0.058 - 0.16 MSun. Taken with gamma-ray
observations of the 44Ti decay chain, this nickel mass is broadly consistent
with the solar 44Ca/56Fe ratio.

37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
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The categories of this paper are: quant-ph