Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Chemical Distribution in a Subluminous Type Ia Supernova: HST Images
  of the SN 1885 Remnant   We present HST images of the remnant of SN 1885 seen in absorption against
M31's bulge via resonance lines of Ca I, Ca II, Fe I, and Fe II. Viewed in CaII
H & K line absorption, the remnant appears as a nearly black circular spot with
an outermost angular radius of 0.40" +/- 0.025" implying r = 1.52 pc and a 120
yr average expansion velocity of 12400 +/-1400 km/s. The strongest Ca II
absorption is organized in a broken ring structure with a radius of 0.20"
(=6000 km/s) with several apparent absorption `clumps' of an angular size near
the pixel scale of 0.05" (= 1500 km/s). The detection of Ca II clumps is the
first direct evidence for some instabilities and the existence of a
deflagration phase in SNe Ia or, alternatively, mixing induced by radioactive
decay of 56^Ni over time scales of seconds or days. However, the degree of
mixing allowed by the observed images is much smaller than current 3D
calculations for Rayleigh-Taylor dominated deflagration fronts. The images also
require a central region of no or little Ca but iron group elements indicative
of burning under sufficiently high densities for electron capture taking place,
i.e., burning prior to a significant pre-expansion of the WD.

0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
2
The categories of this paper are: math