Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First optical identification of a suprsoft X-ray source in M31   We propose the first association of an optical counterpart with a luminous
supersoft X-ray source in M31, RX J0044.0+4118, observed with ROSAT in July
1991. The PSPC position is at 1.6" angular distance from a candidate nova in
outburst in September of 1990. This is interesting because the incidence of
classical novae among supersoft X-ray sources is an open question. The proposed
optical counterpart was measured at R~17.7 in September of 1990, and it had
faded to R>19.2 when it was observed again after 70 days.
  The light curve was too sparsely monitored for definite conclusions on the
speed class of the nova. No other variable objects with V<23.5 were found in
the ROSAT spatial error box. We evaluate that the probability that a classical
or recurrent nova was in outburst in the ROSAT error box in the few years
preceding the observation is very small, so the proposed identification is
meaningful. We also show evidence that the associated supersoft X-ray source
turned off in the third year after the outburst.

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The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
17
The categories of this paper are: q-fin