Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Possible Detection of M31* with Chandra   Two independent sets of Chandra and HST images of the nuclear region of M31
allow registration of X-ray and optical images to 0.1''. This registration
shows that none of the bright (10^{37} erg/s) X-ray sources near the nucleus is
coincident with the central super-massive black hole, M31*. A 50ks Chandra HRC
image shows 2.5 sigma evidence for a faint (3 x 10^{35} erg/s), apparently
resolved source which is consistent with the position of the M31*. The Bondi
radius of M31* is 0.9'', making it one of the few super-massive black holes
with a resolvable accretion flow. This large radius and the previous detections
of diffuse, X-ray emitting gas in the nuclear region make M31* one of the most
secure cases for a radiatively inefficient accretion flow and place some of the
most severe constraints on the radiative processes in such a flow.

24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys