Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The need for a second black hole at the Galactic center   Deep infra-red observations and long-term monitoring programs have provided
dynamical evidence for a supermassive black hole of mass 3.e6 solar masses
associated with the radio source Sagitarrius A* at the center of our Galaxy.
The brightest stars orbiting within 0.1 parsecs of the black hole appear to be
young, massive main sequence stars, n spite of an environment near the black
hole that is hostile to star formation. We discuss mechanisms by which stars
born outside the central parsec can sink towards the black hole and conclude
that the drag coming from plausible stellar populations does not operate on the
short timescales required by the stellar ages. We propose that these stars were
dragged in by a second black hole of mass of 1.e3-1.e4 solar masses, which
would be classified as an intermediate-mass black hole. We discuss the
implications for the stellar populations and the kinematics in the Galactic
center. Finally we note that continued astrometric monitoring of the central
radio source offers the prospect for a direct detection of such objects.

22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys