Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of a Candidate Black Hole - Giant Star Binary System in the
  Galactic Field   We report the discovery of the first likely black hole in a non-interacting
binary system with a field red giant. By combining radial velocity measurements
from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) with
photometric variability data from the All-Sky Automated Survey for Supernovae
(ASAS-SN), we identified the bright rapidly-rotating giant 2MASS
J05215658+4359220 as a binary system with a massive unseen companion.
Subsequent radial velocity measurements reveal a system with an orbital period
of 83 days and near-zero eccentricity. The photometric variability period of
the giant is consistent with the orbital period, indicative of star spots and
tidal synchronization. Constraints on the giant's mass and radius from its
luminosity, surface gravity, and temperature imply an unseen companion with
mass of $3.3^{+2.8}_{-0.7}$ M$_\odot$, indicating a low-mass black hole or an
exceedingly massive neutron star. Measurement of the astrometric binary motion
by {\it Gaia} will further characterize the system. This discovery demonstrates
the potential of massive spectroscopic surveys like APOGEE and all-sky,
high-cadence photometric surveys like ASAS-SN to revolutionize our
understanding of the compact object mass function, and to test theories of
binary star evolution and the supernova mechanism.

31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math