Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Near-infrared counterparts of ultraluminous X-ray sources   In this paper we present the results of the first systematic search for
counterparts to nearby ultraluminous X-ray sources (ULXs) in the near-infrared
(NIR). We observed 62 ULXs in 37 galaxies within 10 Mpc and discovered 17
candidate NIR counterparts. The detection of 17 out of 62 ULX candidates points
to intrinsic differences between systems that show and those that do not show
infrared emission. For six counterparts we conclude from the absolute
magnitudes and - - in some cases - additional information such as morphology
and previously reported photometric or spectroscopic observations, that they
are likely background active galactic nuclei or ULXs residing in star clusters.
Eleven counterparts have absolute magnitudes consistent with them being single
red supergiant stars. Alternatively, these systems may have larger accretion
discs that emit more NIR light than the systems that we do not detect. Other
scenarios such as emission from a surrounding nebula or from a compact radio
jet are also possible, although for Holmberg II X-1 the NIR luminosity far
exceeds the expected jet contribution. The eleven possible red supergiant
counterparts are excellent candidates for spectroscopic follow-up observations.
This may enable us to measure the mass function in these systems if they are
indeed red supergiant donor stars where we can observe absorption lines.

10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
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
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg