Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: New X-ray bound on density of primordial black holes   We set a new upper limit on the abundance of primordial black holes (PBH)
based on existing X-ray data. PBH interactions with interstellar medium should
result in significant fluxes of X-ray photons, which would contribute to the
observed number density of compact X-ray objects in galaxies. The data
constrain PBH number density in the mass range from a few $M_\odot$ to $2\times
10^7 M_\odot$. PBH density needed to account for the origin of black holes
detected by LIGO is marginally allowed.

17
The categories of this paper are: q-fin
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The categories of this paper are: eess
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph