Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photon-axion mixing in thermal emission of isolated neutron stars   Thermally emitting neutron stars represent a promising environment for
probing the properties of axion-like particles. Due to the strong magnetic
fields of these sources, surface photons may partially convert into such
particles in the large magnetospheric region surrounding the stars, which will
result in distinctive signatures in their spectra. However, the interaction
depends on the polarization state of the radiation and is rather weak due to
the low experimentally allowed values of the coupling constant $g_{\gamma a}$.
In this work, we compute the degree of photon-axion transition in the case of
100% O-mode polarization and spectral energy distribution of an isotropic
blackbody with uniform surface temperature. The stellar magnetic field is
assumed to be dipolar. We show that with the maximum effect reached for the
magnetic fields $\sim10^{13}$ - $10^{14}$ G (typical for X-ray dim isolated
neutron stars) and $g_{\gamma a} = 2 \times 10^{-11}$ GeV$^{-1}$, the optical
flux is reduced by 30 - 40%, while the high-energy part of the spectrum is not
affected. The low-energy decrease exceeds 5% at $g_{\gamma a} \geq 2 \times
10^{-12}$ GeV$^{-1}$ and $m_a \leq 2\times 10^{-6}$ eV, which is below the
present experimental and astrophysical limits on axion parameters. To obtain
the actual observational constraints, rigorous treatment of the radiative
surface layers is required.

27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
1
The categories of this paper are: cs