A1 Refereed original research article in a scientific journal
Neutrino beaming in ultraluminous X-ray pulsars as a result of gravitational lensing by neutron stars
Authors: Mushtukov, A. A.; Potekhin, A. Y.; Markozov, I. D.; Nallan, S.; Kornacka, K.; Ognev, I. S.; Kravtsov, V; Dobrynina, A. A.; Kaminker, A. D.
Publisher: OXFORD UNIV PRESS
Publishing place: OXFORD
Publication year: 2025
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 538
Issue: 4
First page : 2396
Last page: 2407
Number of pages: 12
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/staf435
Web address : https://academic.oup.com/mnras/article/538/4/2396/8082115
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/492307871
X-ray pulsars experiencing extreme mass accretion rates can produce neutrino emission in the MeV energy band. Neutrinos in these systems are emitted in close proximity to the stellar surface and subsequently undergo gravitational bending in the space curved by a neutron star. This process results in the formation of a distinct beam pattern of neutrino emission and gives rise to the phenomenon of neutrino pulsars. The energy flux of neutrinos, when averaged over the neutron star's pulsation period, can differ from the isotropic neutrino energy flux, which impacts the detectability of bright pulsars in neutrinos. We investigate the process of neutrino beam pattern formation, accounting for neutron star transparency to neutrinos and gravitational bending. Based on simulated neutrino beam patterns, we estimate the potential difference between the actual and apparent neutrino luminosity. We show that the apparent luminosity can greatly exceed the actual luminosity, albeit only in a small fraction of cases, depending on the specific equation of state and the mass of the star. For example, the amplification can exceed a factor of 10 for approximate to 0.05percent of typical neutron stars with the mass of 1.4M(circle dot). Strong amplification is less probable for neutron stars of higher mass. In the case of strange stars, a fraction of high-energy neutrinos can be absorbed, and the beam pattern, as well as the amplification of apparent neutrino luminosity, depends on neutrino energy.
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Funding information in the publication:
The work of AYP and IDM was partially supported by the Ministry of Science and Higher Education of the Russian Federation (agreement no. 075-15-2024-647).