期刊
ASTROPHYSICAL JOURNAL
卷 923, 期 1, 页码 -出版社
IOP Publishing Ltd
DOI: 10.3847/1538-4357/ac2821
关键词
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资金
- JSPS KAKENHI [19H00693, 20H05648, 21H01087]
- RIKEN pioneering project Evolution of Matter in the Universe (r-EMU)
- Incentive Research Project (IRP) at RIKEN
- Grants-in-Aid for Scientific Research [20H05648, 21H01087] Funding Source: KAKEN
Studying the microphysics inside neutron stars, a study found a monotonic correlation between the neutron star radius and the light-curve profile of X-ray bursts, with a larger radius showing higher recurrence time and peak luminosity. Neutrino cooling suppresses the efficiency of nuclear ignition, making the dependence of light curves on neutron star mass more complicated. The equation of state and the cooling and heating of neutron stars are crucial for discussing the theoretical and observational properties of X-ray bursts.
Type I X-ray bursts are thermonuclear explosions on the neutron star (NS) surface caused by mass accretion from a companion star. Observations of X-ray bursts provide valuable information on X-ray binary systems, e.g., binary parameters, the chemical composition of accreted matter, and the nuclear equation of state (EOS). There have been several theoretical studies to constrain the physics of X-ray bursters. However, they have mainly focused on the burning layers above the solid crust of the NS, which brings up issues of the treatment of NS gravitational and internal energy. In this study, focusing on the microphysics inside NSs, we calculate a series of X-ray bursts using a general-relativistic stellar-evolution code with several NS EOSs. We compare the X-ray-burst models with the burst parameters of a clocked burster associated with GS 1826-24. We find a monotonic correlation between the NS radius and the light-curve profile. A larger radius shows a higher recurrence time and a large peak luminosity. In contrast, the dependence of light curves on the NS mass becomes more complicated, where neutrino cooling suppresses the efficiency of nuclear ignition. We also constrain the EOS and mass of GS 1826-24, i.e., stiffer EOSs, corresponding to larger NS radii, are not preferred due to a too-high peak luminosity. The EOS and the cooling and heating of NSs are important to discuss the theoretical and observational properties of X-ray bursts.
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