Quiescent Light Curve of Accreting Neutron Star MAXI J0556-332

Liu, Helei; Matsuo, Y.; Hashimoto, Minoru; Noda, Tsuneo; Fujimoto, Masayuki Y.

doi:10.7566/jpsj.86.123901

Cited by 4 publications

(2 citation statements)

References 29 publications

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“…where s is specific entropy and µ i and N i are the chemical potential and the number per unit mass of the i-th elements, respectively. The latter term ε h g indicates the compressional heating due to the accretion, which significantly contributes in the heat source in some cases (e.g., Liu et al 2017).…”

Section: The Basic Equationsmentioning

confidence: 99%

Effects of Nuclear Equation of State on Type-I X-ray Bursts: Interpretation of the X-ray Bursts from GS 1826-24

Dohi,

Nishimura,

Hashimoto

et al. 2021

Preprint

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Type I X-ray bursts are thermonuclear explosions on the neutron star (NS) surface by mass accretion from a companion star. Observation of X-ray bursts provides valuable information on X-ray binary systems, e.g., binary parameters, the chemical composition of accreted matter, and the nuclear equation of state (EOS) of NSs. There have been several theoretical studies to constrain the physics of X-ray bursters. However, they were mainly focused on the burning layers above the NS surface. The effects of the EOS and the heating and cooling processes inside the NS are still unknown. In this study, we calculated a series of X-ray bursts using a general relativistic stellar-evolution code with several NS EOSs. We compared the X-ray burst models with the burst parameters of a clocked burster associated with GS 1826-24. We found 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 the neutrino cooling suppress the efficiency of nuclear ignition. We also constrained the EOS and mass of GS 1826-24, i.e., stiffer EOSs, corresponding to larger NS radii, are unpreffered 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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Section: The Basic Equationsmentioning

confidence: 99%

Effects of Nuclear Equation of State on Type-I X-ray Bursts: Interpretation of the X-ray Bursts from GS 1826-24

Dohi,

Nishimura,

Hashimoto

et al. 2021

Preprint

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show abstract

“…We note that other nuclear reactions may be taking place which are currently unaccounted for. Liu et al (2017) calculate cooling curves for MAXI J0556-332 without shallow heating but including the full beta-decay limited hot CNO cycle and while assuming a decaying accretion rate during quiescence. In their calculation, nuclear burning does not occur diffusively but follows a fixed burning rate for the hot CNO cycle (independent of the amount of hydrogen available and the density) in the region of the envelope where T > 10 9 K and changes in abundances are not taken into account.…”

Section: Maxi J0556-332mentioning

confidence: 99%

The effect of diffusive nuclear burning in neutron star envelopes on cooling in accreting systems

Wijngaarden

Chang

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Valuable information about the neutron star interior can be obtained by comparing observations of thermal radiation from a cooling neutron star crust with theoretical models. Nuclear burning of lighter elements that diffuse to deeper layers of the envelope can alter the relation between surface and interior temperatures and can change the chemical composition over time. We calculate new temperature relations and consider two effects of diffusive nuclear burning (DNB) for H-C envelopes. First, we consider the effect of a changing envelope composition and find that hydrogen is consumed on short timescales and our temperature evolution simulations correspond to those of a hydrogen-poor envelope within ∼100 days. The transition from a hydrogen-rich to a hydrogen-poor envelope is potentially observable in accreting NS systems as an additional initial decline in surface temperature at early times after the outburst. Second, we find that DNB can produce a non-negligible heat flux, such that the total luminosity can be dominated by DNB in the envelope rather than heat from the deep interior. However, without continual accretion, heating by DNB in H-C envelopes is only relevant for <1-80 days after the end of an accretion outburst, as the amount of light elements is rapidly depleted. Comparison to crust cooling data shows that DNB does not remove the need for an additional shallow heating source. We conclude that solving the time-dependent equations of the burning region in the envelope selfconsistently in thermal evolution models instead of using static temperature relations would be valuable in future cooling studies.

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Thermal state of transiently accreting neutron stars with additional heating beyond deep crustal heating

Liu

Hashimoto

Matsuo³

et al. 2020

Progress of Theoretical and Experimental Physics

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As some neutron star transients require an additional unknown heat source (referred to as “shallow heating”) to explain their high temperatures at the beginning of quiescence, we investigate the effect of shallow heating as well as compressional heating on the thermal state of transiently accreting neutron stars with the use of evolutionary calculations in the present work. Through comparing our theoretical predictions of the equilibrium redshifted luminosities $(L_{\gamma}^{\infty})$ produced by both deep crustal heating and shallow heating/compressional heating for different time-averaged mass-accretion rates $\langle\dot{M}\rangle$ with 35 updated observations of soft X-ray transients, the results show that both shallow heating and compressional heating make significant contributions to the equilibrium redshifted luminosity. The hotter sources (XTE J1701, MAXI J0556, EXO 0748, Aql X-1 etc.) with higher accretion rates are more likely to be explained with the effect of shallow heating or compressional heating. In addition, for a proper shallow heat $q_\mathrm{sh}$ and mass-accretion rate $\dot{M}$, the effect of shallow heating could be simulated by compressional heating.

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Quiescent Light Curve of Accreting Neutron Star MAXI J0556-332

Cited by 4 publications

References 29 publications

Effects of Nuclear Equation of State on Type-I X-ray Bursts: Interpretation of the X-ray Bursts from GS 1826-24

Effects of Nuclear Equation of State on Type-I X-ray Bursts: Interpretation of the X-ray Bursts from GS 1826-24

The effect of diffusive nuclear burning in neutron star envelopes on cooling in accreting systems

Thermal state of transiently accreting neutron stars with additional heating beyond deep crustal heating

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