Evidence of Nuclear Urca Process in the Ocean of Neutron-Star Superburst MAXI J1752$-$457
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arXiv
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| Autori principali: | , , , , |
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| Natura: | Preprint |
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2026
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| _version_ | 1866914342287441920 |
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| author | Huang, Hao Dohi, Akira Aoyama, Amira Takeda, Tomoshi Nishimura, Nobuya |
| author_facet | Huang, Hao Dohi, Akira Aoyama, Amira Takeda, Tomoshi Nishimura, Nobuya |
| contents | We propose that the rapid cooling of the neutron star following its X-ray superburst in MAXI J1752$-$457 over a period of 4 days, observed by two Japanese satellites, MAXI and NinjaSat, is due to enhanced neutrino emission from cycles of electron capture and $β^{-}$ decay involving odd-$A$ nuclei (or Urca pairs) in the ocean. Hence, this work provides the first indication of the possible existence of such a ``nuclear Urca process". The observation of MAXI J1752$-$457 implies a hot ignition layer with a maximum temperature of $\sim4~{\rm GK}$, located near the Urca shell in the ocean, such that the nuclear Urca process becomes dominant for up to $\sim2$ days after the superburst. This behavior is distinct from that of normal Type-I X-ray bursts, which are triggered by hydrogen or helium burning in much shallower layers than those of superbursts. Our findings enable probing of superburst ashes through Urca pairs via long-term monitoring of crust cooling on day-long timescales. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_19018 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Evidence of Nuclear Urca Process in the Ocean of Neutron-Star Superburst MAXI J1752$-$457 Huang, Hao Dohi, Akira Aoyama, Amira Takeda, Tomoshi Nishimura, Nobuya High Energy Astrophysical Phenomena Nuclear Experiment Nuclear Theory We propose that the rapid cooling of the neutron star following its X-ray superburst in MAXI J1752$-$457 over a period of 4 days, observed by two Japanese satellites, MAXI and NinjaSat, is due to enhanced neutrino emission from cycles of electron capture and $β^{-}$ decay involving odd-$A$ nuclei (or Urca pairs) in the ocean. Hence, this work provides the first indication of the possible existence of such a ``nuclear Urca process". The observation of MAXI J1752$-$457 implies a hot ignition layer with a maximum temperature of $\sim4~{\rm GK}$, located near the Urca shell in the ocean, such that the nuclear Urca process becomes dominant for up to $\sim2$ days after the superburst. This behavior is distinct from that of normal Type-I X-ray bursts, which are triggered by hydrogen or helium burning in much shallower layers than those of superbursts. Our findings enable probing of superburst ashes through Urca pairs via long-term monitoring of crust cooling on day-long timescales. |
| title | Evidence of Nuclear Urca Process in the Ocean of Neutron-Star Superburst MAXI J1752$-$457 |
| topic | High Energy Astrophysical Phenomena Nuclear Experiment Nuclear Theory |
| url | https://arxiv.org/abs/2602.19018 |