2005 Fiscal Year Final Research Report Summary
Hyperon Mixing in Supernova Matter and Neutron Stars at Birth
| Project/Area Number |
15540244
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | Iwate University |
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Principal Investigator |
NISHIZAKI Shigeru Iwate University, Faculty of Humanities & Social Sciences, Professor, 人文社会科学部, 教授 (60198455)
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| Co-Investigator(Kenkyū-buntansha) |
TAKATSUKA Tatsuyuki Iwate University, Faculty of Humanities & Social Sciences, Professor, 人文社会科学部, 教授 (50043427)
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| Project Period (FY) |
2003 – 2005
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| Keywords | Theoretical Nuclear Physics / Supernova Matter / Hyperon / Equations of Motion / Neutron Star |
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| Research Abstract |
Hot and dense matter in the interior of neutron stars just after the supernova explosion will has almost constant and large entropy due to the neutrino trapping. We studied the mixing of constituent particles in this supenova matter and revealed its characteristics as follows.
(1)The mixing ratio of electrons becomes large due to the lepton number conservation and its magnitude does not depend on the density so much and keeps almost constant.
(2)The large electron fraction results in the large proton mixing because of the charge neutrality.
(3)The mixing of Σ^- in the high-density region is largely reduced by the lepton number conservation.
By using the equation of motion (EOS) for this supernova matter, we constructed the neutron star model. Its characteristics are as follows.
(1)The maximum mass of neutron staras at birth is 1.84 times solar mass and is larger than that resulting from cold neutron star matter (1.82 times solar mass). This is due to the hardening of EOS.
(2)Since the baryon number is conserved in the cooling stage of hot neutron stars at birth, the maximum mass of cooled neutron star is smaller than that estimated by EOS of neutron star matter and decreases to (1.75-1.79) times solar mass.
(3)The density distribution in the interior of neutron stars becomes flatter and decreases rapidly at the surface as they cool. This tendency is contrasted with the result from EOS without hyperons. In this case, the central density increases and the radius decreases as neutron stars become cooler. The fraction of protonts in the interior of neutron stars decreases and that of Σ^- increases as they cools.
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Research Products
(6 results)
