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中性子星観測から迫る原子核飽和パラメータの制限

Publicly Offered Research

Project AreaNuclear matter in neutron stars investigated by experiments and astronomical observations
Project/Area Number 15H00843
Research Category

Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

Allocation TypeSingle-year Grants
Review Section Science and Engineering
Research InstitutionNational Astronomical Observatory of Japan

Principal Investigator

祖谷 元  国立天文台, 理論研究部, 特任助教 (70386720)

Project Period (FY) 2015-04-01 – 2017-03-31
Project Status Completed (Fiscal Year 2016)
Budget Amount *help
¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
Fiscal Year 2016: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2015: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Keywords中性子星 / 状態方程式 / 宇宙物理
Outline of Annual Research Achievements

原子核の飽和性のため、地上原子核実験で得られる情報は基本的に飽和密度付近のものに限られる。また、標準核密度を優に超える中性子星物質に対する状態方程式は、理論的にはいくつも提唱されているが未だ決まっておらず、中性子星の詳細な構造も不確定である。そのため、中性子星の観測はこのような高密度領域における物理を探る上で非常に有益である。
地上実験では原子核飽和パラメータに制限をある程度与えることができるため、その範囲で低密度側における状態方程式を記述することができる。実際、中心密度が飽和密度の2倍程度までであれば、中性子星の半径や質量をうまく飽和パラメータで記述できることがわかっている。一方、高密度側の状態方程式は実験的な制限はないが、音速という物理量が一つの重要なパラメータとなる。理論的には、音速は光速を超えないという制限がある一方、安定性からは音速は非負である必要がある。また、原子核物理に於いて高密度における音速は光速を3の平方根で割ったものを越えないという推論がある。そこで、低密度側を原子核飽和パラメータで、高密度側を最大音速でパラメータ化した状態方程式を用いて中性子星の構造を解析したところ、中性子星の最大質量を原子核飽和パラメータと高密度領域の最大音速でうまく表すことに成功した。現在、観測されている中性子星の最大質量として、(2.74±0.21)太陽質量が正しいとすると、現在の原子核飽和パラメータの制限に於いては高密度領域の最大音速は少なくとも光速の75%以上でなければならないことになる。今後、より重い中性子星の観測を通して、高密度領域における最大音速により厳しい制限を与えることができ、その結果、高密度における状態方程式にも制限を与えることにつながる。

Research Progress Status

28年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

28年度が最終年度であるため、記入しない。

Report

(2 results)
  • 2016 Annual Research Report
  • 2015 Annual Research Report
  • Research Products

    (27 results)

All 2017 2016 2015 Other

All Int'l Joint Research (1 results) Journal Article (10 results) (of which Int'l Joint Research: 2 results,  Peer Reviewed: 10 results,  Acknowledgement Compliant: 10 results) Presentation (16 results) (of which Int'l Joint Research: 13 results,  Invited: 5 results)

  • [Int'l Joint Research] University of Tuebingen(ドイツ)

    • Related Report
      2016 Annual Research Report
  • [Journal Article] Probing nuclear bubble structure via neutron star asteroseismology2017

    • Author(s)
      Hajime Sotani, Kei Iida, Kazuhiro Oyamatsu
    • Journal Title

      Monthly Notices of the Royal Astronomical Society

      Volume: 464 Issue: 3 Pages: 3101-3107

    • DOI

      10.1093/mnras/stw2575

    • Related Report
      2016 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Journal Article] Effect of nuclear saturation parameters on a possible maximum mass of neutron stars2017

    • Author(s)
      Hajime Sotani
    • Journal Title

      Physical Review C

      Volume: 95 Issue: 2

    • DOI

      10.1103/physrevc.95.025802

    • Related Report
      2016 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Journal Article] Quark matter with strong magnetic field and possibility of the third family of compact stars2017

    • Author(s)
      Hajime Sotani, Toshitaka Tatsumi
    • Journal Title

      Monthly Notices of the Royal Astronomical Society

      Volume: 467 Pages: 1249-1258

    • DOI

      10.1093/mnras/stx219

    • Related Report
      2016 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Journal Article] Maximum mass limit of neutron stars in scalar-tensor gravity2017

    • Author(s)
      Hajime Sotani, Kostas D. Kokkotas
    • Journal Title

      Physical Review D

      Volume: 95 Issue: 4

    • DOI

      10.1103/physrevd.95.044032

    • Related Report
      2016 Annual Research Report
    • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
  • [Journal Article] Low-mass neutron stars: universal relations, the nuclear symmetry energy and gravitational radiation2016

    • Author(s)
      Hector O. Silva, Hajime Sotani, Emanuele Berti
    • Journal Title

      Monthly Notices of the Royal Astronomical Society

      Volume: 459 Issue: 4 Pages: 4378-4388

    • DOI

      10.1093/mnras/stw969

    • Related Report
      2016 Annual Research Report
    • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
  • [Journal Article] Gravitational wave asteroseismology with protoneutron stars2016

    • Author(s)
      Hajime Sotani, Tomoya Takiwaki
    • Journal Title

      Physical Review D

      Volume: 94 Issue: 4

    • DOI

      10.1103/physrevd.94.044043

    • Related Report
      2016 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Journal Article] Possible identifications of newly observed magnetar quasi-periodic oscillations as crustal shear modes2016

    • Author(s)
      Hajime Sotani, Kei Iida, Kazuhiro Oyamatsu
    • Journal Title

      New Astronomy

      Volume: 43 Pages: 80-86

    • DOI

      10.1016/j.newast.2015.08.003

    • Related Report
      2015 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Journal Article] Empirical formula of crustal torsional oscillations2016

    • Author(s)
      Hajime Sotani
    • Journal Title

      Physical Review D

      Volume: 93 Issue: 4

    • DOI

      10.1103/physrevd.93.044059

    • Related Report
      2015 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Journal Article] Strong gravitational lensing by an electrically charged black hole in Eddington-inspired Born-Infeld gravity2015

    • Author(s)
      H. Sotani and U. Miyamoto
    • Journal Title

      Physical Review D

      Volume: 92 Issue: 4 Pages: 044052-044052

    • DOI

      10.1103/physrevd.92.044052

    • Related Report
      2015 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Journal Article] Torsional oscillations of neutron stars with highly tangled magnetic fields2015

    • Author(s)
      Hajime Sotani
    • Journal Title

      Physical Review D

      Volume: 92 Issue: 10

    • DOI

      10.1103/physrevd.92.104024

    • Related Report
      2015 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Presentation] 巨大フレア現象と中性子星における空孔相の痕跡2017

    • Author(s)
      祖谷元,飯田圭,親松和浩
    • Organizer
      日本物理学会
    • Place of Presentation
      大阪大学(大阪府豊中市)
    • Year and Date
      2017-03-17
    • Related Report
      2016 Annual Research Report
  • [Presentation] Protoneutron star properties via gravitational wave asteroseismology2017

    • Author(s)
      Hajime Sotani
    • Organizer
      Quarks and Compact Stars 2017 (QCS2017)
    • Place of Presentation
      京都大学(京都府京都市)
    • Year and Date
      2017-02-20
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Gravitational waves from protoneutron stars2017

    • Author(s)
      Hajime Sotani
    • Organizer
      Testing Gravity 2017
    • Place of Presentation
      Vancouver, Canada
    • Year and Date
      2017-01-26
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Probing the nuclear symmetry energy via neutron star asteroseismology2016

    • Author(s)
      Hajime Sotani
    • Organizer
      International Symposium on Neutron Star Matter (NSMAT2016)
    • Place of Presentation
      東北大学(宮城県仙台市)
    • Year and Date
      2016-11-23
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Gravitational wave asteroseismology in protoneutron stars2016

    • Author(s)
      Hajime Sotani
    • Organizer
      NEB 17 - Recent Developments in Gravity
    • Place of Presentation
      Mykonos, Greece
    • Year and Date
      2016-09-19
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Scalar-gravitational waves from relativistic stars in scalar-tensor gravity2016

    • Author(s)
      Hajime Sotani
    • Organizer
      Gravitational Waves from modified gravity theories
    • Place of Presentation
      Athens, Greece
    • Year and Date
      2016-09-15
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research / Invited
  • [Presentation] Gravitational waves of core-collapse supernova at post-bounce phase2016

    • Author(s)
      Hajime Sotani
    • Organizer
      21st International Conference on General Relativity and Gravitation (GR21)
    • Place of Presentation
      New York, USA
    • Year and Date
      2016-07-13
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Crustal torsional oscillations and nuclear symmetry energy2016

    • Author(s)
      Hajime Sotani
    • Organizer
      Nuclei in the Cosmos XIV (NIC2016)
    • Place of Presentation
      朱鷺メッセ(新潟県新潟市)
    • Year and Date
      2016-06-22
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Nuclear symmetry energy and crustal torsional oscillations in neutron stars2016

    • Author(s)
      Hajime Sotani
    • Organizer
      6th International Symposium on Nuclear Symmetry Energy (NuSYM16)
    • Place of Presentation
      Beijing, China
    • Year and Date
      2016-06-17
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research / Invited
  • [Presentation] 高密度星の系列における第三の分枝の可能性2016

    • Author(s)
      祖谷元,巽敏隆
    • Organizer
      日本物理学会
    • Place of Presentation
      東北学院大学(宮城県仙台市)
    • Year and Date
      2016-03-19
    • Related Report
      2015 Annual Research Report
  • [Presentation] 中性子星クラスト振動と電子遮蔽効果2015

    • Author(s)
      祖谷元,飯田圭,親松和浩
    • Organizer
      日本物理学会
    • Place of Presentation
      大阪市立大学(大阪府大阪市)
    • Year and Date
      2015-09-28
    • Related Report
      2015 Annual Research Report
  • [Presentation] Identifications of Quasi-Periodic Oscillations Observed in Soft-Gamma Repeaters with Crustal Torsional Oscillations2015

    • Author(s)
      Hajime Sotani
    • Organizer
      Fourteenth Marcel Grossmann Meeting (MG14)
    • Place of Presentation
      Rome, Italy
    • Year and Date
      2015-07-13
    • Related Report
      2015 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Prospect for Observational Discriminant of the Gravitational Theories2015

    • Author(s)
      Hajime Sotani
    • Organizer
      Fourteenth Marcel Grossmann Meeting (MG14)
    • Place of Presentation
      Rome, Italy
    • Year and Date
      2015-07-13
    • Related Report
      2015 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Nuclear equation of state and crustal torsional oscillations2015

    • Author(s)
      Hajime Sotani
    • Organizer
      COMPACT STARS AND BLACK HOLES
    • Place of Presentation
      Tuebingen, Germany
    • Year and Date
      2015-07-08
    • Related Report
      2015 Annual Research Report
    • Int'l Joint Research / Invited
  • [Presentation] Mass formula for low-mass neutron stars and its application2015

    • Author(s)
      Hajime Sotani
    • Organizer
      5th International Symposium on Nuclear Symmetry Energy (NuSYM15)
    • Place of Presentation
      Krakow, Poland
    • Year and Date
      2015-06-30
    • Related Report
      2015 Annual Research Report
    • Int'l Joint Research / Invited
  • [Presentation] Neutron star oscillations and equation of state2015

    • Author(s)
      Hajime Sotani
    • Organizer
      International Symposium on "Physics and Astronomy of Neutron Stars and Supernovae"
    • Place of Presentation
      NAOJ, Mitaka, Tokyo, Japan
    • Year and Date
      2015-06-22
    • Related Report
      2015 Annual Research Report
    • Int'l Joint Research / Invited

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Published: 2015-04-16   Modified: 2018-03-28  

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