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Study of variations of cyclotron lines in neutron stars with luminosity and pulse phase using PC cluster.

Research Project

Project/Area Number 19K03934
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeMulti-year Fund
Section一般
Review Section Basic Section 16010:Astronomy-related
Research InstitutionNagano National College of Technology

Principal Investigator

Nishimura Osamu  長野工業高等専門学校, 情報エレクトロニクス系, 教授 (10259864)

Project Period (FY) 2019-04-01 – 2023-03-31
Project Status Completed (Fiscal Year 2022)
Budget Amount *help
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2021: ¥390,000 (Direct Cost: ¥300,000、Indirect Cost: ¥90,000)
Fiscal Year 2020: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Fiscal Year 2019: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
KeywordsX線パルサー / 中性子星 / サイクロトロン線 / 磁場 / 重力レンズ効果 / サイクロトロン共鳴
Outline of Research at the Start

宇宙において最も強い磁場を持つ天体が中性子星であり,その磁場強度を直接測定できる唯一の方法が本研究テーマであるサイクロトロン吸収線(以下,吸収線)のエネルギーである.中性子星の中には伴星を伴う場合があり,伴星からガスが降り積もることでX線を放射している.この降着ガスの運動は強磁場に沿って一次元運動し,星表面近くで衝撃波発生により急激に減速されるため無視されてきた.しかし,降着円柱の壁付近では輻射圧の減少のためガス運動の減速が弱くなると考えられる.本研究では,吸収線形成はこの壁付近の領域が支配的になることに注目し,二次元で考えることで今までの一次元標準モデルで解決できなかった問題を解明する.

Outline of Final Research Achievements

I compute cyclotron absorption line in neutron stars numerically, building a model that is able to reproduce a variation of the observed energy of absorption line with luminosity. In Vela X-1, the energy of the absorption line tends to decrease once and then increase with increasing luminosity. I examined double absorption features are formed via gravitational light bending. As a result, I found that the absorption line is likely to be formed via gravitational light bending. That suggests that in Vela X-1 the magnetic field strength becomes 5 times stronger than the value that the energy of the absorption line has implied. I also tried calculating absorption lines in A0535+262. In this object, the characteristics similar to Vela X-1 can be explained by the same model. Thus, the two absorption lines in A0535+262 can be formed by gravitational light bending. Therefore, my simulations suggest that A0535+262 is an object having a superstrong magnetic field over the 13 power of 10.

Academic Significance and Societal Importance of the Research Achievements

宇宙において最も強い磁場を持つ天体の中性子星の磁場強度を直接測定できる唯一の方法であるサイクロトロン吸収線のエネルギーについて、シミュレーションを行った。中性子性の磁極付近で形成される降着円柱内での降着ガスによるドップラー効果と重力による光の曲がる効果を考慮することによって、観測結果と一致する新たな結果を得ることができた。これにより今まで見積もられていた磁場の強度よりも5倍程度強い磁場を持つ可能性について示唆することができた。今後のより詳細な観測データにより、この結果が正しいかどうかがより明確になると予想される。

Report

(5 results)
  • 2022 Annual Research Report   Final Research Report ( PDF )
  • 2021 Research-status Report
  • 2020 Research-status Report
  • 2019 Research-status Report
  • Research Products

    (5 results)

All 2022 2021 2019 Other

All Int'l Joint Research (1 results) Journal Article (3 results) (of which Int'l Joint Research: 2 results,  Peer Reviewed: 3 results) Presentation (1 results)

  • [Int'l Joint Research] Wuhan University(中国)

    • Related Report
      2022 Annual Research Report
  • [Journal Article] Variations in energy of cyclotron lines with double structures formed in line-forming region with bulk motion in accreting X-ray pulsars2022

    • Author(s)
      Osamu Nishimura
    • Journal Title

      PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN

      Volume: 74 Issue: 4 Pages: 961-973

    • DOI

      10.1093/pasj/psac048

    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Relation of Cyclotron Resonant Energy and Luminosity in a Strongly Magnetized Neutron Star GRO J1008-57 Observed by Insight-HXMT2021

    • Author(s)
      X. Chen, W. Wang, Y. M. Tang, Y. Z. Ding, Y. L. Tuo, A. A. Mushtukov, O. Nishimura, S. N. Zhang, M. Y. Ge, L. M. Song, F. J. Lu, S. Zhang, J. L. Qu
    • Journal Title

      The Astrophysical Journal

      Volume: 919 Issue: 1 Pages: 33-40

    • DOI

      10.3847/1538-4357/ac1268

    • Related Report
      2021 Research-status Report
    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Spectral and Timing Analysis of the Accretion-powered Pulsar 4U 1626?67 Observed with Suzaku and NuSTAR2019

    • Author(s)
      Iwakiri Wataru B.、Pottschmidt Katja、Falkner Sebastian、Hemphill Paul B.、F?rst Felix、Nishimura Osamu、Schwarm Fritz-Walter、Wolff Michael T.、Marcu-Cheatham Diana M.、Chakrabarty Deepto、Tomsick John A.、Wilson-Hodge Colleen A.、Bissinger K?hnel Matthias、Terada Yukikatsu、Enoto Teruaki、Wilms J?rn
    • Journal Title

      The Astrophysical Journal

      Volume: 878 Issue: 2 Pages: 121-137

    • DOI

      10.3847/1538-4357/ab1f87

    • Related Report
      2019 Research-status Report
    • Peer Reviewed / Int'l Joint Research
  • [Presentation] 中性子星のサイクロトロン線へのバルクモーションの影響2021

    • Author(s)
      西村 治
    • Organizer
      「~中性子星の観測と理論~研究活性化ワークショップ 2021」
    • Related Report
      2021 Research-status Report

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Published: 2019-04-18   Modified: 2024-01-30  

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