中国物理B ›› 2012, Vol. 21 ›› Issue (5): 57109-057109.doi: 10.1088/1674-1056/21/5/057109

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A possible mechanism for magnetar soft X-ray/γ-ray emission

高志福1 2 3,彭秋和4,王娜1 2,邹志刚5   

  1. 1. Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, China;
    2. Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008, China;
    3. Graduate University of the Chinese Academy of Sciences, Beijing 100080, China;
    4. Department of Astronomy, Nanjing University, Nanjing 210093, China;
    5. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
  • 收稿日期:2011-09-24 修回日期:2012-04-27 出版日期:2012-04-01 发布日期:2012-04-01
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 10773005), the National Basic Research Program of China (Grant No. 2009CB824800), the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX2-YW-T09), and the Key Directional Project of the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant Nos. 10173020, 10673021, 10778631 and 10903019).

A possible mechanism for magnetar soft X-ray/$\gamma$-ray emission

Gao Zhi-Fu(高志福)a)b)c), Peng Qiu-He(彭秋和) d)†, Wang Na(王娜)a)b), and Chou Chih-Kang(邹志刚)e)   

  1. a. Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, China;
    b. Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008, China;
    c. Graduate University of the Chinese Academy of Sciences, Beijing 100080, China;
    d. Department of Astronomy, Nanjing University, Nanjing 210093, China;
    e. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
  • Received:2011-09-24 Revised:2012-04-27 Online:2012-04-01 Published:2012-04-01
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 10773005), the National Basic Research Program of China (Grant No. 2009CB824800), the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX2-YW-T09), and the Key Directional Project of the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant Nos. 10173020, 10673021, 10778631 and 10903019).

摘要: Once the energies of electrons near the Fermi surface obviously exceed the threshold energy of the inverse β decay, electron capture (EC) dominates inside the magnetar. Since the maximal binding energy of the 3P2 neutron Cooper pair is only about 0.048 MeV, the outgoing high-energy neutrons (Ek(n)>60 MeV) created by the EC can easily destroy the 3P2 neutron Cooper pairs through the interaction of nuclear force. In the anisotropic neutron superfluid, each 3P2 neutron Cooper pair has magnetic energy 2μnB in the applied magnetic field B, where μn=0.966× 10-23 erg·G-1 is the absolute value of the neutron abnormal magnetic moment. While being destroyed by the high-energy EC neutrons, the magnetic moments of the 3P2 Cooper pairs are no longer arranged in the paramagnetic direction, and the magnetic energy is released. This released energy can be transformed into thermal energy. Only a small fraction of the generated thermal energy is transported from the interior to the surface by conduction, and then it is radiated in the form of thermal photons from the surface. After highly efficient modulation within the star's magnetosphere, the thermal surface emission is shaped into a spectrum of soft X-rays/γ-rays with the observed characteristics of magnetars. By introducing related parameters, we calculate the theoretical luminosities of magnetars. The calculation results agree well with the observed parameters of magnetars.

关键词: Landau levels, Fermi surface, thermal radiation, heat conduction

Abstract: Once the energies of electrons near the Fermi surface obviously exceed the threshold energy of the inverse β decay, electron capture (EC) dominates inside the magnetar. Since the maximal binding energy of the 3P2 neutron Cooper pair is only about 0.048 MeV, the outgoing high-energy neutrons (Ek(n)>60 MeV) created by the EC can easily destroy the 3P2 neutron Cooper pairs through the interaction of nuclear force. In the anisotropic neutron superfluid, each 3P2 neutron Cooper pair has magnetic energy 2μnB in the applied magnetic field B, where μn=0.966× 10-23 erg·G-1 is the absolute value of the neutron abnormal magnetic moment. While being destroyed by the high-energy EC neutrons, the magnetic moments of the 3P2 Cooper pairs are no longer arranged in the paramagnetic direction, and the magnetic energy is released. This released energy can be transformed into thermal energy. Only a small fraction of the generated thermal energy is transported from the interior to the surface by conduction, and then it is radiated in the form of thermal photons from the surface. After highly efficient modulation within the star's magnetosphere, the thermal surface emission is shaped into a spectrum of soft X-rays/$\gamma$-rays with the observed characteristics of magnetars. By introducing related parameters, we calculate the theoretical luminosities of magnetars. The calculation results agree well with the observed parameters of magnetars.

Key words: Landau levels, Fermi surface, thermal radiation, heat conduction

中图分类号:  (Landau levels)

  • 71.70.Di
71.18.+y (Fermi surface: calculations and measurements; effective mass, g factor)