Search for Binary Neutron Stars with Magnetar-Class Strong Magnetic Fields

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K03694
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 16010:Astronomy-related
• Research Institution: The University of Tokyo
• Principal Investigator: Makishima Kazuo 東京大学, 大学院理学系研究科(理学部), 名誉教授 (20126163)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: マグネター / 中性子星 / 強磁場 / 連星系 / 宇宙Ｘ線

Outline of Final Research Achievements

This research aimed at discovering, in binary systems, neutron stars (NS) that have ultra-strong magnetic fields comparable to those of magnetars. The objective has been fulfilled by the following results. (1) We confirmed that the NS in the binary X-ray pulsar system X Persei has a strong dipole filed exceeding 1e14 Gauss. (2) We discovered that the MeV-brightest gamma-ray source LS 5039 contains an NS as its compact component, and the NS has as strong dipole magnetic fields as isolated magnetars.(3) We successfully reinforced the view that isolated magnetars harbor, in their interior, still stronger toroidal magnetic fields reaching 1e16 Gauss. (4) The NSs in X Persei and LS 5039 are both likely to have a mass of about 2.0 Solar masses, which is possibly higher than those of typical NSs.

Free Research Field

Ｘ線宇宙物理学

Academic Significance and Societal Importance of the Research Achievements

本課題は、以下の学術的な意義・波及効果をもつ。(1) マグネター級の双極子磁場をもつNSは連星中にも存在し、それらが特殊な天体ではないことを明かにした。(2) X Perseiと LS 5039で、連星運動から導かれたNSの質量は、典型的な1.4太陽質量よりやや大きく、2.0太陽質量程度である。これはNS内部での核物質の状態方程式にとって、新しい知見である。(3) LS 5039では、超磁場における粒子加速の結果、強いMeV帯のガンマ線が生成されることがわかった。(4)孤立マグネターの内部には、さらに強いトロイダル磁場が普遍的に潜むことを突き止めた。