Observations of free precession of magnetars and estimation of their internal magnetic fields

2017 Fiscal Year Final Research Report

• Project/Area Number: 15H03653
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• 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)
• Co-Investigator(Kenkyū-buntansha): 中澤 知洋 名古屋大学, 大学院理学系研究科(理学部), 准教授 (50342621)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 中性子星 / マグネター / 自由歳差運動 / 内部磁場 / 宇宙Ｘ線衛星

Outline of Final Research Achievements

Using the Suzaku observatory, we had discovered long-period phase-modulation effects in the hard X-ray pulses from two mangetars. This was interpreted as a result of free precession in neutron stars that are axially deformed by ultra-strong toroidal fields hidden in them. In the present study, we analyzed X-ray data of these two magnetars obtained with the US NuSTAR satellite, and successfully reconfirmed the pulse-phase modulation effects in both objects. However, the modulation amplitudes in these objects were considerably different from those measured with Suzaku. In another magnetar observed with Suzaku in 2010, a similar phase modulation phenomenon in the hard X-ray pulses was discovered at a period of 48 ksec. Using the X-ray data from the MAXI observatory, we studied relations between the X-ray intensities and pulse-peiriod derivatives of various binary X-ray pulsars. Then, the object named X Perses was found to have magnetic fields which are comparable to those of magnetars.

Free Research Field

Ｘ線宇宙物理学