Evolution implications of neutron star magnetic fields: inferred from pulsars and cyclotron lines of HMXBs
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ORIGINAL ARTICLE
Evolution implications of neutron star magnetic fields: inferred from pulsars and cyclotron lines of HMXBs Chang-Qing Ye1 · De-Hua Wang1 · Cheng-Min Zhang2,3,4 · Zhen-Qi Diao1
Received: 10 July 2019 / Accepted: 6 November 2019 © Springer Nature B.V. 2019
Abstract The evolution of neutron star (NS) magnetic field (B-field) has long been an important topic, which is still not yet settled down. Here, we analyze the NS B-fields inferred by the cyclotron resonance scattering features (CRSFs) for the high mass X-ray binaries (HMXBs) and by the magnetic dipole model for the spin-down pulsars. We find that the Bfields of both the 32 NS-HMXBs and 28 young pulsars with the supernova remnants follow the log-normal distributions, with the average values of 3.4 × 1012 G and 4.1 × 1012 G respectively, which are further verified to come from the same continuous distribution by the statistical tests. These results declaim that the two methods of measuring NS B-fields are reliable for the above two groups of samples. In addition, since the NS-HMXBs have experienced the spin-down phase as the normal pulsars without accretion and then the spin-up phase by accretion, their ages should be about million years (Myrs). Our statistical facts imply that the B-fields of NS-HMXBs have little decayed in their non-accretion spin-down phases of ∼ Myrs, as well as in their accretion phases of ∼0.1 Myrs. Keywords X-rays: binaries · Stars: neutron · Pulsars: general · Magnetic field
B D.-H. Wang 1
School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001, China
2
CAS Key Lab of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
3
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
4
Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Beijing 100012, China.
1 Introduction The magnetic fields (B-fields) of neutron stars (NSs) play the significant roles in many aspects of pulsar phenomena, e.g., the electromagnetic emissions from the radio to high energy wavebands (Harding and Kalapotharakos 2017; Manchester 2017; Becker et al. 2018). Until now, more than 2700 radio pulsars (Lorimer et al. 2019) and over 300 accreting NSs in high/low mass X-ray binaries (HMXBs/LMXBs) (Liu et al. 2007; Walter et al. 2015) have been observed. It is generally accepted that the B-fields of NSs dramatically decay in the binary accretion phase, while those of the isolated NSs should not decay, based on which the low B-field distributions of the double NSs (B ∼ 109 –1010 G, see Yang et al. 2019) and millisecond pulsars (MSPs, B ∼ 107.5 –109 G, see Pan et al. 2018) are very well understood by the binary accretion (Bhattacharya and van den Heuvel 1991; Zhang 2016; van den Heuvel 2017). However, there are still debated issues on the evolutions of NS B-fields: In what extent the B-fields of the isolated NSs have no decay? If the B-fields decay in the accretion phase, can we estimate the extent of the decay for NSs in HMXBs as an i
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