X-ray studies of neutron stars and their magnetic fields

Abstract

Utilizing results obtained over the past quarter century mainly with Japanese X-ray astronomy satellites, a review is given to some aspects of neutron stars (NSs), with a particular emphasis on the magnetic fields (MFs) of mass-accreting NSs and magnetars. Measurements of electron cyclotron resonance features in binary X-ray pulsars, using the Ginga and Suzaku observatories, clarified that their surface MFs are concentrated in a narrow range of (1–7) × 108 T. Extensive studies of magnetars with Suzaku reinforced their nature as neutron stars with truly strong MFs, and revealed several important clues to their formation, evolution, and physical states. Taking all these results into account, a discussion is made on the origin and evolution of these strong MFs. One possible scenario is that the MF of NSs is a manifestation of some fundamental physics, e.g., neutron spin alignment or chirality violation, and the MF makes transitions from strong to weak states.

Pulsational Pair-instability Model for Superluminous Supernova PTF12dam:Interaction and Radioactive Decay

“…The effect of line opacity is treated as an expansion opacity according to the prescription of Eastman & Pinto (1993) (see also Blinnikov et al (1998)). The opacity table includes 1.5 × 10 5 spectral lines from Kurucz & Bell (1995) and Verner et al (1996).…”

An application of the Ghosh & Lamb model to the accretion-powered X-ray pulsar X Persei

“…In 2002, the pulsar returned to the spin-up phase, and has since been spinning up until today. This spin up/down alternation implies that the source is close to a torque equilibrium, and hence the long P suggests a strong magnetic field, because we then expect B ∼ L 1 2 P 6 7 (Makishima 2016) In the 2-20 keV range, the spectrum of X Persei can be fitted by a powerlaw model with an exponential cutoff (Di Salvo et al 1998), which is typical of accreting X-ray pulsars. However, in the 20-100 keV band, the spectrum of X Persei is much flatter and harder than those of other X-ray pulsars, and lacks steep cutoff (Sasano 2015).…”

“…The magnetic fields of binary X-ray pulsars have been directly measured utilizing cyclotron resonance scattering features (hereafter CRSF) in their X-ray spectra (e.g., Makishima 2016). The magnetic field strength B measured in this way is distributed in the range of B/(1 + zg) = (1 − 7) × 10 12 G (Yamamoto et al 2014 and references therein), where zg ≃ 0.24 is the gravitational redshift at the neutron-star (hereafter NS) surface.…”

Ground State, Isoelectronic Ions and Low-Lying Excited States of Lithium Atom in Strong Magnetic Field

“…The motivation in this area arises from several sources. On the one hand, this is due to the astrophysical discovery of strong magnetic fields on the surfaces of white dwarfs (10 2 -10 5 T) and neutron stars (10 7 -10 9 T) [4] [5]. Also, the complex properties of atoms under these extreme conditions are of immediate interest from a purely theoretical point of view.…”