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Register a new userGravitational Waves from Newborn Accreting Millisecond Magnetars
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Two accretion columns have been argued to form over the surface of a newborn millisecond magnetar for an extremely high accretion rate $gtrsim1.8times10^{-2}M_odot {rm s^{-1}}$ that may occur in the core-collapse of a massive star. In this paper, we investigate the characteristics of these accretion columns and their gravitational wave (GW) radiation. For a typical millisecond magnetar (surface magnetic field strength $Bsim10^{15}$ G and initial spin period $Psim1$ ms), we find (1) its accretion columns are cooled via neutrinos and can reach a height $sim1$ km over the stellar surface; (2) its column-induced characteristic GW strain is comparable to the sensitivities of the next generation ground-based GW detectors within a horizon $sim1$ Mpc; (3) the magnetar can survive only a few tens of seconds; (4) during the survival timescale, the height of the accretion columns increases rapidly to the peak and subsequently decreases slowly; (5) the column mass, characteristic GW strain, and maximum GW luminosity have simultaneous peaks in a similar rise-fall evolution. In addition, we find that the magnetars spin evolution is dominated by the column accretion torque. A possible association with failed supernova is also discussed.
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Accreting Millisecond X-Ray Pulsars (AMXPs) are astrophysical laboratories without parallel in the study of extreme physics. In this chapter we review the past fifteen years of discoveries in the field. We summarize the observations of the fifteen known AMXPs, with a particular emphasis on the multi-wavelength observations that have been carried out since the discovery of the first AMXP in 1998. We review accretion torque theory, the pulse formation process, and how AMXP observations have changed our view on the interaction of plasma and magnetic fields in strong gravity. We also explain how the AMXPs have deepened our understanding of the thermonuclear burst process, in particular the phenomenon of burst oscillations. We conclude with a discussion of the open problems that remain to be addressed in the future.
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