Magnetar

About: Magnetar is a research topic. Over the lifetime, 2905 publications have been published within this topic receiving 106806 citations.

The Five Year Fermi/GBM Magnetar Burst Catalog

Abstract: Since launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has detected many hundreds of bursts from magnetar sources. While the vast majority of these bursts have been attributed to several known magnetars, there is also a small sample of magnetar-like bursts of unknown origin. Here we present the Fermi/GBM magnetar catalog, giving the results of the temporal and spectral analyses of 440 magnetar bursts with high temporal and spectral resolution. This catalog covers the first five years of GBM magnetar observations, from July 2008 to June 2013. We provide durations, spectral parameters for various models, fluences and peak fluxes for all the bursts, as well as a detailed temporal analysis for SGR J1550-5418 bursts. Finally, we suggest that some of the bursts of unknown origin are associated with the newly discovered magnetar 3XMM J185246.6+0033.7.

Simulations of light curves and spectra for superluminous Type Ic supernovae powered by magnetars

Abstract: Numerous superluminous supernovae (SLSNe) of Type Ic have been discovered and monitored in the last decade. The favored mechanism at their origin is a sustained power injection from a magnetar. This study presents non-local thermodynamic equilibrium time-dependent radiative transfer simulations of various single carbon-rich Wolf-Rayet star explosions influenced by magnetars of diverse properties and covering from a few days to one or two years after explosion. Nonthermal processes are treated; the magnetar-power deposition profile is prescribed; dynamical effects are ignored. In this context, the main influence of the magnetar power is to boost the internal energy of the ejecta on week-long time scales, enhancing the ejecta temperature and ionization, shifting the spectral energy distribution to the near-UV (even for the adopted solar metallicity), creating blue optical colors. Varying the ejecta and magnetar properties introduces various stretches and shifts to the light curve (rise time, peak or nebular luminosity, light curve width). At maximum, all models show the presence of OII and CII lines in the optical, and more rarely OIII and CIII lines. Non-thermal effects are found to be negligible during the high-brightness phase. After maximum, higher energy explosions are hotter and more ionized, and produce spectra that are optically bluer. Clumping is a source of spectral diversity after maximum. Clumping is essential to trigger ejecta recombination and yield the presence of OI, CaII, and FeII lines from a few weeks after maximum until nebular times. The UV and optical spectrum of Gaia16apd at maximum or the nebular spectrum of LSQ14an at +410d are compatible with some models that assume no clumping. However, most observed SLSNe Ic seem to require clumping from early post-maximum to nebular times (e.g., SN2007bi at +46 and +367d; Gaia16apd at +43d).

The spin evolution of nascent neutron stars

Abstract: The loss of angular momentum owing to unstable r-modes in hot young neutron stars has been proposed as a mechanism for achieving the spin rates inferred for young pulsars. One factor that could have a significant effect on the action of the r-mode instability is fallback of supernova remnant material. The associated accretion torque could potentially counteract any gravitational-wave-induced spin-down, and accretion heating could affect the viscous damping rates and hence the instability. We discuss the effects of various external agents on the r-mode instability scenario within a simple model of supernova fallback on to a hot young magnetized neutron star. We find that the outcome depends strongly on the strength of the magnetic field of the star. Our model is capable of generating spin rates for young neutron stars that accord well with initial spin rates inferred from pulsar observations. The combined action of r-mode instability and fallback appears to cause the spin rates of neutron stars born with very different spin rates to converge, on a time-scale of approximately 1 year. The results suggest that stars with magnetic fields ?1013 G could emit a detectable gravitational wave signal for perhaps several years after the supernova event. Stars with higher fields (magnetars) are unlikely to emit a detectable gravitational wave signal via the r-mode instability. The model also suggests that the r-mode instability could be extremely effective in preventing young neutron stars from going dynamically unstable to the bar-mode.

Spatial, temporal, and spectral properties of x-ray emission from the magnetar SGR 0501+4516

Abstract: SGR 0501+4516 was discovered with the Swift satellite on 2008 August 22 after it emitted a series of very energetic bursts Since then, the source was extensively monitored with Swift and the Rossi X-ray Timing Explorer (RXTE) and observed with Chandra and XMM-Newton, providing a wealth of information about its outburst behavior and burst-induced changes of its persistent X-ray emission Here, we report the most accurate location of SGR 0501+4516 (with an accuracy of 011) derived with Chandra Using the combined RXTE, Swift/X-ray Telescope, Chandra, and XMM-Newton observations, we construct a phase-connected timing solution with the longest time baseline (~240 days) to date for the source We find that the pulse profile of the source is energy dependent and exhibits remarkable variations associated with the SGR 0501+4516 bursting activity We also find significant spectral evolution (hardening) of the source persistent emission associated with bursts Finally, we discuss the consequences of the SGR 0501+4516 proximity to the supernova remnant, SNR G1609+26 (HB9)

Oscillations of rotating magnetized neutron stars with purely toroidal magnetic fields

Abstract: We investigate the oscillation spectrum of rotating Newtonian neutron stars endowed with purely toroidal magnetic fields, using a time-evolution code to evolve linear perturbations in the Cowling approximation. The background star is generated by numerically solving the magnetohydrodynamics equilibrium equations and may be non-spherical by virtue of both rotation and magnetic effects; hence, our perturbations and background are fully consistent. Whilst the background field is purely toroidal, the perturbed field is mixed poloidal–toroidal. From Fourier analysis of the perturbations, we are able to identify a number of magnetically restored Alfven (or a) modes. We show that in a rotating star pure inertial and a-modes are replaced by hybrid magneto-inertial modes, which reduce to a-modes in the non-rotating limit and inertial modes in the non-magnetic limit. We show that the r-mode instability is suppressed by magnetic fields in sufficiently slowly rotating stars. In addition, we determine magnetic frequency shifts in the f-mode. We discuss the astrophysical relevance of our results, in particular for magnetar oscillations.