Magnetar

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

Super Luminous Ic Supernovae: catching a magnetar by the tail

Abstract: We report extensive observational data for five of the lowest redshift Super-Luminous Type Ic Supernovae (SL-SNe Ic) discovered to date, namely PTF10hgi, SN2011ke, PTF11rks, SN2011kf and SN2012il. Photometric imaging of the transients at +50 to +230 days after peak combined with host galaxy subtraction reveals a luminous tail phase for four of these SL-SNe. A high resolution, optical and near infrared spectrum from xshooter provides detection of a broad He I $\lambda$10830 emission line in the spectrum (+50d) of SN2012il, revealing that at least some SL-SNe Ic are not completely helium free. At first sight, the tail luminosity decline rates that we measure are consistent with the radioactive decay of \co, and would require 1-4M of i to produce the luminosity. These i masses cannot be made consistent with the short diffusion times at peak, and indeed are insufficient to power the peak luminosity. We instead favour energy deposition by newborn magnetars as the power source for these objects. A semi-analytical diffusion model with energy input from the spin-down of a magnetar reproduces the extensive lightcurve data well. The model predictions of ejecta velocities and temperatures which are required are in reasonable agreement with those determined from our observations. We derive magnetar energies of $0.4\lesssim E$($10^{51}$erg) $\lesssim6.9$ and ejecta masses of $2.3\lesssim M_{ej}$(\M) $\lesssim 8.6$. The sample of five SL-SNe Ic presented here, combined with SN 2010gx - the best sampled SL-SNe Ic so far - point toward an explosion driven by a magnetar as a viable explanation for all SL-SNe Ic.

Magnetars: the physics behind observations

Abstract: Magnetars are the strongest magnets in the present universe and the combination of extreme magnetic field, gravity and density makes them unique laboratories to probe current physical theories (from quantum electrodynamics to general relativity) in the strong field limit. Magnetars are observed as peculiar, burst--active X-ray pulsars, the Anomalous X-ray Pulsars (AXPs) and the Soft Gamma Repeaters (SGRs); the latter emitted also three "giant flares," extremely powerful events during which luminosities can reach up to 10^47 erg/s for about one second. The last five years have witnessed an explosion in magnetar research which has led, among other things, to the discovery of transient, or "outbursting," and "low-field" magnetars. Substantial progress has been made also on the theoretical side. Quite detailed models for explaining the magnetars' persistent X-ray emission, the properties of the bursts, the flux evolution in transient sources have been developed and confronted with observations. New insight on neutron star asteroseismology has been gained through improved models of magnetar oscillations. The long-debated issue of magnetic field decay in neutron stars has been addressed, and its importance recognized in relation to the evolution of magnetars and to the links among magnetars and other families of isolated neutron stars. The aim of this paper is to present a comprehensive overview in which the observational results are discussed in the light of the most up-to-date theoretical models and their implications. This addresses not only the particular case of magnetar sources, but the more fundamental issue of how physics in strong magnetic fields can be constrained by the observations of these unique sources.

Magnetar spin-down, hyperenergetic supernovae, and gamma-ray bursts

Abstract: The Kelvin-Helmholtz cooling epoch, lasting tens of seconds after the birth of a neutron star in a successful core-collapse supernova, is accompanied by a neutrino-driven wind. For magnetar-strength (~1015 G) large-scale surface magnetic fields, this outflow is magnetically dominated during the entire cooling epoch. Because the strong magnetic field forces the wind to corotate with the proto-neutron star, this outflow can significantly affect the neutron star's early angular momentum evolution, as in analogous models of stellar winds. If the rotational energy is large in comparison with the supernova energy and the spin-down timescale is short with respect to the time required for the supernova shock wave to traverse the stellar progenitor, the energy extracted may modify the supernova shock dynamics significantly. This effect is capable of producing hyperenergetic supernovae and, in some cases, provides conditions favorable for gamma-ray bursts. We estimate spin-down timescales for magnetized, rotating proto-neutron stars and construct steady state models of neutrino-magnetocentrifugally driven winds. We find that if magnetars are born rapidly rotating, with initial spin periods (P) of ~1 ms, then of order 1051-1052 ergs of rotational energy can be extracted in ~10 s. If magnetars are born slowly rotating (P 10 ms), they can spin down to periods of ~1 s on the Kelvin-Helmholtz timescale.