THE FUNDAMENTAL PLANE FOR RADIO MAGNETARS (original) (raw)
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Explaining radio emission of magnetars via rotating and oscillating magnetospheres of neutron stars
Monthly Notices of the Royal Astronomical Society, 2012
We investigate the conditions for radio emission in rotating and oscillating magnetars, by focusing on the main physical processes determining the position of their death-lines in the P−Ṗ diagram, i.e. of those lines that separate the regions where the neutron star may be radioloud or radio-quiet. After using the general relativistic expression for the electromagnetic scalar potential in the magnetar magnetosphere, we find that larger compactness parameters of the star as well as larger inclination angles between the rotation axis and the magnetic moment produce death-lines well above the majority of known magnetars. This is consistent with the observational evidence of no regular radio emission from the magnetars in the frequency range typical for the ordinary pulsars. On the contrary, when oscillations of the magnetar are taken into account, the death-lines shift downward and the conditions necessary for the generation of radio emission in the magnetosphere are met. Present observations showing a close connection between the burst activity of magnetars and the generation of the radio emission in the magnetar magnetosphere are naturally accounted for within our interpretation.
Discovery of Two High Magnetic Field Radio Pulsars
Astrophysical Journal, 2000
We report the discovery of two young isolated radio pulsars with very high inferred magnetic Ðelds. PSR J1119[6127 has period P \ 0.407 s, and the largest period derivative known among radio pulsars, Under standard assumptions these parameters imply a characteristic spin-down age of P0 \ 4.0 ] 10~12. only kyr and a surface dipole magnetic Ðeld strength of B \ 4.1 ] 1013 G. We have measured a q c \ 1.6 stationary period second derivative for this pulsar, resulting in a braking index of n \ 2.91^0.05. We have also observed a glitch in the rotation of the pulsar, with fractional period change *P/ P \ [4.4 ] 10~9. Archival radio imaging data suggest the presence of a previously uncataloged supernova remnant centered on the pulsar. The second pulsar, PSR J1814[1744, has P \ 3.975 s and P0 \ 7.4 ] 10~13. These parameters imply kyr, and B \ 5.5 ] 1013 G, the largest of any known radio q c \ 85 pulsar.
On the Origin of Radio Emission from Magnetars
The Astrophysical Journal, 2015
Magnetars are the most magnetized objects in the known universe. Powered by the magnetic energy, and not by the rotational energy as in the case of radio pulsars, they have long been regarded as a completely different class of neutron stars. The discovery of pulsed radio emission from a few magnetars weakened the idea of a clean separation between magnetars and normal pulsars. We use the partially screened gap (PSG) model to explain radio emission of magnetars. The PSG model requires that the temperature of the polar cap is equal to the so-called critical value, i.e. the temperature at which the thermal ions outflowing from the stellar surface screen the acceleration gap. We show that a magnetar has to fulfill the temperature, power and visibility conditions in order to emit radio waves. Firstly, in order to form PSG, the residual temperature of the surface has to be lower than the critical value. Secondly, since the radio emission is powered by the rotational energy, it has to be high enough to enable heating of the polar cap by backstreaming particles to the critical temperature. Finally, the structure of the magnetic field has to be altered by magnetospheric currents in order to widen a radio beam and increase the probability of detection. Our approach allows us to predict whether a magnetar can emit radio waves using only its rotational period, period derivative, and surface temperature in the quiescent mode.
PSR J1847-0130: A Radio Pulsar with Magnetar Spin Characteristics
Astrophysical Journal, 2003
We report the discovery of PSR J1847Ϫ0130, a radio pulsar with a 6.7 s spin period, in the Parkes Multibeam Pulsar Survey of the Galactic plane. The slowdown rate for the pulsar, s s Ϫ1 , is high and implies a Ϫ12 1.3 # 10 surface dipole magnetic field strength of G. This inferred dipolar magnetic field strength is the highest 13 9.4 # 10 by far among all known radio pulsars and over twice the "quantum critical field" above which some models predict radio emission should not occur. The inferred dipolar magnetic field strength and period of this pulsar are in the same range as those of the anomalous X-ray pulsars, which have been identified as being "magnetars" whose luminous X-ray emission is powered by their large magnetic fields. We have examined archival ASCA data and place an upper limit on the X-ray luminosity of J1847Ϫ0130 that is lower than the luminosities of all but one anomalous X-ray pulsar. The properties of this pulsar prove that inferred dipolar magnetic field strength and period cannot alone be responsible for the unusual high-energy properties of the magnetars and create new challenges for understanding the possible relationship between these two manifestations of young neutron stars.
Magnetic fields of neutron stars in X-ray pulsars
Eprint Arxiv Astro Ph 9908234, 1999
Estimates of the magnetic field of neutron stars in X-ray pulsars are obtained using the hypothesis of the equilibrium period for disk and wind accretion and also from the BATSE data on timing of X-ray pulsars using the observed maximum spin-down rate. Cyclotron lines at energies ≥ 100 keV in several Be-transient are predicted for future observations.
The Astrophysical Journal, 2002
We consider the structure of neutron star magnetospheres threaded by large-scale electrical currents, and the effect of resonant Compton scattering by the charge carriers (both electrons and ions) on the emergent X-ray spectra and pulse profiles. In the magnetar model for the Soft Gamma Repeaters and Anomalous X-ray Pulsars, these currents are maintained by magnetic stresses acting deep inside the star, which generate both sudden disruptions (SGR outbursts) and more gradual plastic deformations of the rigid crust. We construct self-similar force-free equilibria of the current-carrying magnetosphere with a power law dependence of magnetic field on radius, B ∝ r −(2+p) , and show that a large-scale twist of field lines softens the radial dependence of the magnetic field to p < 1. The spindown torque acting on the star is thereby increased in comparison with an orthogonal vacuum dipole. We comment on the -2strength of the surface magnetic field in the SGR and AXP sources, as inferred from their measured spindown rates, and the implications of this model for the narrow measured distribution of spin periods.
Proceedings of 11th INTEGRAL Conference Gamma-Ray Astrophysics in Multi-Wavelength Perspective — PoS(INTEGRAL2016), 2017
We have witnessed a remarkable advancement in the field of magnetars, neutron stars with extremely strong magnetic fields in recent years. The number of magnetar systems has tripled in less than a decade, and almost all known sources exhibited extraordinary observational characteristics, such as extremely energetic giant flares, various timing anomalies (glitches and anti-glitches), sudden X-ray brightening, etc. The latest two sources appended to the family of magnetars are not shy in disseminating their unique features: 1E 161348-5055 is the longest spin period neutron star system, and PSR J1119−6127 is an energetic rotation powered pulsars. Here, we review some of their unique characteristics; in particular, what binds them to the family of magnetars, which is their energetic bursts.
Study of Pulsars and Magnetars
Proceedings of XXXIV edition of the Brazilian Workshop on Nuclear Physics — PoS(XXXIV BWNP), 2012
In the present work, we study some of the physical characteristics of neutron stars, especially the mass-radius relation and chemical compositions of the star within a relativistic model subject to a strong magnetic field. To study the influence of the magnetic field in the stellar interior, we consider altogether four solutions: two different values for the magnetic field to obtain a weak and a strong influence, and two configurations: a family of neutron stars formed only by protons, electrons and neutrons and another family formed by protons, electrons, neutrons, muons and hyperons. In both cases all the particles that constitutes the neutron star are in β equilibrium and the total net charge is zero.
Transient pulsed radio emission from a magnetar
Nature, 2006
Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very bright and highly variable X-ray emission that are believed to be powered by ultra-strong magnetic fields of >1e14 G, according to the 'magnetar' model. The radio pulsations that have been observed from more than 1,700 neutron stars with weaker magnetic fields have never been detected from any of the dozen known magnetars. The X-ray pulsar XTE J1810-197 was revealed (in 2003) as the first AXP with transient emission when its luminosity increased 100-fold from the quiescent level; a coincident radio source of unknown origin was detected one year later. Here we show that XTE J1810-197 emits bright, narrow, highly linearly polarized radio pulses, observed at every rotation, thereby establishing that magnetars can be radio pulsars. There is no evidence of radio emission before the 2003 X-ray outburst (unlike ordinary pulsars, which emit radio pulses all the time), and the flux varies from day to day. The flux at all radio frequencies is approximately equal -- and at >20 GHz XTE J1810-197 is currently the brightest neutron star known. These observations link magnetars to ordinary radio pulsars, rule out alternative accretion models for AXPs, and provide a new window into the coronae of magnetars.