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Magnetar

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


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TL;DR: In this paper, the radio magnetar PSR J1622-4950 was observed at different frequency bands from 1.4 to 17 GHz, and it was shown that although its flux density can vary up to a factor of 10 within a few days, it has on average decreased by approximately a 2 factor over the last 700 days.
Abstract: Here we report on observations of the radio magnetar PSR J1622-4950 at frequencies from 1.4 to 17 GHz. We show that although its flux density is varying up to a factor of ~10 within a few days, it has on average decreased by a factor of 2 over the last 700 days. At the same time, timing analysis indicates a trend of decreasing spin-down rate over our entire data set, again of about a factor of 2 over 700 days, but also an erratic variability in the spin-down rate within this time span. Integrated pulse profiles are often close to 100 per cent linearly polarized, but large variations in both the profile shape and fractional polarization are regularly observed. Furthermore, the behaviour of the position angle of the linear polarization is very complex - offsets in both the absolute position angle and the phase of the position angle sweep are often seen and the occasional presence of orthogonal mode jumps further complicates the picture. However, model fitting indicates that the magnetic and rotation axes are close to aligned. Finally, a single pulse analysis has been carried out at four observing frequencies, demonstrating that the wide pulse profile is built up of narrow spikes of emission, with widths that scale inversely with observing frequency. All three of the known radio magnetars seem to have similar characteristics, with highly polarized emission, time-variable flux density and pulse profiles, and with spectral indices close to zero.

88 citations

Journal ArticleDOI
TL;DR: In this paper, a series of two-dimensional magnetohydrodynamic simulations of the rotational core collapse of a magnetized massive star was performed and it was shown that the toroidal magnetic field amplified by the differential rotation becomes strong enough to generate a tightly collimated shock wave along the rotation axis.
Abstract: We perform a series of two-dimensional magnetohydrodynamic simulations of the rotational core collapse of a magnetized massive star. We employ a realistic equation of state and take into account the neutrino cooling by the so-called leakage scheme. In this study we systematically investigate how the strong magnetic field and the rapid rotation affect the propagation of the shock waves. Our results show that in the case of the strong initial poloidal magnetic field, the toroidal magnetic field amplified by the differential rotation becomes strong enough to generate a tightly collimated shock wave along the rotational axis. On the other hand, in the case of the weak initial magnetic field, although the differential rotation amplifies the toroidal magnetic field over the long rotational period, the launched shock wave is weak and the shape of it becomes wider. The former case is expected to be accompanied by the formation of the so-called magnetar. Our models with rapid rotation and strong magnetic field can create a nozzle formed by the collimated shock wave. This might be the analogous situation to the collapsar that is plausible as the central engine of the gamma-ray bursts.

88 citations

Journal ArticleDOI
TL;DR: In this article, the axisymmetric perturbations of a neutron star endowed with a strong magnetic field (magnetars) were studied, considering the coupled oscillations of the core with the solid crust.
Abstract: We study axisymmetric perturbations of neutron star endowed with a strong magnetic eld (magnetars), considering the coupled oscillations of the uid core with the solid crust. We recover discrete oscillations based mainly in the crust and a continuum in the core. We also conrm the presence of \discrete Alfv en modes" in the gap between two contiguous continua (see van Hoven & Levin (2010)) and, in addition, we can resolve some of them also inside the continua. Our results can explain both the lower and the higher observed quasi periodical oscillations (QPOs) in SGR 1806-20 and SGR 1900+14 and put constrains on the mass, radius and crust thickness of the two magnetars.

88 citations

Journal ArticleDOI
TL;DR: In this paper, the torsional Alfv\'en oscillations of relativistic stars with a global dipole magnetic field were investigated via two-dimensional numerical simulations, and it was shown that there exist two families of quasi-periodic oscillations (QPOs) with harmonics at integer multiples of the fundamental frequency.
Abstract: We investigate torsional Alfv\'en oscillations of relativistic stars with a global dipole magnetic field, via two-dimensional numerical simulations. We find that a) there exist two families of quasi-periodic oscillations (QPOs) with harmonics at integer multiples of the fundamental frequency, b) the lower-frequency QPO is related to the region of closed field lines, near the equator, while the higher-frequency QPO is generated near the magnetic axis, c) the QPOs are long-lived, d) for the chosen form of dipolar magnetic field, the frequency ratio of the lower to upper fundamental QPOs is ~0.6, independent of the equilibrium model or of the strength of the magnetic field, and e) within a representative sample of equations of state and of various magnetar masses, the Alfv\'en QPO frequencies are given by accurate empirical relations that depend only on the compactness of the star and on the magnetic field strength. The lower and upper QPOs can be interpreted as corresponding to the edges or turning points of an Alfv\'en continuum, according to the model proposed by Levin (2007). Several of the low-frequency QPOs observed in the X-ray tail of SGR 1806-20 can readily be identified with the Alfv\'en QPOs we compute. In particular, one could identify the 18Hz and 30Hz observed frequencies with the fundamental lower and upper QPOs, correspondingly, while the observed frequencies of 92Hz and 150Hz are then integer multiples of the fundamental upper QPO frequency (three times and five times, correspondingly). With this identification, we obtain an upper limit on the strength of magnetic field of SGR 1806-20 (if is dominated by a dipolar component) between ~3 and $7\times 10^{15}$G. Furthermore, we discuss the implications for the high-density EOS of compact stars. (Abridged)

88 citations

Journal ArticleDOI
TL;DR: In this article, the Parkes multibeam survey of the Galactic plane was used to discover PSR J1847-0130, a radio pulsar with a 6.7-s spin period and a surface dipole magnetic field strength of 9.4x10−13−G.
Abstract: We report the discovery of PSR J1847-0130, a radio pulsar with a 6.7-s spin period, in the Parkes multibeam survey of the Galactic plane. The slowdown rate for the pulsar, 1.3x10^{-12} s/s, is high and implies a surface dipole magnetic field strength of 9.4x10^{13} G. This inferred dipolar magnetic field strength is the highest 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 J1847-0130 which is lower than the luminosities of all but one AXP. 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 creates new challenges for understanding the possible relationship between these two manifestations of young neutron stars.

87 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
2023137
2022292
2021189
2020257
2019142