Magnetars from magnetized cores (original) (raw)
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Magnetars From Magnetized Cores Created by a Strong Interaction Phase Transition
Arxiv preprint arXiv:1012.1420, 2010
We consider a model where the strong magnetic fields of magnetars arise from a high baryon density, magnetized core. In this framework magnetars are distinguished from pulsars by their higher masses and central density. For magnetars, as core densities exceed a threshold, the strong interaction induces a phase transition to a ground state that aligns all magnetic moments. The core magnetic field is initially shielded by the ambient high conductivity plasma. With time the shielding currents dissipate transporting the core field out, first to the crust and then breaking through the crust to the surface of the star. Recent observations provide strong support for this model which accounts for several properties of magnetars and also enables us to identify new magnetars.
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.
Magnetic Properties of Star-forming Dense Cores
The Astrophysical Journal, 2021
Magnetic and energetic properties are presented for 17 dense cores within a few hundred pc of the Sun. Their plane-of-sky field strengths "#$ are estimated from the dispersion of polarization directions, following Davis, Chandrasekhar and Fermi (DCF). Their ratio of mass to magnetic critical mass is 0.5 ≲ * ⁄ ≲ 3, indicating nearly critical field strengths.
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.
On the Origin of Pulsar and Magnetar Magnetic Fields
The Astrophysical Journal, 2022
In order to address the generation of neutron star magnetic fields, with particular focus on the dichotomy between magnetars and radio pulsars, we consider the properties of dynamos as inferred from other astrophysical systems. With sufficiently low (modified) Rossby number, convective dynamos are known to produce dipole-dominated fields whose strength scales with convective flux, and we argue that these expectations should apply to the convective protoneutron stars (PNSs) at the centers of core-collapse supernovae. We analyze a suite of three-dimensional simulations of core collapse, featuring a realistic equation of state and full neutrino transport, in this context. All our progenitor models, ranging from 9 M ⊙ to 25 M ⊙, including one with initial rotation, have sufficiently vigorous PNS convection to generate dipole fields of order ∼1015 Gauss, if the modified Rossby number resides in the critical range. Thus, the magnetar/radio pulsar dichotomy may arise naturally in part from...
Astrophysics and Space Science, 2007
Two classes of high-energy sources, the Soft Gamma Repeaters and the Anomalous X-ray Pulsars are believed to contain slowly spinning "magnetars", i.e. neutron stars the emission of which derives from the release of energy from their extremely strong magnetic fields (> 10 15 G). The enormous energy liberated in the 2004 December 27 giant flare from SGR 1806-20 (∼ 5 × 10 46 erg), together with the likely recurrence time of such events, points to an internal magnetic field strength of ≥ 10 16 G. Such strong fields are expected to be generated by a coherent α − Ω dynamo in the early seconds after the Neutron Star (NS) formation, if its spin period is of a few milliseconds at most. A substantial deformation of the NS is caused by such fields and, provided the deformation axis is offset from the spin axis, a newborn millisecond-spinning magnetar would thus radiate for a few days a strong gravitational wave signal the frequency of which (∼ 0.5 − 2 kHz range) decreases in time. This signal could be detected with Advanced LIGO-class detectors up to the distance of the Virgo cluster, where ≥ 1 yr −1 magnetars are expected to form. Recent X-ray observations revealed that SNRs around magnetar candidates do not appear to have received a larger energy input than in standard SNRs (Vink & Kuiper 2006). This is at variance with what would be expected if the spin energy of the young, millisecond NS were radiated away as electromagnetic radiation andd/or relativistic particle winds. In fact, such energy would be transferred quickly and efficiently to the expanding gas shell. This may thus suggest that magnetars did not form with the expected very fast initial spin. We show here that these findings can be reconciled
Early evolution of newly born magnetars with a strong toroidal field
Monthly Notices of the Royal Astronomical Society, 2009
We present a state-of-the-art scenario for newly born magnetars as strong sources of Gravitational Waves (GWs)in the early days after formation. We address several aspects of the astrophysics of rapidly rotating, ultramagnetized neutron stars (NSs), including early cooling before transition to superfluidity, the effects of the magnetic field on the equilibrium shape of NSs, the internal dynamical state of a fully degenerate, oblique rotator and the strength of the electromagnetic torque on the newly born NS. We show that our scenario is consistent with recent studies of SNRs surrounding AXPs and SGRs in the Galaxy that constrain the electromagnetic energy input from the central NS to be 10 51 erg . We further show that if this condition is met, then the GW signal from such sources is potentially detectable with the forthcoming generation of GW detectors up to Virgo cluster distances where an event rate ∼ 1/yr can be estimated . Finally, we point out that the decay of an internal magnetic field in the 10 16 G range couples strongly to the NS cooling at very early stages, thus significantly slowing down both processes: the field can remain this strong for at least 10 3 yrs, during which the core temperature stays higher than several ×10 8 K.
Understanding the low magnetic field magnetar, SGR 0418+5279, from a magnetized core model
Monthly Notices of the Royal Astronomical Society: Letters, 2012
We consider the newly found low magnetic field magnetar, SGR 0418+5279, which exhibits flares, in the context of a model recently proposed by us in which magnetars owe their strong magnetic fields to a high baryon density, magnetized core. We calculate the characteristic core size which will give rise to a surface polar field of about 10 13 G, observed for this magnetar. We then estimate the time of transport of the magnetic field to the crust by ambipolar diffusion, and find this time to be roughly consistent with the spin-down age of SGR 0418+5279. Our model suggests that a precise post-flare timing analysis for this magnetar would show a persistent increase in the spin-down rate ofν, as observed, for example, in PSR 1846−0258, and in due course a decrease in the braking index, consistent with a post-flare increase in the surface field.
Magnetars and many of the magnetar-related objects are summarized together and discussed. It is shown that there is an abuse of language in the use of "magnetar". Anomalous X-ray pulsars and soft gamma-ray repeaters are well-known magnetar candidates. The current so called anti-magnetar (for central compact objects), accreting magnetar (for superslow X-ray pulsars in high mass X-ray binaries), and millisecond magnetar (for the central engine of some gamma-ray bursts), they may not be real magnetars in present understandings. Their observational behaviors are not caused by the magnetic energy. Many of them are just neutron stars with strong surface dipole field. A neutron star plus strong dipole field is not a magnetar. The characteristic parameters of the neutron stars for the central engine of some gamma-ray bursts are atypical from the neutron stars in the Galaxy. Possible signature of magnetic activities in accreting systems are discussed, including repeated bursts and a hard X-ray tail. China's future hard X-ray modulation telescope may contribute to finding some magnetic activities in accreting neutron star systems.