4 research outputs found
Vortex Creep Against Toroidal Flux Lines, Crustal Entrainment, and Pulsar Glitches
A region of toroidally oriented quantized flux lines must exist in the proton
superconductor in the core of the neutron star. This region will be a site of
vortex pinning and creep. Entrainment of the neutron superfluid with the
crustal lattice leads to a requirement of superfluid moment of inertia
associated with vortex creep in excess of the available crustal moment of
inertia. This will effect constraints on the equation of state. The toroidal
flux region provides the moment of inertia necessary to complement the crust
superfluid with postglitch relaxation behavior fitting the observations.Comment: Published in The Astrophysical Journal Letter
Peculiar Glitch of PSR J1119-6127 and Extension of the Vortex Creep Model
Glitches are sudden changes in rotation frequency and spin-down rate,
observed from pulsars of all ages. Standard glitches are characterized by a
positive step in angular velocity ( ) and a negative
step in the spin-down rate ( ) of the pulsar.
There are no glitch-associated changes in the electromagnetic signature of
rotation-powered pulsars in all cases so far. For the first time, in the last
glitch of PSR J1119-6127, there is clear evidence for changing emission
properties coincident with the glitch. This glitch is also unusual in its
signature. Further, the absolute value of the spin-down rate actually decreases
in the long term. This is in contrast to usual glitch behaviour. In this paper
we extend the vortex creep model in order to take into account these
peculiarities. We propose that a starquake with crustal plate movement towards
the rotational poles of the star induces inward vortex motion which causes the
unusual glitch signature. The component of the magnetic field perpendicular to
the rotation axis will decrease, giving rise to a permanent change in the
pulsar external torque.Comment: accepted by MNRAS, 10 pages, 2 figure
Neutron star dynamics under time dependent external torques
The two component model of neutron star dynamics describing the behaviour of the observed crust coupled to the superfluid interior has so far been applied to radio pulsars for which the external torques are constant on dynamical timescales. We recently solved this problem under arbitrary time dependent external torques. Our solutions pertain to internal torques that are linear in the rotation rates, as well as to the extremely non-linear internal torques of the vortex creep model. Two-component models with linear or nonlinear internal
torques can now be applied to magnetars and to neutron stars in binary systems, with strong variability and timing noise. Time dependent external torques can be obtained from the observed spin-down (or spin-up)time series
Atypical radio pulsations from magnetar SGR 1935+2154
Magnetars are neutron stars with extremely strong magnetic fields, frequently
powering high-energy activity in X-rays. Pulsed radio emission following some
X-ray outbursts have been detected, albeit its physical origin is unclear. It
has long been speculated that the origin of magnetars' radio signals is
different from those from canonical pulsars, although convincing evidence is
still lacking. Five months after magnetar SGR 1935+2154's X-ray outburst and
its associated Fast Radio Burst (FRB) 20200428, a radio pulsar phase was
discovered. Here we report the discovery of X-ray spectral hardening associated
with the emergence of periodic radio pulsations from SGR 1935+2154 and a
detailed analysis of the properties of the radio pulses. The complex radio
pulse morphology, which contains both narrow-band emission and frequency
drifts, has not been seen before in other magnetars, but is similar to those of
repeating FRBs - even though the luminosities are many orders of magnitude
different. The observations suggest that radio emission originates from the
outer magnetosphere of the magnetar, and the surface heating due to the
bombardment of inward-going particles from the radio emission region is
responsible for the observed X-ray spectral hardening.Comment: 47 pages, 11 figure