15,458 research outputs found
How to make a mature accreting magnetar
Several candidates for accreting magnetars have been proposed recently by
different authors. Existence of such systems contradicts the standard magnetic
field decay scenario where a large magnetic field of a neutron star reaches
fewG at ages Myr. Among other sources,
the high mass X-ray binary 4U0114+65 seems to have a strong magnetic field
around G. We develop a new Bayesian estimate for the kinematic age
and demonstrate that 4U0114+65 has kinematic age 2.4-5 Myr ( credential
interval) since the formation of the neutron star. We discuss which conditions
are necessary to explain the potential existence of magnetars in accreting
high-mass binaries with ages about few Myrs and larger. Three necessary
ingredients are: the Hall attractor to prevent rapid decay of dipolar field,
relatively rapid cooling of the crust in order to avoid Ohmic decay due to
phonons, and finally, low values of the parameter to obtain long Ohmic time
scale due to impurities. If age and magnetic field estimates for proposed
accreting magnetars are correct, then these systems set the strongest limit on
the crust impurity for a selected sample of neutron stars and provide evidence
in favour of the Hall attractor.Comment: 8 pages, 3 figures, accepted to MNRAS on September 2
Spin-axion coupling
We establish a new covariant phenomenological model, which describes an
influence of pseudoscalar (axion) field on spins of test massive particles. The
model includes general relativistic equations of particle motion and spin
evolution in background pseudoscalar (axion), electromagnetic and gravitational
fields. It describes both the direct spin-axion coupling of the gradient type
and indirect spin-axion interaction mediated by electromagnetic fields. Special
attention is paid to the direct spin-axion coupling caused by the gradient of
the pseudoscalar (axion) field. We show that it describes a spin precession,
when the pseudoscalar (axion) field is inhomogeneous and/or non-stationary.
Applications of the model, which correspond to the three types of four-vectors
attributed to the gradient of the pseudoscalar (axion) field (time-like,
space-like, and null), are considered in detail. These are the spin precessions
induced by relic cosmological axions, axions distributed around spherically
symmetric static objects, and axions in a gravitational wave field,
respectively. We discuss features of the obtained exact solutions and some
general properties of the axionically induced spin rotation.Comment: 15 pages; replaced with the version accepted for publication in Phys.
Rev. D; new Subsection IVB and 13 references are adde
A tale of two populations: Rotating Radio Transients and X-ray Dim Isolated Neutron Stars
We highlight similarities between recently discovered Rotating Radio
Transients and X-ray Dim Isolated Neutron Stars. In particular, it is shown
that X-ray Dim Isolated Neutron Stars have a birthrate comparable to that of
Rotating Radio Transients. On the contrary, magnetars have too low a formation
rate to account for the bulk of the radio transient population. The
consequences of the recent detection of a thermal X-ray source associated with
one of the Rotating Radio Transients on the proposed scenarios for these
sources are also discussed.Comment: 5 pages, accepted to MNRAS Letter
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