Speaker
Dr
Sergei Popov
(SAI Moscow)
Description
Up to now it is unclear how magnetars obtain their large magnetic
fields. In the standard model it is proposed that fields are enhanced
via a dynamo mechanism. This scenario requires that the neutron star
has very rapid initial rotation. Such assumption, on one hand,
requires rapid rotation of the progenitor, and so a specific
evolution; on another hand, this assumption leads us to potentially
testable predictions.
At first we study evolutionary channels in binary evolution which can
produce rapidly rotating massive stellar cores prior to collapse. It
is demonstrated that in an optimistic scenario
one can easily explain the fraction of magnetars among all NSs and
the fact that all known sources of this kind are isolated. In a very
conservative approach the fraction of magnetars is also reproduced,
but it is necessary to assume correlation between initial spin and
kick velocity to explain the absence of companions for known
magnetars.
Then we study evolution of magnetars in close binary systems, and
demonstrate that the observational data is in correspondence with the
standard magnetic field decay scenario.
Finally, we discuss the possibility that some of CCOs are magnetars
which experienced very strong fall-back, in particular we look at the
case of Kes 79 where a NS has relatively long spin period (in
comparison with what is necessary for effective dynamo). A discovery
of an anti-magnetar with a millisecond period and strong crustal field
identifiable, for example, due to large pulse fraction, would be the
proof of the dynamo field origin. Existence of such sources is in
correspondence with the present standard picture of neutron star
unification. However, the fraction of magnetars with submerged fields
can be small --- few percent of the total number of CCOs.
Author
Dr
Sergei Popov
(SAI Moscow)
