Campana, S.; D'Avanzo, P.; Stella, L.; Israel, G. L.; Marconi, G.; Casares, J.; Hynes, Rob; Charles, Phil
Bibliographical reference
INTERACTING BINARIES: Accretion, Evolution, and Outcomes. AIP Conference Proceedings, Volume 797, pp. 81-86 (2005).
Advertised on:
10
2005
Citations
6
Refereed citations
6
Description
Millisecond radio pulsars are neutron stars that have been spun-up by
the transfer of angular momentum during the low-mass X-ray binary phase.
The transition from an accretion-powered to a rotation-powered pulsar
takes place on evolutionary timescales at the end of the accretion
process, however it may also occur sporadically in systems undergoing
transient X-ray activity. We have obtained the first optical spectrum of
the low mass transient X-ray pulsar SAX J1808.4-3658 in quiescence.
Similar to the black widow millisecond pulsar B1957+20, this X-ray
pulsar shows a large optical modulation at the orbital period due to an
irradiated companion star. Using the brightness of the companion star as
a bolometer, we conclude that a very high irradiating luminosity, a
factor of ~ 100 larger than directly observed, must be present in the
system. This most likely derives from a rotation-powered neutron star
that resumes activity during quiescence.