AAS 201st Meeting, January, 2003
Session 139. Pulsars: Blowing in the Wind
Oral, Thursday, January 9, 2003, 2:00-3:30pm, 618-619

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[139.02] Using a Neutron Star as a Stellar Wind Probe

P. C. Gregory, C. Neish (University of British Columbia)

LS I+61o303 is a remarkable X-ray and \gamma-ray emitting Be + neutron star binary, with periodic (26.5 day) radio outbursts. A recent Bayesian analysis demonstrates that the orbital phase and peak flux density of the radio outbursts exhibit a 4.6 year periodic modulation. We present a model that accounts for the radio properties of LS I+61o303 in terms of variable accretion by the neutron star in an eccentric orbit embedded within the dense equatorial wind from the rapidly rotating Be star. The neutron star thus acts as a probe of the wind speed and density. The analysis indicates that the 4.6 year modulation in radio properties results from an outward moving density enhancement or shell in the Be star equatorial disk. We propose that each new shell ejection may be triggered by the interaction of a short lived relativistic wind (ejector phase) from the neutron star, with the rapidly rotating Be star.

Our best estimates of the mass accretion rate of the neutron star are in the range ~0.001 to ~0.01 of the Eddington accretion limit. This translates to an expected luminosity range of ~1035 to ~1036 ergs s-1 which is comparable to estimates of the total X-ray and \gamma-ray luminosity for LS I +61o 303.

This research was supported in part by a grant from the Canadian Natural Sciences and Engineering Research Council at the University of British Columbia.

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