Modeling the wind of the Be star SS 2883

Abstract

Observations of eclipses of the radio pulsar B1259-63 by the disk of its Be-star companion SS 2883 provide an excellent opportunity to study the winds of stars of this type. The eclipses lead to variations in the radio flux (due to variations in the free-free absorption), dispersion measure, rotation measure, and linear polarization of the pulsar. We have carried out numerical modeling of the parameters of the Be-star wind and compared the results with observations. The analysis assumes that the Be-star wind has two components: a disk wind in the equatorial plane of the Be star with a power-law fall-off in the electron density n _e with distance from the center of the star $\rho (n_e \sim \rho ^{ - \beta _o } )$, and a spherical wind above the poles. The parameters for a disk model of the wind are estimated. The disk is thin (opening angle 7.5°) and dense (electron density at the stellar surface n _0e ∼ 10¹² cm⁻³, β ₀ = 2.55). The spherical wind is weak (n _0e ≲ 10⁹ cm⁻³, β ₀ = 2). This is the first comparison of calculated and observed fluxes of the pulsating radio emission.