The Polarisation of a Be star is given by the ratio of scattered flux to direct flux, so
quantitatively
 | (1.5) |
Generally the polarisation of a B
e star increases towards shorter wavelengths, yet there is a
decrease in polarisation in the Balmer emission lines (
Poeckert,
1975;
Poeckert et al.,
1979). The
polarisation is thought to be due to a combination of electron scattering and hydrogen
emission and absorption in the circumstellar disc (see
e.g., Coyne and Kruszewski,
1969). The
increase in density in the disc caused by the global-one-armed-oscillation responsible
for V/R variations, which is mirrored by a decrease in density 180
o away in an
azimuthal sense, does not affect the polarisation as the density is globally unchanged
(
Ignace,
2000).
Print
Email
News!