THE BE X-RAY BINARY LS-I+61-DEGREES-235 RX-J0146.9+6121 - PHYSICAL PARAMETERS AND V/R VARIABILITY/

We present the results of spectroscopic and photometric observations o f LSI + 61 degrees 235. Blue 4100-4900 Angstrom spectra of the system are used to assign a spectral type of B1V to the optical companion whi le detailed uvby beta photometric data permit us to derive its astroph ysical parameters. The monitoring of this high mass X-ray binary since its discovery in 1991 has resulted in the detection of considerable v ariability in the H alpha line profile. The observations cover a compl ete V/R cycle with a period of approximately three years. We discuss m odels which may explain the origin of the variation and conclude that these variations are due to intrinsic changes of the circumstellar env elope rather than being caused by the neutron star. The model which be st fits the observational data is the global one-armed oscillation mod el.