Ha observations of LSI+61 303. First correlation between compact object and circumstellar disk in the Be/X-ray binaries

Remarkable correlation between the Ha emission line and the radio behaviour of LSI+61 303 (GT 0236+610) over its 4 yr modulation is discovered. The radio outburst peak is shifted with 400 d with respect to the Ha equivalent width. The radio outburst onset varies almost in phase with the changes of Ha. A weak moving component in the Ha is detected. We interpret it as due to a denser region, or bulge, orbiting near to the outer edge of the Ha disk.