Photometric and Hα observations of LSI+61◦303: detection of a ∼26 day V and JHK band modulation

We present new optical and infrared photometric observations and high resolution Hα spectra of the periodic radio star LSI+61303. The optical photometric data set covers the time interval 1985-1993 and amounts to about a hundred nights. A period of ∼26 days is found in the V band. The infrared data also present evidence for a similar periodicity, but with higher amplitude of variation (0.2). The spectroscopic observations include 16 intermediate and high dispersion spectra of LSI+61303 collected between January 1989 and February 1993. The Hα emission line profile and its variations are analyzed. Several emission line parameters – among them the Hα EW and the width of the Hα red hump – change strongly at or close to radio maximum, and may exhibit periodic variability. We also observe a significant change in the peak separation. The Hα profile of LSI+61303 does not seem peculiar for a Be star. However, several of the observed variations of the Hα profile can probably be associated with the presence of the compact, secondary star.