Optical monitoring of CI Cam after the X-ray burst on April 1, 1998

Abstract

Results of optical spectral monitoring of CI Cam just after its a unusual bright and rapidly evolving X-ray burst are reported. This star is a symbiotic-type X-ray binary. The X-ray-radio-optical burst and the appearance of relativistic S-shaped SS433-like jets make CI Cam to be a very interesting star. We observed emergence of a high excitation and variable emission line spectrum, with broad components of hydrogen and helium lines and the nebular forbidden line of NII. All this agrees well with the formation of relativistic jets in the burst. It was concluded that the burst resulted in destruction of external stationary accretion disk regions. The peak X-ray luminosity is about 10E+37 erg/s at the adopted distance of 1 kpc. It is well below the Eddington luminosity, which is necessary for jet production in a supercritical accretion disk. We propose that jets were formed in a collimated accretion-ejection process in a strong magnetic field of a neutron star.