The photometric and spectral investigation of CI Camelopardalis, an X-ray transient and B[e] star

TL;DR

This study combines photometric and spectroscopic data of CI Cam from 1998-2001, revealing cyclic variations, jet properties, and stratification in the system's envelope, contributing to understanding its complex behavior.

Contribution

It provides new insights into CI Cam's orbital period, jet orientation, and envelope stratification through combined photometric, spectroscopic, and radio observations.

Findings

Detected a 1100-day cyclic variation likely due to orbital motion.

Confirmed an 11.7-day photometric period with lower amplitude.

Measured jet inclination and velocity, revealing relativistic speeds.

Abstract

We combined the results of UBVR photometry of CI Cam taken at Sternberg Astronomical Institute in 1998--2001, and moderate resolution spectroscopy taken at Special Astrophysical Observatory during the same time period. Photometry as well as fluxes of Balmer emissions and of some Fe II emission lines of CI Cam in quiet state reveal a cyclic variation with the period of $1100\pm50^d$. The variation like this may be due to an orbital motion in a wide pair with a giant star companion that exhibits the reflection effect on its side faced to a compact companion. The V-band photometry also confirms the pre-outburst 11.7 day period found by Miroshnichenko earlier, but with a lower amplitude of 3 per cent. The possibility of identity of this photometric period with the period of jet's rotation in the VLA radio map of the object CI Cam was investigated. The radio map modelling reveals the inclination of the jet rotation axis to the line of sight, $i = 35-40^o$, the angle between the rotation axis and the direction of ejection of the jet, $\theta = 7-10^o$, and jet's spatial velocity of 0.23--0.26c. Equivalent widths and fluxes of various spectral lines show different amplitudes of changes during the outburst, and essentially distinct behaviour in quiescence. Five types of such behaviour were revealed, that indicates the strong stratification of a gas and dust envelope round the system . The time lag of strengthening of 50--250$^d$ in the forbidden line of nitrogen [N II] was found relatively to the X-ray outburst maximum.