750- DAYS PHOTOMETRIC AND SPECTRAL VARIABILITY OF THE SYMBIOTIC STAR CH CYG

Abstract

Background: CH Cyg is a bright (V≈8 mag) well-known symbiotic star, which shows unpre-dictable brightness variations on time-scales from minutes to years with amplitudesfrom ∼0.1 mag to a few magnitudes. CH Cyg is active in different spectral ranges:from X-rays to radio. Leahy & Taylor (1987) detected X-ray radiation from the star with maximalocated in the soft X-ray (<2 keV) and hard (>10 keV) energies. CH Cyg is alsoa well known source of a collimated bipolar mass outflow, detected in the radio(e.g., Taylor et al. 1986; Crocker at al. 2001). Materials and Method: The characteristic size of the jetswas about 1400 au, and their space velocity was ∼700 km/s. Recently, CH Cygjets were detected also in X-rays (e.g., Galloway & Sokoloski 2004; Karovska et al. 2007). Interferometric image of CH Cyg showed two components of the system with aseparation of 0.042′′ (Mikolajewska et al. 2010). Hinkle (2009) derive the orbitalperiod of the binary as 15.6 yr with the component masses 0.7 M⊙  and 2 M⊙ for the primary and the secondary, respectively. Results: The light curve of the symbiotic star CH Cyg was created during the period of 1963–2021 using the AAVSO collection of photometric observations. With the exception of the time of the starburst, analysis of the light curve revealed that all minima correlate to fluctuations of around 750 days. Fourier scargle analysis was used to periodically analyze the brightness and radial velocities of absorption lines. Conclusion: The light curves for the periods 1966–1976 and 2000–2005 showed a period of 750 days, which matched the star's relatively quiet condition, and 751 days for the velocities of the red giant's absorption lines. The light curve is 0.30 phases behind the radial-velocity curve.