Magnetic activity and orbital parameters of CC Com based on photometric data, LAMOST low- and medium-resolution spectra

Abstract

In this paper, we present four sets of photometric V RI light curves, and several LAMOST low and medium resolution spectra of contact binary CC Com. We revised the orbital parameters by simultaneously combining with previously published radial velocity measurements using the Wilson-Devinney program. We used light curves at different observational times to obtain the starspot parameters. The values of the starspot radius are variable in short- and long-term scales, and their longitudes are stable. We updated the orbital period change of CC Com, and analyzed the periodic variation. The period of CC Com decreases at a rate of 4.66 (±0.20) × 10−11 d yr−1, which may be due to mass transfer from the secondary component to the primary component. The oscillation of its orbital period with a period of 17.18(0.08) years and amplitude of 0.0018(1) d may be caused by the light time effect (LITE) via a third body of 0.06 M ⊙ dwarf or magnetic activity cycle. Furthermore, we obtained one optical spectrum from the LAMOST survey, which gives the spectral type of CC Com as K7±2V. Strong emissions exist in the Hα, and Ca ii H&K lines in the observed spectrum, indicating strong chromospheric activity on CC Com. In the 12 LAMOST medium-resolution spectra, the EWs of Hα line are variable along the phase and time, which may be a plage or flare event.