Mid-Cycle Observations of CR Boo and Estimation of the System’s Parameters

We present observations (with NAO Rozhen and AS Vidojevica telescopes) of the AM Canum Venaticorum (AM CVn) binary star CR Bootis (CR Boo) in the UBV bands. The data were obtained in two nights in July 2019, when the V band brightness was in the range of 16.1–17.0 mag. In both nights, a variability for a period of 25 ± 1 min and amplitude of about 0.2 magnitudes was visible. These brightness variations are most likely indications of “humps”. During our observational time, they appear for a period similar to the CR Boo orbital period. A possible reason of their origin is the phase rotation of the bright spot, placed in the contact point of the infalling matter and the outer disc edge. We estimated some of the parameters of the binary system, on the base of the observational data.