Abstract
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.
Highlights
Introduction and Object DetailsCR Bootis (CR Boo) is a member of the AM Canum Venaticorum (AM CVn) stars group
CR Boo is a member of the AM CVn stars group
The observations were obtained with the 2.0 m telescope of the National Astronomical Observatory (NAO) Rozhen, Bulgaria, the 50/70 cm Schmidt telescope of NAO Rozhen and 1.4m AS
Summary
The AM CVn stars are short-period binary stars in which a white dwarf accretes helium-rich material from a low-mass donor star. Their orbital periods vary between 5 and 65 min [1,2]. It is similar to SU Uma type dwarf novae—a class of cataclysmic variables (CVs) [18]—where normal outbursts and super outbursts are observed; usually, both are with more than 1 amplitude variation in magnitude, while the latter are long-lasting bursts, from days to weeks. The ”humps”, or ”orbital humps”, are observed in the quiescence state of the cataclysmic variables and AM CVn stars They appear for a period similar to the binary orbital period. In the two sections, we report our observational results of CR Boo, calculate some of the system parameters and shortly discuss the observational effects at the end of Section 3
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