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

TL;DR

This paper reports optical observations of the AM CVn binary star CR Boo, detecting brightness variations likely caused by phase rotation of the bright spot, and estimates some of its system parameters.

Contribution

It provides new observational data and estimates of system parameters for CR Boo based on recent optical observations.

Findings

Detected 25-minute brightness variations in CR Boo.

Variations likely due to phase rotation of the bright spot.

Estimated some binary system parameters.

Abstract

We present observations (with NAO Rozhen and AS Vidojevica telescopes) of the AM Canum Venaticorum (AM CVn) type 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 $25 (\pm 1)$ 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.