Periods of outbursts and standstills and parameters variations in two Z Cam stars: Z Cam and AT Cnc

TL;DR

This study analyzes brightness variations, color indices, and system parameters of two Z Cam stars, Z Cam and AT Cnc, revealing periodic oscillations during standstills and differences in their accretion activity.

Contribution

It provides detailed observational analysis of two Z Cam stars, including brightness oscillations, color temperature, and system parameters, highlighting differences in their accretion disk activity.

Findings

Periodic brightness oscillations observed in AT Cnc during standstill.

Z Cam is hotter and has a more active accretion disk than AT Cnc.

Color temperature varies during outburst and standstill states.

Abstract

We present our results on two Z Cam stars: Z Cam and AT Cnc. We apply observational data for the periods that cover the states of outbursts and standstills, which are typical for this type of objects. We report an appearance of periodic oscillations in brightness during the standstill in AT Cnc, with small amplitude variations of 0.03 - 0.04 mag and periodicity of $\approx 20-30$ min. Based on the estimated derredened color index (B - V )0, we calculate the color temperature for both states of the two objects. During the transition from the outbursts to the standstill's state Z Cam varies from bluer to redder, while AT Cnc stays redder in both states. We calculate some of the stars' parameters as: the radii of the primary and secondary components, and the orbital separation for both objects. We construct the profiles of the effective temperature in the discs of the two objects. Comparing the parameters of both systems, we see that Z Cam is definitely the hotter object and we conclude it has a more active accretion disk.