Roche tomography of cataclysmic variables - VIII: The irradiated and spotted dwarf nova, SS Cygni

TL;DR

This study uses Roche tomography to map the surface of the secondary star in the dwarf nova SS Cygni, revealing high spot coverage, asymmetric irradiation, and complex accretion disc structures, leading to robust system parameters.

Contribution

It applies Roche tomography to SS Cygni, providing the most robust system parameters and detailed surface maps showing spots and irradiation asymmetries.

Findings

Secondary star is highly spotted with asymmetric irradiation.

Strong asymmetric emission from the irradiated secondary star.

Accretion disc exhibits spiral structures.

Abstract

We present the results of our spectroscopic study of the dwarf nova SS Cygni, using Roche tomography to map the stellar surface and derive the system parameters. Given that this technique takes into account the inhomogeneous brightness distribution on the surface of the secondary star, our derived parameters are (in principle) the most robust yet found for this system. Furthermore, our surface maps reveal that the secondary star is highly spotted, with strongly asymmetric irradiation on the inner hemisphere. Moreover, by constructing Doppler tomograms of several Balmer emission lines, we find strong asymmetric emission from the irradiated secondary star, and an asymmetric accretion disc that exhibits spiral structures.