Emission line tomography of the short period cataclysmic variables CC Scl and V2051 Oph

TL;DR

This study evaluates Doppler tomography methods using time-series spectroscopy of two short period cataclysmic variables, demonstrating improved system parameter estimation and validation against traditional techniques.

Contribution

The paper introduces the use of Ca II triplet lines and Monte-Carlo methods in Doppler tomography to enhance orbital parameter constraints in evolved cataclysmic variables.

Findings

Ca II triplet lines provide superior diagnostics for emission components.

Doppler tomography methods yield system parameters consistent with traditional methods.

Validated new techniques with V2051 Oph's eclipse solution.

Abstract

We present time-series spectroscopy of two short period cataclysmic variables, CC Scl and V2051 Oph, to test the efficiency of Doppler tomography-based methods in constraining orbital parameters of evolved cataclysmic variables. We find that the Ca~II triplet lines offer superior diagnostics, revealing emission components from the mass donors and sharp images of the accretion discs. Furthermore, we use Monte-Carlo methods to estimate the uncertainties from ensembles of Doppler maps. We compare our new methods against traditional radial velocity methods and show that they offer a valid route towards system parameter determination. Our analysis of CC Scl suggests a low mass ratio of $q=0.08\pm0.03$ with a primary velocity of $K_1=37\pm14$ km/s. This mass ratio is in between the pre- and post-period minimum status, however our $K_1$ solution favours a post-period minimum system. Our derived parameters for V2051 Oph ($q= 0.16\pm 0.03$, $K_1=97\pm10$ km/s) are in agreement with the eclipse solution ($q=0.19\pm0.03$), offering a direct validation of our methods.