An Halpha-selected sample of cataclysmic variables -- I. Observations of newly discovered systems

TL;DR

This study introduces a new, homogeneous sample of cataclysmic variables selected via Halpha emission, revealing diverse orbital periods and behaviors, which enhances understanding of CV evolution and addresses previous observational biases.

Contribution

The paper presents the discovery and characterization of 14 new CVs selected through Halpha emission, improving sample completeness and diversity compared to previous methods.

Findings

All new CVs have orbital periods above 3 hours.

Presence of eclipsing systems and quasi-periodic modulations observed.

Several CVs resemble nova-like variables and SW Sex stars.

Abstract

Strong selection effects are present in observational samples of cataclysmic variables (CVs), complicating comparisons to theoretical predictions. The selection criteria used to define most CV samples discriminate heavily against the discovery of short-period, intrinsically faint systems. The situation can be improved by selecting CVs for the presence of emission lines. For this reason, we have constructed a homogeneous sample of CVs selected on the basis of Halpha emission. We present discovery observations of the 14 CVs and 2 additional CV candidates found in this search. The orbital periods of 11 of the new CVs were measured; all are above 3 h. There are two eclipsing systems in the sample, and one in which we observed a quasi-periodic modulation on a \sim 1000 s time-scale. We also detect the secondary star in the spectrum of one system, and measure its spectral type. Several of the new CVs have the spectroscopic appearance of nova-like variables (NLs), and a few display what may be SW Sex star behaviour. In a companion paper, we discuss the implications of this new sample for CV evolution.