Exploratory Spectroscopy of Magnetic Cataclysmic Variables Candidates and Other Variable Objects

TL;DR

This study used optical spectroscopy of variable objects from CRTS to identify new magnetic Cataclysmic Variables, increasing the known population and demonstrating an efficient, cost-effective discovery method.

Contribution

It presents the first large spectroscopic survey targeting CRTS-selected variables to find magnetic CVs, discovering 13 new candidates and validating variability-based selection.

Findings

Identified 13 new mCV candidates among 45 objects.

Increased known polars by 4% and IPs by 12%.

Spectroscopy combined with variability selection is effective for discovering mCVs.

Abstract

The increasing number of synoptic surveys made by small robotic telescopes, such as the photometric Catalina Real-Time Transient Survey (CRTS), represents a unique opportunity for the discovery of variable sources and improves the statistical samples of such classes of objects. Our goal is the discovery of magnetic Cataclysmic Variables (mCVs). These are rare objects, which probe interesting accretion scenarios controlled by the white dwarf magnetic field. In particular, improved statistics of mCVs would help to address open questions on their formation and evolution. We performed an optical spectroscopy survey to search for signatures of magnetic accretion in 45 variable objects selected mostly from the CRTS. In this sample we found 32 CVs, 22 being mCV candidates from which 13 are previously unreported as such. If the proposed classifications are confirmed, it would represent an increase of 4% in the number of known polars and 12% in the number of known IPs. A fraction of our initial sample was classified as extragalactic sources or other types of variable stars by the inspection of the identification spectra. Despite the inherent complexity in identifying a source as a mCV, variability-based selection followed by spectroscopic snapshot observations has proved to be an efficient strategy for their discoveries, being a relatively inexpensive approach in terms of telescope time.