Spectroscopy and Photometry of Cataclysmic Variable Candidates from the Catalina Real Time Survey

TL;DR

This study reports follow-up spectroscopy and imaging of 36 cataclysmic variable candidates from the CRTS, revealing their spectral characteristics, orbital periods, and biases in detection related to outburst amplitudes and survey cadence.

Contribution

It provides new spectroscopic and photometric data for CRTS CV candidates, including orbital periods and insights into survey biases and the prevalence of uncatalogued CVs.

Findings

Most CVs have short orbital periods below the period gap.

CRTS is biased toward detecting CVs with large outburst amplitudes.

A significant number of CVs remain uncatalogued.

Abstract

The Catalina Real Time Survey (CRTS) has found over 500 cataclysmic variable (CV) candidates, most of which were previously unknown. We report here on followup spectroscopy of 36 of the brighter objects. Nearly all the spectra are typical of CVs at minimum light. One object appears to be a flare star, while another has a spectrum consistent with a CV but lies, intriguingly, at the center of a small nebulosity. We measured orbital periods for eight of the CVs, and estimated distances for two based on the spectra of their secondary stars. In addition to the spectra, we obtained direct imaging for an overlapping sample of 37 objects, for which we give magnitudes and colors. Most of our new orbital periods are shortward of the so-called period gap from roughly 2 to 3 hours. By considering the cross-identifications between the Catalina objects and other catalogs such as the Sloan Digital Sky Survey, we argue that a large number of cataclysmic variables remain uncatalogued. By comparing the CRTS sample to lists of previously-known CVs that CRTS does not recover, we find that the CRTS is biased toward large outburst amplitudes (and hence shorter orbital periods). We speculate that this is a consequence of the survey cadence.