Cataclysmic Variables in the Second Year of the Zwicky Transient Facility

Abstract

Using a filter in the GROWTH Marshal based on color and the amplitude and timescale of variability, we have identified 372 objects as known or candidate cataclysmic variables (CVs) during the second year of the operation of the Zwicky Transient Facility. From the available difference imaging data, we found that 93 are previously confirmed CVs and 279 are strong candidates. Spectra of four of the candidates confirm them as CVs by the presence of Balmer emission lines, while one of the four has prominent He II lines indicative of containing a magnetic white dwarf. Gaia EDR3 parallaxes are available for 154 of these systems, resulting in distances from 108-2096 pc and absolute magnitudes in the range of 7.5-15.0, with the largest number of candidates between 10.5 and 12.5. The total numbers are 21% higher than from the previous year of the survey with a greater number of distances available but a smaller percentage of systems close to the Galactic plane. Comparison of these findings with a machine-learning method of searching all the light curves reveals large differences in each data set related to the parameters involved in the search process.

Searching for Cataclysmic Variable Stars in Unidentified X-Ray Sources

“…We search for a possible X-ray counterpart of the selected GAIA sources in (i) the ROSAT all-sky survey bright source catalog (Voges et al 1999), (ii) the second Swift-XRT pointsource catalog (Evans et al 2020), and (iii) XMM-Newton DR-10 source catalog (Webb et al 2020). We select the GAIA sources that are located within 10″ from the center of the X-ray source, and then we remove the sources that have been already identified as a CV or other types of objects by checking the catalogs of CVs (Ritter & Kolb 2003;Coppejans et al 2016;Jackim et al 2020;Szkody et al 2021;Sun et al 2021) and the SIMBAD astronomical database. 8 After selecting the GAIA sources that are potentially associated with unidentified X-ray sources, we cross match them with sources observed by the Zwicky Transient Facility DR-8 objects (hereafter ZTF; Masci et al 2019).…”

“…Numerous efforts to identify new CVs and candidates have been made in previous works, and the number of known CVs is rapidly increasing with recent photometric and spectroscopic all-sky surveys (Ritter & Kolb 1998;Coppejans et al 2016;Sun et al 2021;Szkody et al 2021). The methods of confirming CVs are mainly divided into three types, namely, the observation of dwarfnova outbursts, identification of orbital/WD spin variations in photometric light curves, and confirmation of CV-like spectral properties.…”

The Future of Gamma-Ray Experiments in the MeV-EeV Range

“…Additionally, large time domain surveys such as ZTF Snowmass2021 CF07 Gamma-Ray Experiments [641] and VCRO [642] have been (or soon will be) observing the sky every few days. This will allow us to include additional variability features at different wavelengths into the pipeline, which can help to further differentiate various X-ray source classes (e.g., AGN versus CVs; [643,644]). As new gamma-ray observatories (e.g., COSI, CTA, AMEGO; see Chapter 4; [136,327,645]) come online over the next few years the number of newly discovered gamma-ray sources will continue to climb.…”

A Systematic Search for Short-period Close White Dwarf Binary Candidates Based on Gaia EDR3 Catalog and Zwicky Transient Facility Data

“…In addition to searches from individual observations, one can perform a CWDB search with a larger scale. Several surveys can be used to pick potential CWDB candidates, like the Catalina Real-time Transient Survey (CRTS; Breedt et al 2014), the Global Astrometric Interferometer for Astrophysics (Gaia; Geier et al 2017;El-Badry et al 2021a;Gentile Fusillo et al 2021;Rebassa-Mansergas et al 2021;Torres et al 2022), the Optical Gravitational Lensing Experiment (Wevers et al 2016), the Palomar Transient Factory (van Roestel et al 2017(van Roestel et al , 2018Burdge et al 2019b), the All Sky Automated Survey for SuperNovae (Rivera Sandoval et al 2022), the Transit Exoplanet Survey Satellite (Wang et al 2020;Pichardo Marcano et al 2021;Hernandez et al 2022), the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST; Wang et al 2022b), and most recently the Zwicky Transient Facility (ZTF; Burdge et al 2020aBurdge et al , 2020bCoughlin et al 2020;Ofek et al 2020;Szkody et al 2020;Kupfer et al 2021;Szkody et al 2021;Keller et al 2022;McWhirter & Lam 2022). Repeated observations of the same sources can reveal optical variability, and some of these surveys can be used, and have been used, to determine the periodicity.…”