Exploratory Spectroscopy of Magnetic Cataclysmic Variables Candidates and Other Variable Objects

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.

Optical observations and cyclops post-shock region modelling of the polar V348 Pav

“…V348 Pav (= V1956-6034 = SSS1956-60) is one of the mCV candidates selected from the sample in Oliveira et al (2017) for a detailed analysis. This object was first detected by its variability in the SRC-J plates and suggested to be an AM Her system by Drissen et al (1994) for the presence of the He ii 4686 Å (weak) emission line in its spectrum.…”

CTCV J2056-3014: An X-Ray-faint Intermediate Polar Harboring an Extremely Fast-spinning White Dwarf

“…Based on their detection of a short periodicity at 15.4 min from optical photometry and the fact that the system matches a relatively bright X-ray emitter in the ROSAT (PSPC) Bright Source Catalog (0.10±0.02 cts s −1 at 0.1-2.4 keV; Haakonsen & Rutledge 2009), Augusteijn et al (2010) suggested J2056 to be an intermediate polar (IP) candidate, i.e., an asynchronously rotating magnetic white dwarf (WD) accreting matter from a Roche-lobe-filling donor usually via a partial accretion disk (Patterson 1994). Oliveira et al (2017) presented additional optical spectroscopy of the system and pointed out the similarity of its spectrum to the spectral features found in the rare IPs with short orbital periods. These features include Hβ as intense as Hα and weak HeII 4686Å in emission.…”

CTCV J2056-3014: An X-ray-faint Intermediate Polar Harboring An Extremely Fast-spinning White Dwarf

“…Based on their detection of a short periodicity at 15.4 min from optical photometry and the fact that the system matches a relatively bright X-ray emitter in the ROSAT (PSPC) Bright Source Catalog (0.10±0.02 cts s −1 at 0.1-2.4 keV; Haakonsen & Rutledge 2009), Augusteijn et al (2010) suggested J2056 to be an intermediate polar (IP) candidate, i.e., an asynchronously rotating magnetic white dwarf (WD) accreting matter from a Roche-lobe-filling donor usually via a partial accretion disk (Patterson 1994). Oliveira et al (2017) presented additional optical spectroscopy of the system and pointed out the similarity of its spectrum to the spectral features found in the rare IPs with short orbital periods. These features include Hβ as intense as Hα and weak HeII 4686 Å in emission.…”