The OmegaWhite survey for Short-Period Variable Stars III: Follow-up Photometric and Spectroscopic Observations

Abstract

We present photometric and spectroscopic follow-up observations of short-period variables discovered in the OmegaWhite survey: a wide-field high-cadence g-band synoptic survey targeting the Galactic Plane. We have used fast photometry on the SAAO 1.0-m and 1.9-m telescopes to obtain light curves of 27 variables, and use these results to validate the period and amplitude estimates from the OmegaWhite processing pipeline. Furthermore, 57 sources (44 unique, 13 also with new light curves) were selected for spectroscopic follow-up using either the SAAO 1.9-m telescope or the Southern African Large Telescope. We find many of these variables have spectra which are consistent with being delta Scuti type pulsating stars. At higher amplitudes, we detect four possible pulsating white dwarf/subdwarf sources and an eclipsing cataclysmic variable. Due to their rarity, these targets are ideal candidates for detailed follow-up studies. From spectroscopy, we confirm the symbiotic binary star nature of two variables identified as such in the SIMBAD database. We also report what could possibly be the first detection of the `Bump Cepheid' phenomena in a delta Scuti star, with OW J175848.21-271653.7 showing a pronounced 22% amplitude dip lasting 3 minutes during each pulsational cycle peak. However, the precise nature of this target is still uncertain as it exhibits the spectral features of a B-type star.

28 pages, 12 figures, 6 tables. Accepted for publication in MNRAS

References in corpus (7)

• The VST Photometric Halpha Survey of the Southern Galactic Plane and Bulge (VPHAS+)
• Deep MMT Transit Survey of the Open Cluster M37 II: Variable Stars
• The population of AM CVn stars from the Sloan Digital Sky Survey
• SDSS J160043.6+074802.9: a very rapid sdO pulsator
• A New Gravitational Wave Verification Source
• A delta Scuti distance to the Large Magellanic Cloud
• The OmegaWhite Survey for short period variable stars II: An overview of results from the first four years

Cited by in corpus (7)

• A census of symbiotic stars in the 2MASS, WISE and Gaia surveys
• Torus model properties of an ultra-hard X-ray selected sample of Seyfert galaxies
• The OmegaWhite survey for short-period variable stars - V. Discovery of an ultracompact hot subdwarf binary with a compact companion in a 44 minute orbit
• Identifying Blue Large Amplitude Pulsators from Gaia DR2 & ZTF DR3
• The OmegaWhite Survey for Short-Period Variable Stars VII: High amplitude, short period blue variables
• The DECam Minute Cadence Survey II: 49 Variables but No Planetary Transits of a White Dwarf
• The OmegaWhite Survey for Short Period Variable Stars VI. Open Clusters