Ninety-Seven New Variable Stars in ω Centauri

Volume 51 number 2 (2023)

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Douglas Walker

Department of Mathematics, Embry-Riddle University Worldwide; walked35@erau.edu

Michael Albrow

Department of Physics and Astronomy, Private Bag 4800, University of Canterbury, Christchurch, New Zealand; michael.albrow@canterbury.ac.nz

Abstract

High-cadence photometry of the globular cluster NGC 5139 (ω Centauri) was conducted using the ULTRACAM high-speed frame transfer CCD camera at the 8.2-m Very Large Telescope (VLT) at La Silla, Chile. This research employs difference imaging algorithms to produce time-series photometry data to search for new variable stars within the ω Centauri cluster. The search produced the detection of 117 variable type stars, 19 which were identified and recovered from earlier surveys. An additional set of checks against the Strasbourg astronomical Data Center (CDS) and General Catalogue of Variable Stars (GCVS database, Version 2022 June) listed 20 entries, 10 of which were listed as either Horizonal Branch (HB) or Red Giant Branch Stars but not as variables. A single star identified in the CDS is listed as a new RR Lyrae variable. Removing these counts from the 117 identified variables leaves 97 previously unidentified variable stars in ω Centauri. This new variable list includes 5 possible new RR Lyrae types, 13 eclipsing binary type systems, 11 BY Draconis, 3 SX Phoenicis, and 65 variables which have been identified as unknown general Irregular/Semiregular type variables.