New SX Phoenicis Variables in the Globular Cluster NGC 4833

TL;DR

This paper reports the discovery of 6 new SX Phoenicis variable stars in the globular cluster NGC 4833, expanding the known variable star population and providing detailed classifications and properties.

Contribution

It introduces the first identification of SX Phoenicis stars in NGC 4833 using image subtraction, along with detailed period and classification data.

Findings

Discovered 6 new SX Phoenicis stars in NGC 4833.

Confirmed 17 previously known variables and classified new types.

Indicates the cluster is of Oosterhoff type II based on variable star properties.

Abstract

We report the discovery of 6 SX Phoenicis stars in the southern globular cluster NGC 4833. Images were obtained from January through June 2011 with the Southeastern Association for Research in Astronomy 0.6 meter telescope located at Cerro Tololo Interamerican Observatory. The image subtraction method of Alard & Lupton (1998)was used to search for variable stars in the cluster. We confirmed 17 previously cataloged variables by Demers & Wehlau(1977). In addition to the previously known variables we have identified 10 new variables. Of the total number of confirmed variables in our 10x10 arcmin^2 field, we classified 10 RRab variables, with a mean period of 0.69591 days, 7 RRc, with a mean period of 0.39555 days, 2 possible RRe variables with a mean period of 0.30950 days, a W Ursae Majoris contact binary, an Algol-type binary, and the 6 SX Phoenicis stars with a mean period of 0.05847 days. The periods, relative numbers of RRab and RRc variables, and Bailey diagram are indicative of the cluster being of the Oosterhoff type II. We present the phased-light curves, periods of previously known variables and the periods and classifications of the newly discovered variables, and their location on the color-magnitude diagram.