New Variable Stars in the Globular Cluster NGC 6584

TL;DR

This study identified 69 variable stars in the globular cluster NGC 6584, including new discoveries, and analyzed their properties to classify the cluster's Oosterhoff type and stellar behavior.

Contribution

The paper reports the discovery of 26 new variable stars in NGC 6584 and provides detailed classifications and period analyses, enhancing understanding of the cluster's variable star population.

Findings

Identified 69 variable stars, including 26 new ones.

Classified variables into RRab, RRc, RRe, eclipsing binaries, and long-period types.

Confirmed the cluster as Oosterhoff Type I based on period and amplitude analysis.

Abstract

Using the Southeastern Association for Research in Astronomy 0.6 meter telescope located at Cerro Tololo, we searched for variable stars in the southern globular cluster NGC 6584. We obtained images during 8 nights between 28 May and 6 July of 2011. After processing the images, we used the image subtraction package ISIS developed by Alard (2000)to search for the variable stars. We identified a total of 69 variable stars in our 10x10 arcmin^2 field, including 43 variables cataloged by Millis & Liller (1980) and 26 hereto unknown variables. In total, we classified 46 of the variables as type RRab, with a mean period of 0.56776 days, 15 as type RRc with a mean period of 0.30886 days, perhaps one lower amplitude type RRe, with a period of 0.26482 days, 4 eclipsing binaries, and 3 long period (P > 2 days) variable stars. As many as 15 of the RRab Lyrae stars exhibited the Blazhko Effect. Furthermore, the mean periods of the RR Lyrae types, the exhibited period/amplitude relationship, and the ratio of N_c/(N_ab+N_c) of 0.25 are consistent with an Oosterhoff Type I cluster. Here we present refined periods, V-band light curves, and classifications for each of the 69 variables, as well as a color-magnitude diagram of the cluster.