Monitoring of the Central Region of the Globular Cluster M15 = NGC 7078: New Variable Stars

Abstract

We obtained a series of more than two hundred R-band CCD images for the crowded central (115"x77") region of the metal-poor globular cluster M15 with an angular resolution of 0.5"-0.9" in most images. Optimal image subtraction was used to identify variable stars. Brightness variations were found in 83 stars, 55 of which were identified with known cluster variables and the remaining 28 are candidates for new variables. Two of them are most likely SX Phe variables. The variability type of two more stars is incertain. The remaining stars were tentatively classified as RR Lyrae variables. A preliminary analysis of published data and our results shows that the characteristics of RR Lyrae variables in the densest part (r<35") of the cluster probably change. More specifically, the maximum of the period distribution of first- and second-overtone (RR1, RR2) pulsating stars shifts toward shorter periods; i.e., there is an increase in the fraction of stars pulsating with periods < 0.3d and a deficiency of stars with 0.35d-0.40d. The ratio of the number of these short-period RR Lyrae variables to the number of fundamental-tone (RR0) pulsating variables changes appreciably. We found and corrected the error of transforming the coordinates of variables V128-155 in M15 to the coordinate system used in the catalog of variable stars in globular clusters.

29 pages, 6 figures, 2 tables

References in corpus (5)

• Variable Stars in Galactic Globular Clusters
• Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15: II. Kinematical Analysis and Dynamical Modeling
• Addendum: "Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15: II. Kinematical Analysis and Dynamical Modeling"
• Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15: I. STIS Spectroscopy and WFPC2 Photometry
• A New SX Phe Star in the Globular Cluster M15

Cited by in corpus (5)

• Comparative performance of selected variability detection techniques in photometric time series
• The ubiquitous nature of the Horizontal Branch second U-jump: A link with the Blue Hook scenario?
• A Comprehensive Catalogue of Variable Stars in the field of 47 Tucanae
• The Swift/UVOT Stars Survey. II. RR Lyrae Stars in M 3 and M 15
• The Hubble Catalog of Variables (HCV)