A Far-UV Variability Survey of the Globular Cluster M80

Abstract

We have searched for variable sources in the core region of M80, using far ultra-violet data taken with the Advanced Camera for Surveys on board the Hubble Space Telescope. We found three sources that exhibit strong signs of variability in our data. Among these is source TDK1, which we believe to be an RR Lyrae star that reached maximum brightness during our observations. The light curve shows a >3 mag FUV brightening over the course of ~5 hours, with an estimated peak brightness of ~16.7 mag, followed by a decrease to ~20 mag. Archival optical data obtained with WFPC2 confirm that TDK1 is variable in all wavebands. TDK1's SED is reasonably fit by a star with temperature T(eff)=6700K and radius R=4.2R(sun), consistent with the suggestion that it is an RR Lyrae. Based on the photometric and variability characteristics of the other two variables, we suggest that TDK2 is likely to be an SX Phoenicis star with ~55 minutes period, and TDK3 is likely another RR Lyrae. Finally, we briefly discuss the FUV counterparts to two previously known variables in M80, the classical nova T Sco and the dwarf nova DN1.

12 pages, 9 figures and 3 tables. Accepted for publication in MNRAS.

References in corpus (3)

• A Binary Origin for Blue Stragglers in Globular Clusters
• CCD Photometry of the globular cluster M2. RR Lyrae physical parameters and new variables
• A new method for determining physical parameters of fundamental mode RR Lyrae stars from multicolour light curves

Cited by in corpus (5)

• Far-Ultraviolet Observation of the Globular Cluster NGC 6397
• A multi-wavelength survey of NGC\,6752: X-ray counterparts, two new dwarf novae, and a core-collapsed radial profile
• A Deep Search for Faint Chandra X-ray Sources, Radio Sources, and Optical Counterparts in NGC 6752
• The Swift/UVOT Stars Survey. II. RR Lyrae Stars in M 3 and M 15
• Far-ultraviolet investigation into the galactic globular cluster M30 (NGC 7099): I. Photometry and radial distributions