Journal Article

A far-ultraviolet variability survey of the globular cluster M 80

G. S. Thomson, A. Dieball, C. Knigge, K. S. Long and D. R. Zurek

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 406, issue 2, pages 1084-1093
Published in print August 2010 | ISSN: 0035-8711
Published online July 2010 | e-ISSN: 1365-2966 | DOI:
A far-ultraviolet variability survey of the globular cluster M 80

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We have searched for variable sources in the core region of M 80, using far-ultraviolet (FUV) 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 TDK 1, 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 h, with an estimated peak brightness of ≈16.7 mag, followed by a decrease to ≈20 mag. Archival optical data obtained with Wide-Field Planetary Camera 2 confirm that TDK 1 is variable in all wavebands. TDK 1's spectral energy distribution is reasonably fitted by a star with temperature K and radius , 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 TDK 2 is likely to be an SX Phoenicis star with min period, and TDK 3 is likely another RR Lyrae. Finally, we briefly discuss the FUV counterparts to two previously known variables in M 80, the classical nova T Sco and the dwarf nova DN 1.

Keywords: novae, cataclysmic variables; stars: variables: RR Lyrae; globular clusters: individual: M 80; ultraviolet: stars

Journal Article.  5555 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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