Far-Ultraviolet Observations of RR Lyrae Stars in the Core of NGC 1851

Abstract

There are extraordinarily few far ultraviolet observations of RR Lyrae stars in the literature. We present Hubble Space Telescope FUV (~1600 A) imaging of the core of the globular cluster NGC 1851. Eleven new variables whose light curves are consistent with those of RR Lyr stars are discovered, increasing the total number of RR Lyr known in this cluster by a substantial amount. In agreement with basic physical theory, the observed amplitude of the variables in the FUV is enormous compared with the century of past optical observations, ranging up to 4 mag. HST STIS FUV observations of cluster cores may prove an especially effective means of obtaining a near-complete census of RR Lyr stars, combining high angular resolution, suppression of luminous red stars, and data where the stellar pulsation amplitudes are greatly enhanced. Attention is also drawn to a peculiar blue object in the cluster that is most probably a low mass x-ray binary system in quiescence.

arXiv commentAccepted for publication in The Astronomical Journal, Vol. 128, Nov. 2004, 13 pages, 4 figures, AASTeX v5.0

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• Unveiling the core of the Globular Cluster M15 in the Ultraviolet
• The Horizontal Branch population of NGC 1851 as revealed by the Ultra-violet Imaging Telescope (UVIT)
• The Horizontal Branch of NGC 1851: Constraints from its RR Lyrae Variables
• The Swift/UVOT Stars Survey. II. RR Lyrae Stars in M 3 and M 15
• A Far-UV Variability Survey of the Globular Cluster M80
• The Stripped-Star Ultraviolet Magellanic Cloud Survey (SUMS): The UV Photometric Catalog and Stripped Star Candidate Selection