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Deep Photometry of the Globular Cluster M5: Distance Estimates from White Dwarf and Main Sequence Stars

Andrew C. Layden·Ata Sarajedini·Ted von Hippel·Adrienne M. Cool
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Abstract

We present deep VI photometry of stars in the globular cluster M5 (NGC 5904) based on images taken with the Hubble Space Telescope. The resulting color-magnitude diagram reaches below V ~ 27 mag, revealing the upper 2-3 magnitudes of the white dwarf cooling sequence, and main sequence stars eight magnitudes and more below the turn-off. We fit the main sequence to subdwarfs of known parallax to obtain a true distance modulus of (m-M)_0 = 14.45 +/- 0.11 mag. A second distance estimate based on fitting the cluster white dwarf sequence to field white dwarfs with known parallax yielded (m-M)_0 = 14.67 +/- 0.18 mag. We couple our distance estimates with extensive photometry of the cluster's RR Lyrae variables to provide a calibration of the RR Lyrae absolute magnitude yielding M_V(RR) = 0.42 +/- 0.10 mag at [Fe/H] = -1.11 dex. We provide another luminosity calibration in the form of reddening-free Wasenheit functions. Comparison of our calibrations with predictions based on recent models combining stellar evolution and pulsation theories shows encouraging agreement. (Abridged)

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Andrew C. Layden, Ata Sarajedini, Ted von Hippel, Adrienne M. Cool. 2005-07-14. Deep Photometry of the Globular Cluster M5: Distance Estimates from White Dwarf and Main Sequence Stars. https://doi.org/10.1086/444407

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