unit mass than reported in massive globular clusters or dwarf spheroidal galaxies.'
author:
- 'Gavin Ramsay$^{1}$, Ralf Napiwotzki$^{2}$, Thomas Barclay$^{1,3}$, Pasi Hakala$^{4}$, Stephen Potter$^{5}$,'
- |
    Mark Cropper$^{3}$\
    $^{1}$Armagh Observatory, College Hill, Armagh, BT61 9DG\
    $^{2}$Centre for Astrophysics Research, STRI, University of Hertfordshire, Hatfield, AL10 9AB\
    $^{3}$Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT\
    $^{4}$Finnish Centre for Astronomy with ESO, University of Turku, Väisäl äntie 20, FI-21500 PIIKKIÖ, Finland\
    $^{5}$South African Astronomical Observatory, P.O. Box 9, Observatory 7935, Cape Town, South Africa\
date: 'Accepted 2011 June 16. Received 2011 June 15; in original form 2011 April 25'
title: New short period stellar pulsators at large Galactocentric distances
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stars: surveys – oscillations – stars: variables (SX Phe stars, $\delta$ Scuti stars) – stars: evolution

Introduction
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Pulsations have been detected from stars on a wide range of timescales, from several tens of seconds in the case of white dwarfs to several years in the case of red-giant stars. These pulsations manifest themselves through a periodic variation of the stellar brightness. Pulsating stars can also be found over a wide range of parameter space (temperature, luminosity) in the HR diagram (eg Jeffery 2008). A detailed 