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New short-period stellar pulsators at large Galactocentric distances
Ramsay, Gavin; Napiwotzki, Ralf; Barclay, Thomas; Hakala, Pasi; Potter, Stephen; Cropper, Mark
AA(Armagh Observatory, College Hill, Armagh BT61 9DG), AB(Centre for Astrophysics Research, STRI, University of Hertfordshire, Hatfield AL10 9AB), AC(Armagh Observatory, College Hill, Armagh BT61 9DG; Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT), AD(Finnish Centre for Astronomy with ESO, University of Turku, Väisäl äntie 20, FI-21500 PIIKKIÖ, Finland), AE(South African Astronomical Observatory, PO Box 9, Observatory 7935, Cape Town, South Africa), AF(Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT)
Monthly Notices of the Royal Astronomical Society, Volume 417, Issue 1, pp. 400-407. (MNRAS Homepage)
Publication Date:
Astronomy Keywords:
surveys, stars: evolution, stars: variables: delta Scuti, Galaxy: halo
Abstract Copyright:
© 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
Bibliographic Code:


We report the discovery of 31 blue, short-period, pulsators made using data taken as part of the Rapid Temporal Survey (RATS). We find that they have periods between 51 and 83 min and full amplitudes between 0.05 and 0.65 mag. Using the period-luminosity relationship for short-period pulsating stars, we determine their distance. Assuming that they are pulsating in either the fundamental or first overtone radial mode the majority are located at a distance greater than 3 kpc, with several being more than 20 kpc distant. Most stars are at least 1 kpc distant from the Galactic plane, with three being more than 10 kpc. One is located in the direction of the Galactic anticentre and has a Galactocentric distance of ˜30 kpc and is ˜20 kpc below the plane: they are therefore potential tracers of the Galactic structure. We have obtained low-resolution spectra for a small number of our targets and find that they have temperatures between 7200 and 7900 K and a metal content less than solar. The colours of the pulsators and the spectral fits to those stars for which we have spectra indicate that they are either SX Phe or delta Scuti stars. We estimate the number of SX Phe stars in our Galaxy and find significantly fewer per unit mass than reported in massive globular clusters or dwarf spheroidal galaxies.
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