An SX Phe Variable Star in the Distant Galactic Halo

Abstract

ABSTRACT. We report the discovery of a pulsating field star with period 0.060 769 0(1) days, amplitude A y=0.57 mag, mean magnitude {m v )= 18.35, and late-A or early-F spectral type. These characteristics suggest that the star is an SX Phe variable, located approximately 11 kpc away in the Galactic halo. These Population II variables are believed to originate as blue stragglers, and only eight other such field stars, all located in the disk, are known to exist.

δScuti and related stars: Analysis of the R00 Catalogue

“…The other 6 stars (V879 Her, V2314 Oph, BQ Ind, PL 43, BQ Psc and 29499-057) are new and were discovered by Wetterer et al (1996), , Hipparcos catalogue (ESA, 1997), Preston & Landolt (1998), Bernstein et al (1995) and Preston & Landolt (1999), respectively. The position of the field SX Phe stars is also shown in Fig.…”

New catalogue of blue stragglers in open clusters

“…It is worth pointing out that these low-lithium binaries show higher rotational velocities than do stars of the same temperature (Preston & Sneden 2000;Ryan et al 2001;Carney et al 2005). Regarding the link between the SX Phoenicis (SX Phe) variables and field blue stragglers, there is the work by Bernstein et al (1995) on the discovery of one such variable in the halo, and those by Preston & Landolt (1998, where several variables are also found to be binaries. Some metal-poor, main-sequence field-A stars are shown to exhibit thick-disc kinematics (Girard et al 2004), which supports their interpretation of them as thick-disc blue stragglers.…”