stars but have solar metallicities and more likely to be located in the thin disk (see Breger 2000 for a review). Although $\delta$ Sct-like pulsations have been detected in pre-main sequence stars with periods as short as 18 min (Amado et al 2004), approximately 90 percent of $\delta$ Sct stars have a pulsation period in the range 40 min to 5.3 hrs (cf Table 1, Rodríguez et al 2000). SX Phe and $\delta$ Scu stars have a well defined period-luminosity relationship and can therefore be used as distance indicators and hence map Galactic structure (eg Nemec, Linnell Nemec & Lutz 1993).

Since we took our first set of data in 2003, we have obtained a significant amount of further data (Barclay et al 2011). We therefore have made a systematic search for blue, short period, pulsating stars. Our light curves are typically 2–2.5 hrs in duration, so the longest period we can determine with confidence is less than 2 hrs. For stars with periods shorter than 40 mins, it becomes increasingly difficult to determine the nature of the source based on colour and period information (cf Table 1 and 2, Barclay et al 2011). In this paper, we therefore have 