(-0.5,0)

  Source                  Temp (K)    Z ([$M_{\odot}$]{})
  --------- ---------------------- ----------------------
  J030556     7210$^{+270}_{-230}$   -0.5$^{+0.4}_{-2.3}$
  J120709     7310$^{+480}_{-350}$   -2.1$^{+1.8}_{-3.3}$
  J135646     7750$^{+270}_{-240}$   -1.1$^{+0.6}_{-3.5}$
  J135912     7210$^{+200}_{-290}$   -2.1$^{+1.0}_{-2.1}$
  J160103     7410$^{+310}_{-360}$   -1.1$^{+1.1}_{-4.0}$
  J175816     7830$^{+680}_{-400}$   -1.0$^{+0.9}_{-4.7}$
  J175836     7890$^{+280}_{-230}$   -1.3$^{+1.1}_{-3.6}$

  : The temperature and metallicity for seven of our sources derived from model fits to their optical spectra. The errors refer to the 3$\sigma$ confidence interval.

(14,10) (-3,0)

The nature of the variable sources {#nature}
==================================

We have presented evidence that the majority of sources described in this paper are blue compact stellar pulsators. To place our sources in the general context of blue stellar pulsators, we used the most recent edition of the General Catalogue of Variable Stars (GCVS, Samus et al 2009) to determine the distribution of periods in different classes of short period pulsating variables. SX Phe and $\delta$ Sct stars and the longer period pulsating sdB stars all have a distribution of pulsation periods which include periods less than 60 mins. In contrast, RR Lyr and classical Cepheids have much longer pulsation periods. The $\beta$ Cepheid stars have a minimum period of $\sim$2 hrs. The GCVS notes 131 field $\delta$ Sct stars and 20 SX Phe stars.

SX Phe stars and $\delta$ Sct stars have temperatures 