We report the discovery of a large number of short-period variable stars in the dwarf irregular galaxy NGC 6822 , based on deep time-series imaging carried out with the ESO Very Large Telescope .
In particular , we found a modest population of RR Lyrae stars tracing the presence of an old stellar component in NGC 6822 .
Measurements of the average luminosity of RR Lyrae stars provide a new independent estimate of the distance to this galaxy based on a Pop .
II indicator , ( m - M ) _ { 0 } = 23.36 \pm 0.17 .
In addition , our new data show a significant population of small-amplitude , short-period variable stars filling the instability strip starting at luminosities only a few tenths of a magnitude brighter than the RR Lyrae stars .
Given the presence of an extended star formation in NGC 6822 , the faint end of this distribution of short-period variable stars is likely to originate from a population of intermediate-age , metal-poor He-burning stars , younger and more massive than RR Lyrae stars .