We have surveyed Andromeda VI , a dwarf spheroidal galaxy companion to M31 , for variable stars using F450W and F555W observations obtained with the Hubble Space Telescope .
A total of 118 variables were found , with 111 being RR Lyrae , 6 anomalous Cepheids , and 1 variable we were unable to classify .
We find that the Andromeda VI anomalous Cepheids have properties consistent with those of anomalous Cepheids in other dwarf spheroidal galaxies .
We revise the existing period–luminosity relations for these variables .
Further , using these and other available data , we show that there is no clear difference between fundamental and first-overtone anomalous Cepheids in a period-amplitude diagram at shorter periods , unlike the RR Lyrae .
For the Andromeda VI RR Lyrae , we find that they lie close to the Oosterhoff type I Galactic globular clusters in the period-amplitude diagram , although the mean period of the RRab stars , \langle P _ { ab } \rangle = 0.588 d , is slightly longer than the typical Oosterhoff type I cluster .
The mean V magnitude of the RR Lyrae in Andromeda VI is 25.29 \pm 0.03 , resulting in a distance 815 \pm 25 kpc on the Lee , Demarque , & Zinn distance scale .
This is consistent with the distance derived from the I magnitude of the tip of the red giant branch .
Similarly , the properties of the RR Lyrae indicate a mean abundance for Andromeda VI which is consistent with that derived from the mean red giant branch color .