Dwarf spheroidal satellites of M31: I. Variable stars and stellar
  populations in Andromeda XIX
  We present B,V time-series photometry of Andromeda XIX (And XIX), the most
extended (half-light radius of 6.2') of Andromeda's dwarf spheroidal
companions, that we observed with the Large Binocular Cameras at the Large
Binocular Telescope. We surveyed a 23'x 23' area centered on And XIX and
present the deepest color magnitude diagram (CMD) ever obtained for this
galaxy, reaching, at V~26.3 mag, about one magnitude below the horizontal
branch (HB). The CMD shows a prominent and slightly widened red giant branch,
along with a predominantly red HB, which, however, extends to the blue to
significantly populate the classical instability strip. We have identified 39
pulsating variable stars, of which 31 are of RR Lyrae type and 8 are Anomalous
Cepheids (ACs). Twelve of the RR Lyrae variables and 3 of the ACs are located
within And XIX's half light radius. The average period of the fundamental mode
RR Lyrae stars (<Pab> = 0.62 d, \sigma= 0.03 d) and the period-amplitude
diagram qualify And XIX as an Oosterhoff-Intermediate system. From the average
luminosity of the RR Lyrae stars (<V (RR)> = 25.34 mag, \sigma= 0.10 mag) we
determine a distance modulus of (m-M)$_0$=$24.52\pm0.23$ mag in a scale where
the distance to the Large Magellanic Cloud (LMC) is $18.5\pm0.1$ mag. The ACs
follow a well defined Period-Wesenheit (PW) relation that appears to be in very
good agreement with the PW relationship defined by the ACs in the LMC.
