We report the detection of RR Lyrae variable stars in Crater II , a recently discovered large and diffuse satellite dwarf galaxy of the Milky Way ( MW ) .
Based on B , V time-series photometry obtained with the Korea Microlensing Telescope Network ( KMTNet ) 1.6 -m telescope at CTIO , we identified 83 ab -type and 13 c -type pulsators by fitting template light curves .
The detected RR Lyrae stars are centrally concentrated , which ensures that most of them are members of Crater II .
In terms of the distribution of RRab stars in the period-amplitude diagram , Crater II is clearly different from ultra-faint dwarf ( UFD ) galaxies , but very similar to the two classical MW dwarf spheroidal ( dSph ) galaxies Draco and Carina with Oosterhoff-intermediate ( Oo-int ) properties .
Combined with the mean period of ab -type variables ( \langle P _ { ab } \rangle = 0.631 \pm 0.004 d ) and the c -type fraction ( \sim 0.14 ) in Crater II , this suggests an Oo-int classification for Crater II and implies that its nature is more like a dSph rather than a UFD .
We also estimated the mean metallicity , reddening , and distance of Crater II , from the photometric and pulsation properties of the RR Lyrae stars .
The stellar population model we have constructed indicates that Crater II is dominated by an old population , but is relatively younger than the oldest globular clusters in the MW .
With a lack of high-amplitude short-period RRab stars , Crater II , like most of the other less massive dSphs , is probably not a surviving counterpart of the major building blocks of the MW halo .