Evidence for distinct components of the galactic stellar halo from 838 RR Lyrae stars discovered in the LONEOS-I survey

We present 838 ab-type RR Lyrae stars from the Lowell Observatory Near Earth Objects Survey Phase I (LONEOS-I). These objects cover 1430 deg(2) and span distances ranging from 3 to 30 kpc from the Galactic center. Object selection is based on phased, photometric data with 28-50 epochs. We use this large sample to explore the bulk properties of the stellar halo, including the spatial distribution. The period-amplitude distribution of this sample shows that the majority of these RR Lyrae stars resemble Oosterhoff type I, but there is a significant fraction (26%) which have longer periods and appear to be Oosterhoff type II. We find that the radial distributions of these two populations have significantly different profiles (rho(OoI) similar to R(-2.26 +/- 0.07) and rho(OoII) similar to R(-2.88 +/- 0.11)). This suggests that the stellar halo was formed by at least two distinct accretion processes and supports dual-halo models.