  We perform a combined analysis of recent NEOS and Daya Bay data on the
reactor antineutrino spectrum. This analysis includes approximately 1.5 million
antineutrino events, which is the largest neutrino event sample analyzed to
date. We use a double ratio which cancels flux model dependence and related
uncertainties as well as the effects of the detector response model. We find at
3-4 standard deviation significance level, that plutonium-239 and plutonium-241
are disfavored as the single source for the the so-called 5 MeV bump. This
analysis method has general applicability and in particular with higher
statistics data sets will be able to shed significant light on the issue of the
bump. With some caveat this also should allow to improve the sensitivity for
sterile neutrino searches in NEOS.
