  In this paper we present a model of the Beta Leo debris disc, with an
emphasis on modelling the resolved PACS images obtained as part of the Herschel
key programme DEBRIS. We also present new SPIRE images of the disc at 250
microns, as well as new constraints on the disc from SCUBA-2, mid-IR and
scattered light imaging. Combining all available observational constraints, we
find three possible models for the Beta Leo (HD102647) debris disc: (i) A 2
component model, comprised of a hot component at 2 AU and a cold component from
15-70 AU. (ii) A 3 component model with hot dust at 2 AU, warm dust at 9 AU,
and a cold component from 30-70 AU, is equally valid since the cold emission is
not resolved within 30 AU. (iii) A somewhat less likely possibility is that the
system consists of a single very eccentric planetesimal population, with
pericentres at 2 AU and apocentres at 65 AU. Thus, despite the wealth of
observational constraints significant ambiguities remain; deep mid-IR and
scattered light imaging of the dust distribution within 30 AU seems the most
promising method to resolve the degeneracy. We discuss the implications for the
possible planetary system architecture; e.g., the 2 component model suggests
planets may exist at 2-15 AU, while the 3 component model suggests planets
between 2-30 AU with a stable region containing the dust belt at 9 AU, and
there should be no planets between 2-65 AU in the eccentric planetesimal model.
We suggest that the hot dust may originate in the disintegration of comets
scattered in from the cold disc, and examine all A stars known to harbour both
hot and cold dust to consider the possibility that the ratio of hot and cold
dust luminosities is indicative of the intervening planetary system
architecture.
