Spirals, shadows & precession in HD 100453 -- I. The orbit of the binary
  In recent years, several protoplanetary discs have been observed to exhibit
spirals, both in scattered light and (sub)millimetre continuum data. The HD
100453 binary star system hosts such a disc around its primary. Previous work
has argued that the spirals were caused by the gravitational interaction of the
secondary, which was assumed to be on a circular orbit, coplanar with the disc
(meaning here the large outer disc, as opposed to the very small inner disc).
However, recent observations of the CO gas emission were found incompatible
with this assumption. In this paper, we run SPH simulations of the gas and dust
disc for seven orbital configurations taken from astrometric fits and compute
synthetic observations from their results. Comparing to high-resolution ALMA
$^{12}$CO data, we find that the best agreement is obtained for an orbit with
eccentricity $e=0.32$ and semi-major axis $a=207$ au, inclined by $61^\circ$
relative to the disc plane. The large misalignment between the disc and orbit
planes is compatible with the tidal evolution of a circumprimary disc in an
eccentric, unequal-mass binary star.
