摘要：A large number of direct imaging surveys for exoplanets have been performed in recent
years, yielding the first directly imaged planets and providing constraints on the
prevalence and distribution of wide planetary systems. However, like most of the radial
velocity ones, these generally focus on single stars, hence binaries and higher-order
multiples have not been studied to the same level of scrutiny. This motivated the Search
for Planets Orbiting Two Stars (SPOTS) survey, which is an ongoing direct imaging study of
a large sample of close binaries, started with VLT/NACO and now continuing with
VLT/SPHERE. To complement this survey, we have identified the close binary targets in 24
published direct imaging surveys. Here we present our statistical analysis of this
combined body of data. We analysed a sample of 117 tight binary systems, using a combined
Monte Carlo and Bayesian approach to derive the expected values of the frequency of
companions, for different values of the companion’s semi-major axis. Our analysis suggest
that the frequency of sub-stellar companions in wide orbit is moderately low
(≲ 13% with a best value of
6% at 95% confidence level) and not significantly different between single stars and tight
binaries. One implication of this result is that the very high frequency of circumbinary
planets in wide orbits around post-common envelope binaries, implied by eclipse timing,
cannot be uniquely due to planets formed before the common-envelope phase (first
generation planets), supporting instead the second generation planet formation or a
non-Keplerian origin of the timing variations.
