Speaker
Description
The relation between the inner and outer regions of exoplanetary systems is still an open question, for example considering that recent studies are still presenting conflicting results on the relationship between short-period small planets and cold Jupiters. One of the key obstacles to solving this issue is that the most prolific detection techniques so far are strongly biased towards short-period planets: transits can only be observed for close-in planets with the right alignment, while RVs can in principle investigate regions further away from the host star, but require huge time investment and decadal observing campaigns to find Jupiter-like planets. While direct imaging is limited to the study of young stars, astrometry can provide detailed information on the outer regions of planetary systems out to 200pc. The previous Gaia DR3 produced only a limited sample of planetary-mass candidates, limited by the short timespan of the data used and the measurement errors. This will change significantly with Gaia DR4, thanks to double the observations and an order-of-magnitude increase in precision. We present a systematic study of the populations of outer companions around known planetary systems. We perform realistic giant planets (GPs) and brown dwarfs (BDs) signal injection and recovery experiments on simulated Gaia-astrometry time series, over a volume limited (<200 pc) sample of stars with known inner planetary systems (<1AU). In absence of the true Gaia time-series, not yet publicly available, we take advantage of the Gaia Observational Forecast Tool (GOST) to simulate realistic Gaia sampling and scanning law both for DR3 and the incoming DR4. This allows us both to estimate the completeness of the current DR3 exoplanets catalog of outer companions, as well as predict the impact that DR4 will have on this topic, and how it will help solve the current uncertainty on the relationship between inner and outer exoplanet populations.
