The variation of T_eq for the exoplanets detectable by Roman in direct imaging: a catalogue of targets

Abstract

The Roman Space Telescope will be the first mission to analyse exoplanets by directly imaging them in reflected starlight. This technique will enable the atmospheric characterization of long-period planets which cannot be studied by current facilities. In this work, we analysed the exoplanet detection yield of the Roman Space Telescope's coronagraph instrument (CGI). For that, we explored the NASA Exoplanet Archive and computed, for all confirmed exoplanets, 10000 possible orbital realizations based on their Keplerian parameters and corresponding uncertainties. We define a planet as Roman-accessible on the basis of the intrument's inner and outer working angles and its minimum planet-to-star constrast (IWA, OWA, Cmin). We adopt for these technical specifications three plausible configurations, labeled as pessimistic, intermediate and optimistic. Our key outputs for each exoplanet are its probability of being Roman-accessible (Paccess), the range of observable phase angles, the evolution of its equilibrium temperature, the number of days per orbit that it is accessible and its transit probability. In the optimistic scenario, we find 26 Roman-accessible exoplanets with Paccess>25% and orbiting stars brighter than V=7 mag. The number of Roman-accessible planets drops to 10 and 3 in the intermediate and pessimistic scenarios, respectively. We find that the orbits of these planets have larger eccentricities than the orbits of those characterized so far in transit. This results in large variations of the equilibrium temperature along the orbit, which may affect the atmospheric structure.