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Catalogue of exoplanets accessible in reflected starlight to the Nancy Grace Roman Space Telescope

Ó. Carrión-González, A. García Muñoz, N. C. Santos, J. Cabrera, Sz. Csizmadia, H. Rauer

Context. Reflected starlight measurements will open a new path in the characterization of directly imaged exoplanets. However, we still lack a population study of known targets to which this technique can be applied.

Aims. We investigate which of the about 4300 exoplanets confirmed to date are accessible for the Roman Space Telescope coronagraph in reflected starlight at reference wavelengths λ = 575, 730, and 825 nm. We carry out a population study and also address the prospects for phase-curve measurements.

Methods. We used the NASA Exoplanet Archive as a reference for planet and star properties and explored the effect of their uncertainties on the exoplanet detectability by applying statistical arguments. We defined a planet as Roman-accessible on the basis of the inner and outer working angles of the instrument and its minimum planet-to-star contrast (IWA, OWA, and Cmin). We adopted three plausible configurations for these technical specifications, labeled 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 for which it is accessible, and its transit probability.

Results. In the optimistic scenario, we find 26 Roman-accessible exoplanets with Paccess > 25% and host stars brighter than V = 7 mag. This population is biased towards planets more massive than Jupiter, but also includes the super-Earths tau Cet e and f, which orbit near the habitable zone of their star. Thirteen planets are part of multi-planetary systems. Three of these planets have known transiting companions, which offers opportunities for a contemporaneous atmospheric characterization. The intermediate and pessimistic scenarios yield ten and three Roman-accessible exoplanets, respectively. We find that inclination estimates (e.g. with astrometry) are required to refine the detectability prospects.

Conclusions. A science phase of the coronagraph instrument has a remarkable potential for characterizing the atmospheres of exoplanets that cannot be studied with other techniques.

catalogs; planets and satellites: detection; planets and satellites: fundamental parameters; planets and satellites: gaseous planets; planets and satellites: terrestrial planets; Astrophysics - Earth and Planetary Astrophysics; Astrophysics - Instrumentat

Astronomy & Astrophysics
Volume 651, Article Number A7, Number of pages 31
2021 July

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia