Correcting the effect of stellar spots on ARIEL transmission spectra II.The limb darkening effect

Abstract

This paper is part of an effort to correct the transmission spectra of a transiting planet orbiting an active star. In Paper I (Cracchiolo et al. 2020) we have demonstrated a methodology to minimize the potential bias induced by unocculted star spots on the transmission spectrum, assuming a spot model parameterized by filling factor and temperature. In this work we introduce the limb darkening effect, therefore the position of the spot in the stellar disk and the impact parameter of the transiting planet now play a key role. The method is tested on simulations of planetary transits of three representative kinds of planetary systems, at ARIEL resolution. We find that a realistic treatment of the limb darkening is required to reliably estimate both the spots parameters and the transmission spectrum of the transiting planet. Furthermore, we show that the influence of the spots onthe retrieval of the planetary transmission spectrum is significant for spots close to the center of the star, covering a fraction greater than 0.05 and with a temperature contrast greater than 500 K, and that for these cases our method can confidently extract the transmission spectrum and the impact parameter of the transiting planet for both cases of occulted and not occulted spots, provided that we have an accurate characterization of the stellar parameters and a reliable simulator of the instrument performances.

14 pages, 9 figures

References in corpus (9)

• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Water Vapor in the Spectrum of the Extrasolar Planet HD 189733b: 1. the Transit
• The effect of stellar limb darkening values on the accuracy of the planet radii derived from photometric transit observations
• Five Intermediate-Period Planets from the N2K Sample
• HAT-P-5b: A Jupiter-like hot Jupiter Transiting a Bright Star
• Forecasting the Impact of Stellar Activity on Transiting Exoplanet Spectra
• ArielRad: the Ariel Radiometric Model
• Improvements on analytic modelling of stellar spots
• Correcting the effect of stellar spots on ARIEL transmission spectra

Cited by in corpus (4)

• TOI-4438 b: a transiting mini-Neptune amenable to atmospheric characterization
• The strange case of Na I in the atmosphere of HD209458 b: Reconciling low- and high-resolution spectroscopic observations G
• A reanalysis of the LHS 1140 b atmosphere observed with the Hubble Space Telescope
• PAStar: a model for stellar surface from the Sun to active stars