Forecasting the Impact of Stellar Activity on Transiting Exoplanet Spectra

Abstract

Exoplanet host star activity, in the form of unocculted star spots or faculae, alters the observed transmission and emission spectra of the exoplanet. This effect can be exacerbated when combining data from different epochs if the stellar photosphere varies between observations due to activity. redHere we present a method to characterize and correct for relative changes due to stellar activity by exploiting multi-epoch ($\ge$2 visits/transits) observations to place them in a consistent reference frame. Using measurements from portions of the planet's orbit where negligible planet transmission or emission can be assumed, we determine changes to the stellar spectral amplitude. With the analytical methods described here, we predict the impact of stellar variability on transit observations. Supplementing these forecasts with Kepler-measured stellar variabilities for F-, G-, K-, and M-dwarfs, and predicted transit precisions by JWST's NIRISS, NIRCam, and MIRI, we conclude that stellar activity does not impact infrared transiting exoplanet observations of most presently-known or predicted TESS targets by current or near-future platforms, such as JWST.

ApJ accepted; updated to address referee's comments; 17 pages including references, 4 figures; comments welcome

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Cited by in corpus (6)

• The Transit Light Source Effect II: The Impact of Stellar Heterogeneity on Transmission Spectra of Planets Orbiting Broadly Sun-like Stars
• Detectability of atmospheric features of Earth-like planets in the habitable zone around M dwarfs
• Investigating the physical properties of transiting hot Jupiters with the 1.5-m Kuiper Telescope
• The Influence of Stellar Contamination on the Interpretation of Near Infrared Transmission Spectra of Sub-Neptune Worlds around M-Dwarfs
• Hubble PanCET: An isothermal day-side atmosphere for the bloated gas-giant HAT-P-32Ab
• A dayside thermal inversion in the atmosphere of WASP-19b