Quantifying the Effects of Host Star UV Scaling Relationships on Photochemical Modeling of Exoplanet Atmospheres
Abstract
Photochemical models are necessary to predict and interpret the primary properties of exoplanet atmospheres (e.g. chemical composition, thermal structure, and aerosol production). This type of modeling is especially critical for understanding the many cool and low-mass exoplanets that will be discovered by TESS and characterized by HST and JWST, for which chemical equilibrium is a poor assumption. The UV spectrum of the host star is a key input to photochemical models. Unfortunately most exoplanet hosts have not had their UV properties characterized, and the prevailing M dwarf hosts are known to have especially diverse UV spectra. In the absence of UV observations of individual stars, scaling relations can be used to reconstruct their approximate UV spectra as inputs into photochemical models. However, the level of uncertainty introduced by using such scaling laws has not been quantified.
With this proposal we will determine for the first time the necessary level of precision and wavelength coverage for UV observations of exoplanet host stars to be used as input to photochemical calculations. We will do this by employing existing HST spectra of exoplanet host stars to generate photochemical models of low-mass exoplanet atmospheres using the publicly available code PHOTOCHEM. We will measure the errors introduced into such models by adopting UV scaling relations and/or low-precision input spectra. As a result of this work, we will identify any critical gaps in the complement of HST UV spectra of exoplanet hosts to enable the highest impact science for low-mass exoplanets in the era of JWST and ground-based ELTs.- Publication:
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HST Proposal
- Pub Date:
- May 2020
- Bibcode:
- 2020hst..prop16135K