0 Assigned ID: 179 ----- Attempting Submission 1 (Wed Mar 04 20:46:16 GMT 2020) ----- HST Phase I Proposal 179 successfully submitted. Receipt: # 179-1 ----- Attempting Submission 2 (Fri Mar 06 22:08:07 GMT 2020) ----- HST Phase I Proposal 179 successfully submitted. Receipt: # 179-2 ----- Attempting Submission 3 (Fri Mar 06 22:54:34 GMT 2020) ----- 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. Our team consists of experts in the field in photochemical modeling, exoplanet radiative transfer modeling, and UV spectroscopy. The PI, Eliza Kempton, is an atmospheric theorist who has co-authored more than 40 papers on the subject of exoplanet atmospheres, including prominent first author papers on exoplanet radiative transfer, transmission spectroscopy, and photochemistry. She has been a theorist co-I on 11 HST GO, AR, and DDT programs since 2010, totaling 245 orbits. Co-Is Shawn Domagal-Goldman and Giada Arney are experts in the modeling of terrestrial exoplanets, including their photochemistry. Both are extensive users and developers of the ATMOS code and the PHOTOCHEM module that will be used in this work. Co-I Allison Youngblood is a member of the HST MUSCLES Treasury Survey team and is the first author of papers II and IV in the MUSCLES publication series involving Ly-alpha emission and UV scaling relationships for M stars. She is the PI of 3 recent HST GO proposals and 1 AR proposal, and a co-I on many, including the Mega-MUSCLES program. Co-I Teal is a graduate student at the University of Maryland who has 3+ years of experience working with the ATMOS and PHOTOCHEM codes and who will undertake the modeling work described in this proposal as the first part of their PhD thesis. PI Kempton will lead the team and will supervise graduate student co-I Teal, who will perform the majority of the modeling work laid out in this proposal. Co-Is Arney and Domagal-Goldman will provide input on the use of ATMOS and PHOTOCHEM and on general issues related to modeling Earth-like exoplanets. Co-I Youngblood will provide input on UV observations of exoplanet host stars with HST, including how to best incorporate previous HST observations into the modeling efforts described in this proposal. Exoplanets and Exoplanet Formation 0 Regular false false true true false SUPPORTED