The Mega-MUSCLES Treasury Survey

The Mega-MUSCLES Treasury Survey is a large HST, Chandra, XMM, Swift, and ground-based program that has obtained time-series observations of the energetic XUV spectra of twelve M stars. It is a follow-on to the successful MUSCLES survey, which has generated the most widely used database for early-M and K-dwarf irradiance spectra to support a wide range of atmospheric stability and biomarker modeling work. Mega-MUSCLES has extended the observations to lower mass M stars, including (a) new M dwarf exoplanet hosts with varying properties; (b) reference M dwarfs below 0.3 solar masses that may be used as proxies for M dwarf planet hosts discovered after HST’s lifetime; and (c) more rapidly rotating stars of GJ1132’s mass to probe XUV evolution over gigayear timescales. We have also gathered the first panchromatic SEDs of rocky planet hosts GJ1132 and Trappist-1. These data will inform upcoming observations of potential Earth-like planets with facilities like JWST, by determining the potential for XUV irradiation to erode a planet’s gaseous envelope and FUV/NUV-driven photochemistry to shape an atmosphere’s molecular abundances, including potential biomarkers like O2, O3, and CH4. In this presentation, we will discuss the findings from the Mega-MUSCLES observations and introduce the new SEDs available to the community as MAST High Level Science Products.