The Mega-MUSCLES Spectral Energy Distribution Of TRAPPIST-1

TL;DR

This paper provides a comprehensive spectral energy distribution of TRAPPIST-1 across a wide wavelength range, combining observations and models to improve understanding of its ultraviolet to X-ray emission for planetary atmosphere studies.

Contribution

It introduces a new Differential Emission Measure model for the unobserved EUV spectrum and offers a semi-empirical UV spectrum model for exoplanet atmospheric modeling.

Findings

Enhanced EUV spectrum estimation with the new DEM model.

A noise-free semi-empirical UV spectrum for TRAPPIST-1.

Comprehensive SED covering 5A-100um for the star.

Abstract

We present a 5A-100um Spectral Energy Distribution (SED) of the ultracool dwarf star TRAPPIST-1, obtained as part of the Mega-MUSCLES Treasury Survey. The SED combines ultraviolet and blue-optical spectroscopy obtained with the Hubble Space Telescope, X-ray spectroscopy obtained with XMM-Newton, and models of the stellar photosphere, chromosphere, transition region and corona. A new Differential Emission Measure model of the unobserved extreme-ultraviolet spectrum is provided, improving on the Lyman alpha to EUV relations often used to estimate the 100-911A flux from low-mass stars. We describe the observations and models used, as well as the recipe for combining them into an SED. We also provide a semi-empirical, noise-free model of the stellar ultraviolet spectrum based on our observations for use in atmospheric modelling of the TRAPPIST-1 planets.