Abstract
Abstract We present a 5 Å–100 μm 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 Lyα–EUV relations often used to estimate the 100–911 Å 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 semiempirical, noise-free model of the stellar ultraviolet spectrum based on our observations for use in atmospheric modeling of the TRAPPIST-1 planets.
Highlights
Among the thousands of planetary systems that have been discovered over the past two and a half decades, TRAPPIST-1 is a standout case
TRAPPIST-1 is the faintest target in the Mega-MUSCLES survey, and the Spectral Energy Distribution (SED) presented here both represents the state-of-the-art for observation of the high-energy flux of low-mass stars and demonstrates the limits of our current observing facilities
Obtaining the ultraviolet spectroscopy pushed the capabilities of COS to their limits, with many expected emission lines remaining below the noise limit
Summary
Among the thousands of planetary systems that have been discovered over the past two and a half decades, TRAPPIST-1 is a standout case. Wheatley et al (2017) observed TRAPPIST-1 with XMMNewton (XMM ), finding variable X-ray luminosity with intensity similar to the modern quiescent Sun Because of their proximity to the host stars, the planets would experience XUV intensities much higher than the Earth, sufficient to significantly alter their atmospheres and strip away hydrogen from water in their atmospheres and (if present) oceans (Ribas et al 2016; Airapetian et al 2017). Peacock et al (2019) used the PHOENIX stellar atmosphere code to model the chromosphere and transition region of TRAPPIST-1, scaling it to the Bourrier et al (2017a) Lyman α measurement and to distance-adjusted GALEX observations of stars with a similar spectral type They found that the flux emitted between 100–912 ̊A varies by an order of magnitude depending on which calibrator was used. We discuss the changes made to the data processing and stellar emission modelling implemented for Mega-MUSCLES compared with MUSCLES, present a semi-empirical model for use in model atmosphere simulations, and compare the observed SED to the Peacock et al (2019) models
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
