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A Coupled Analysis of Atmospheric Mass Loss and Tidal Evolution in XUV Irradiated Exoplanets: The TRAPPIST-1 Case Study

Becker, Juliette and Gallo, Elena and Hodges-Kluck, Edmund and Adams, Fred C. and Barnes, Rory (2020) A Coupled Analysis of Atmospheric Mass Loss and Tidal Evolution in XUV Irradiated Exoplanets: The TRAPPIST-1 Case Study. Astronomical Journal, 159 (6). Art. No. 275. ISSN 1538-3881. doi:10.3847/1538-3881/ab8fb0.

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Exoplanets residing close to their stars can experience evolution of both their physical structures and their orbits due to the influence of their host stars. In this work, we present a coupled analysis of dynamical tidal dissipation and atmospheric mass loss for exoplanets in X-ray and ultraviolet (XUV) irradiated environments. As our primary application, we use this model to study the TRAPPIST-1 system and place constraints on the interior structure and orbital evolution of the planets. We start by reporting on an ultraviolet continuum flux measurement (centered around ~1900 Å) for the star TRAPPIST-1, based on 300 ks of Neil Gehrels Swift Observatory data, and which enables an estimate of the XUV-driven thermal escape arising from XUV photodissociation for each planet. We find that the X-ray flaring luminosity, measured from our X-ray detections, of TRAPPIST-1 is 5.6 × 10⁻⁴ L*, while the full flux including non-flaring periods is 6.1 × 10⁻⁵ L*, when L* is TRAPPIST-1's bolometric luminosity. We then construct a model that includes both atmospheric mass loss and tidal evolution and requires the planets to attain their present-day orbital elements during this coupled evolution. We use this model to constrain the ratio Q′ = 3Q/2k₂ for each planet. Finally, we use additional numerical models implemented with the Virtual Planet Simulator VPLanet to study ocean retention for these planets using our derived system parameters.

Item Type:Article
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URLURL TypeDescription Paper ItemCode, data, and supplemental figures
Becker, Juliette0000-0002-7733-4522
Hodges-Kluck, Edmund0000-0002-2397-206X
Adams, Fred C.0000-0002-8167-1767
Additional Information:© 2020 The American Astronomical Society. Received 2019 October 1; revised 2020 April 6; accepted 2020 April 24; published 2020 May 26. We thank the referee for a useful report. We thank Sarah Peacock and Francesco Haardt for assistance. We also thank Andrew Vanderburg, Eric Agol, Konstantin Batygin, Erik Petigura, Erin May, and Beate Stelzer for useful conversations. During this work, J.C.B. has been supported by the Leinweber Center for Theoretical Physical Graduate Fellowship and the Heising-Simons 51 Pegasi b postdoctoral fellowship. R.B. acknowledges support from the NASA Astrobiology Program grant No. 80NSSC18K0829.
Funding AgencyGrant Number
Leinweber Center for Theoretical PhysicsUNSPECIFIED
Heising-Simons Foundation51 Pegasi b Fellowship
Subject Keywords:Exoplanets ; Extrasolar rocky planets ; Exoplanet atmospheres ; Exoplanet structure
Issue or Number:6
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanets (498); Extrasolar rocky planets (511); Exoplanet atmospheres (487); Exoplanet structure (495)
Record Number:CaltechAUTHORS:20200526-143420880
Persistent URL:
Official Citation:Juliette Becker et al 2020 AJ 159 275
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103469
Deposited By: Tony Diaz
Deposited On:26 May 2020 22:52
Last Modified:16 Nov 2021 18:21

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