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


The UV light curve (with a waveband centered at 1928 Angstroms and a full width at half max of 657 Angstroms) constructed using SWIFT UVOT observations taken with the uvw2 filter. The single detection is plotted as a red point with error bars, and upper limits are plotted as grey points with error arrows extending downwards. The average flux over the full 300ks of observations is plotted as an orange line, with the derived 1σ uncertainty plotted as a filled orange background region. We note that the average flux was derived from the stacked 300ks image, rather than from the points plotted here. The data used to plot this lightcurve is also given in Table 1.

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 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 a UV continuum flux measurement (centered around ∼ 1900 Angstroms) 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 photo-dissociation for each planet.

We find that the X-ray flaring luminosity, measured from our X-ray detections, of TRAPPIST-1 is 5.6 ×10−4L∗, while the full flux including nonflaring periods is 6.1 ×10−5L∗, 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 Q0 = 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.

Juliette Becker, Elena Gallo, Edmund Hodges-Kluck, Fred C. Adams, Rory Barnes
Comments: accepted to AJ. See extra figures, data, and scripts at this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2005.01740 [astro-ph.EP] or arXiv:2005.01740v1 [astro-ph.EP] for this version)
Submission history
From: Juliette Becker
[v1] Mon, 4 May 2020 18:00:05 UTC (300 KB)
https://arxiv.org/abs/2005.01740
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