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Published June 20, 2016 | Submitted + Published
Journal Article Open

The MUSCLES Treasury Survey III: X-ray to Infrared Spectra of 11 M and K Stars Hosting Planets

Abstract

We present a catalog of panchromatic spectral energy distributions (SEDs) for 7 M and 4 K dwarf stars that span X-ray to infrared wavelengths (5 Å –5.5 μm). These SEDs are composites of Chandra or XMM-Newton data from 5–~50 Å, a plasma emission model from ~50–100 Å, broadband empirical estimates from 100–1170 Å, Hubble Space Telescope data from 1170–5700 Å, including a reconstruction of stellar Lyα emission at 1215.67 Å, and a PHOENIX model spectrum from 5700–55000 Å. Using these SEDs, we computed the photodissociation rates of several molecules prevalent in planetary atmospheres when exposed to each star's unattenuated flux ("unshielded" photodissociation rates) and found that rates differ among stars by over an order of magnitude for most molecules. In general, the same spectral regions drive unshielded photodissociations both for the minimally and maximally FUV active stars. However, for O3 visible flux drives dissociation for the M stars whereas near-UV flux drives dissociation for the K stars. We also searched for an far-UV continuum in the assembled SEDs and detected it in 5/11 stars, where it contributes around 10% of the flux in the range spanned by the continuum bands. An ultraviolet continuum shape is resolved for the star Є Eri that shows an edge likely attributable to Si ii recombination. The 11 SEDs presented in this paper, available online through the Mikulski Archive for Space Telescopes, will be valuable for vetting stellar upper-atmosphere emission models and simulating photochemistry in exoplanet atmospheres.

Additional Information

© 2016 The American Astronomical Society. Received 2016 January 28; accepted 2016 April 12; published 2016 June 20. The data presented here were obtained as part of the HST Guest Observing programs #12464 and #13650 as well as the COS Science Team Guaranteed Time programs #12034 and #12035. This work was supported by NASA grants HST-GO-12464.01 and HST-GO-13650.01 to the University of Colorado at Boulder. We thank Tom Woods and Chris Moore for useful discussions that provided a solar context to the work. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. S.R. would like to acknowledge support from the Simons Foundation (339489, Rugheimer). F.T. is supported by the National Natural Science Foundation of China (41175039) and the Startup Fund of the Ministry of Education of China (20131029170). This work was partially supported by Chandra grants GO4-15014X and GO5-16155X from Smithsonian Astrophysical Observatory and NASA XMM grant NNX16AC09G.

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Published - apj_824_2_102.pdf

Submitted - 1604.04776v1.pdf

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August 22, 2023
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