Effect of UV Radiation on the Spectral Fingerprints of Earth-like Planets Orbiting M dwarfs

S. Rugheimer; L. Kaltenegger; A. Segura; J. Linsky; S. Mohanty

doi:10.1088/0004-637X/809/1/57

paper

Effect of UV Radiation on the Spectral Fingerprints of Earth-like Planets Orbiting M dwarfs

arXiv:1506.07202 · doi:10.1088/0004-637X/809/1/57

Abstract

We model the atmospheres and spectra of Earth-like planets orbiting the entire grid of M dwarfs for active and inactive stellar models with $T_{e f f}$ = 2300K to $T_{e f f}$ = 3800K and for six observed MUSCLES M dwarfs with UV radiation data. We set the Earth-like planets at the 1AU equivalent distance and show spectra from the VIS to IR (0.4 $μ$ m - 20 $μ$ m) to compare detectability of features in different wavelength ranges with JWST and other future ground- and spaced-based missions to characterize exo-Earths. We focus on the effect of UV activity levels on detectable atmospheric features that indicate habitability on Earth, namely: H $_{2}$ O, O $_{3}$ , CH $_{4}$ , N $_{2}$ O and CH $_{3}$ Cl. To observe signatures of life - O $_{2}$ /O $_{3}$ in combination with reducing species like CH $_{4}$ , we find that early and active M dwarfs are the best targets of the M star grid for future telescopes. The O $_{2}$ spectral feature at 0.76 $μ$ m is increasingly difficult to detect in reflected light of later M dwarfs due to low stellar flux in that wavelength region. N $_{2}$ O, another biosignature detectable in the IR, builds up to observable concentrations in our planetary models around M dwarfs with low UV flux. CH $_{3}$ Cl could become detectable, depending on the depth of the overlapping N $_{2}$ O feature. We present a spectral database of Earth-like planets around cool stars for directly imaged planets as a framework for interpreting future lightcurves, direct imaging, and secondary eclipse measurements of the atmospheres of terrestrial planets in the HZ to design and assess future telescope capabilities.

in press, ApJ (submitted August 18, 2014), 16 pages, 12 figures

Effect of UV Radiation on the Spectral Fingerprints of Earth-like Planets Orbiting M dwarfs

Abstract

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