HAZMAT. I. THE EVOLUTION OF FAR-UV AND NEAR-UV EMISSION FROM EARLY M STARS

By E. Shkolnik, Travis S. Barman. 2014

149 citations recorded by the source corpus.

The spectral energy distribution, variability, and evolution of the high-energy radiation from an M dwarf planet host is crucial in understanding the planet's atmospheric evolution and habitability and in interpreting the planet's spectrum. The star's extreme-UV (EUV), far-UV (FUV), and near-UV (NUV) emission can chemically modify, ionize, and erode the atmosphere over time. This makes determining the lifetime exposure of such planets to stellar UV radiation critical for both the evolution of a planet's atmosphere and our potential to characterize it. Using the early M star members of nearby young moving groups, which sample critical ages in planet formation and evolution, we measure the evolution of the GALEX NUV and FUV flux as a function of age. The median UV flux remains at a “saturated” level for a few hundred million years, analogous to that observed for X-ray emission. By the age of the Hyades Cluster (650 Myr), we measure a drop in UV flux by a factor of 2–3 followed by a steep drop from old (several Gyrs) field stars. This decline in activity beyond 300 Myr follows roughly t−1. Despite this clear evolution, there remains a wide range, of 1–2 orders of magnitude, in observed emission levels at every age. These UV data supply the much-needed constraints to M dwarf upper-atmosphere models, which will provide empirically motivated EUV predictions and more accurate age-dependent UV spectra as inputs to planetary photochemical models.

Subfields: Astronomy and Astrophysics, Education

View Paper: https://www.semanticscholar.org/paper/91a98c0525bc17486b1d0751ed7e46dfbbb45784

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Citations in the corpus

The Surface UV Environment on Planets Orbiting M Dwarfs: Implications for Prebiotic Chemistry and the Need for Experimental Follow-up (2017, background): “Young M dwarfs, especially pre-main-sequence Mdwarfs, emit a larger fraction of their bolometric luminosity as NUV radiation thanintheir main-sequence phase (Shkolnik & Barman 2014).”
THE KEPLER CATALOG OF STELLAR FLARES (2016, background): “Ultraviolet excess emission appears to follow X-ray luminosity for young stars, with a similar saturation regime (Shkolnik & Barman 2014).”
THE MUSCLES TREASURY SURVEY. I. MOTIVATION AND OVERVIEW (2016, methodology): “While the long-term evolution of the broadband UV luminosity function of M dwarfs can be constrained with large photometric samples from GALEX (e.g., Shkolnik & Barman 2014), a further uncertainty in the temporal behavior of low-mass exoplanet host stars is the variability on time scales of years…”