We calculate that the baseline atmospheric mass-loss rate for AU Mic b is ∼10 8 g s −1, although this rate can be as high as ∼10 14 g s −1 during flares with erg s −1. There is a 100 × increase in flux at continuum wavelengths λ < 1100 Å in each flare, which may be caused by thermal Bremsstrahlung emission. The majority of the energy in each of these flares is released from the transition region between the chromosphere and the corona. We detect 13 flares in the FUV white-light curve with energies ranging from 10 29 to 10 31 erg s. We provide an itemization of 120 emission features in the HST/COS FUV spectrum and quantify the flux contributions from formation temperatures ranging from 10 4 to 10 7 K.
In this paper, we present over 5 hr of far-UV (FUV) observations of AU Mic taken with the Cosmic Origins Spectrograph (COS 1070-1360 Å) on the Hubble Space Telescope (HST).
Therefore, this system provides a unique opportunity to quantify the effects of stellar X-ray and UV irradiation on planetary atmospheres as a function of both age and orbital separation. The active ∼22 Myr M dwarf AU Mic hosts two exoplanets orbiting interior to its debris disk. High-energy X-ray and ultraviolet (UV) radiation from young stars impacts planetary atmospheric chemistry and mass loss. Lyngby, Denmarkĭepartment of Physics and Astronomy, Dartmouth College, Hanover, NH 03755, USAĭepartment of Astronomy, University of California at Berkeley, CA 94720-3411, USAĭepartment of Physics and Astronomy, George Mason University, Fairfax, VA, USAĮarth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road, NW, Washington, DC 20015, USAĭepartment of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095, USA National Space Institute, Technical University of Denmark, Elektrovej 328, DK-2800 Kgs. NASA Goddard Space Flight Center, Greenbelt, MD 20771, USAĭepartment of Astronomy, University of Maryland, College Park, MD 20742, USAĭepartment of the Geophysical Sciences, University of Chicago, Chicago, IL 60637, USAĭepartment of Earth Sciences, University of Hawaií at Manoa, Honolulu, HI 96822, USA Ellis Avenue, Chicago, IL 60637, USA for Atmospheric and Space Physics, University of Colorado, 600 UCB, Boulder, CO 80309, USAĭepartment of Astrophysical and Planetary Sciences, University of Colorado, UCB 389, Boulder, CO 80309, USAĬenter for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309, USA Department of Astronomy and Astrophysics, University of Chicago, 5640 S.
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