Kavli Affiliate: Gregory Herczeg
| First 5 Authors: Laura Flagg, Christopher Johns-Krull, Kevin France, Gregory Herczeg, Joan Najita
| Summary:
Molecular hydrogen is the most abundant molecule in the Galaxy and plays
important roles for planets, their circumstellar environments, and many of
their host stars. We have confirmed the presence of molecular hydrogen in the
AU Mic system using high-resolution FUV spectra from HST-STIS during both
quiescence and a flare. AU Mic is a $sim$23 Myr M dwarf which hosts a debris
disk and at least two planets. We estimate the temperature of the gas at 1000
to 2000 K, consistent with previous detections. Based on the radial velocities
and widths of the H$_2$ line profiles and the response of the H$_2$ lines to a
stellar flare, the H$_2$ line emission is likely produced in the star, rather
than in the disk or the planet. However, the temperature of this gas is
significantly below the temperature of the photosphere ($sim$3650 K) and the
predicted temperature of its star spots ($gtrsim$2650 K). We discuss the
possibility of colder star spots or a cold layer in the photosphere of a
pre-main sequence M dwarf.
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