Sarah J. Schmidt, Adam F. Kowalski, Suzanne L. Hawley, Eric J. Hilton, John P. Wisniewski, Benjamin M. Tofflemire
We present the results of a campaign to monitor active M dwarfs using
infrared spectroscopy, supplemented with optical photometry and spectroscopy.
We detected 16 flares during nearly 50 hours of observations on EV Lac, AD Leo,
YZ CMi, and VB8. The three most energetic flares also showed infrared emission,
including the first reported detections of P\beta, P\gamma, He I 10830\AA and
Br\gamma during an M dwarf flare. The strongest flare (\Delta u = 4.02 on EV
Lac) showed emission from H\gamma, H\delta, He I 4471\AA, and Ca II K in the
UV/blue and P\beta, P\gamma, P\delta, Br\gamma, and He I 10830\AA in the
infrared. The weaker flares (\Delta u = 1.68 on EV Lac and \Delta U = 1.38 on
YZ CMi) were only observed with photometry and infrared spectroscopy; both
showed emission from P\beta, P\gamma, and He I 10830\AA. The strongest infrared
emission line, P\beta, occurred in the active mid-M dwarfs with a duty cycle of
~3-4%. To examine the most energetic flare, we used the static NLTE radiative
transfer code RH to produce model spectra based on a suite of one-dimensional
model atmospheres. Using a hotter chromosphere than previous one-dimensional
atmospheric models, we obtain line ratios that match most of the observed
emission lines.
View original:
http://arxiv.org/abs/1111.7072
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