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arXiv · 1010.0452

An A star on an M star during a flare within a flare

Adam F. Kowalski·Suzanne L. Hawley·Jon A. Holtzman·John P. Wisniewski·Eric J. Hilton
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Abstract

M dwarfs produce explosive flare emission in the near-UV and optical continuum, and the mechanism responsible for this phenomenon is not well-understood. We present a near-UV/optical flare spectrum from the rise phase of a secondary flare, which occurred during the decay of a much larger flare. The newly formed flare emission resembles the spectrum of an early-type star, with the Balmer lines and continuum in absorption. We model this observation phenomonologically as a temperature bump (hot spot) near the photosphere of the M dwarf. The amount of heating implied by our model (ΔT_phot ~ 16,000K) is far more than predicted by chromospheric backwarming in current 1D RHD flare models (ΔT_phot ~ 1200K).

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Adam F. Kowalski, Suzanne L. Hawley, Jon A. Holtzman, John P. Wisniewski, Eric J. Hilton. 2010-10-03. An A star on an M star during a flare within a flare. https://doi.org/10.1017/s1743921311015341

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