paper

Optical and UV observations of a strong flare in the young, single K2-dwarf LQ Hya

arXiv:astro-ph/9811452 · doi:10.1046/j.1365-8711.1999.02373.x

Abstract

We present high resolution optical echelle spectra and IUE observations during a strong flare on 1993 December 22 in the very active, young, rapidly rotating, single K2 dwarf LQ Hya. The initial impulsive phase of the flare, which started sometime between 2:42 UT and 4:07 UT, was characterized by strong optical continuum enhancement and blue-shifted emission lines with broad wings. The optical chromospheric lines reached their maximum intensity at 5:31 UT, by which time the blue-shift vanished and the optical continuum enhancement had sharply decreased. Thereafter, the line emission slowly decreased and the lines red-shift in a gradual phase that lasted at least two more hours. The Mg II lines behaved similarly. Quiescent C IV flux levels were not recovered until 21 hours later, though a data gap and a possible second flare make the interpretation uncertain. In addition to the typically flare-enhanced emission lines (e.g., H_alpha and H_beta), we observe He I D_3 going into emission, plus excess emission (after subtraction of the quiescent spectrum) in other He I and several strong neutral metal lines (e.g., Mg I b). Flare enhancement of the far UV continuum generally agrees with a Si I recombination model. We estimate the total flare energy, and discuss the broad components, asymmetries, and Doppler shifts seen in some of the emission lines.

Latex file with 14 pages, 10 figures tar'ed gzip'ed. Full postscript (text and figures) available at http://www.ucm.es/info/Astrof/pub_dmg.html To be published in MNRAS

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