Optical and ultraviolet observations of a strong flare in the young, single K2 dwarf LQ Hya
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 blueshifted emission lines with broad wings. The optical chromospheric lines reached their maximum intensity at ~ 5:31 ut, by which time the blueshift vanished and the optical continuum enhancement had sharply decreased. Thereafter, the line emission slowly decreased and the lines redshift 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 h 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-ultraviolet continuum generally agrees with an 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 1999
- DOI:
- 10.1046/j.1365-8711.1999.02373.x
- arXiv:
- arXiv:astro-ph/9811452
- Bibcode:
- 1999MNRAS.305...45M
- Keywords:
-
- LINE: PROFILES;
- STARS: ACTIVITY;
- STARS: CHROMOSPHERES;
- STARS: FLARE;
- STARS: INDIVIDUAL: LQ HYA;
- STARS: LATE-TYPE;
- Astrophysics
- E-Print:
- 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