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

D Montes, SH Saar, Andrew Collier Cameron, YC Unruh

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43 Citations (Scopus)

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 approximate to 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.

Original languageEnglish
Pages (from-to)pp.45-60.
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume305
Issue number1
Publication statusPublished - 1 May 1999

Keywords

  • line : profiles
  • stars : activity
  • stars : chromospheres
  • stars : flare
  • stars : individual : LQ Hya
  • stars : late-type
  • CHROMOSPHERICALLY ACTIVE BINARIES
  • H-ALPHA EMISSION
  • CA-II-H
  • RS CANUM VENATICORUM
  • YZ-CANIS-MINORIS
  • X-RAY FLARE
  • SOLAR-FLARES
  • UV CETI
  • ROTATIONAL MODULATION
  • CLOSE BINARIES

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