Detection of a Strong Stellar Flare from EUVE J1438−432

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Abstract
We present extreme-ultraviolet (EUV) observations of a strong flare from EUVE J1438-432, a source serendipitously detected with the Extreme Ultraviolet Explorer (EUVE) Right Angle Program. The flare was detected in the Lexan/boron (100 Å) band and showed a 16-fold increase over quiescent emission with a rise time of ~10 ks and a decay time of ~40 ks. Optical spectroscopy of objects within the EUVE pointing uncertainty circle revealed a pair of late-type stars (WT 486 and WT 487) both showing Balmer series in emission; either star is a good candidate for production of the flare. The peak luminosity of the flare is 5.7 × 1029 ergs s-1 with a total energy of ~5 × 1033 ergs. The flare energetics are about 2 orders of magnitude lower than the large EUV flare detected from AU Mic in 1992, but similar to other EUV-detected flares from late-type stars.