Extreme-Ultraviolet Flares in an F2 Star

Abstract

We report on the coronal properties of two early F dwarfs. For both stars, spectroscopic data reveal a hot corona with material at temperatures as high as 10^7.1-10^7.2 K. The EUV photometric observations of one of the stars (HR 120: F2) reveal two large flares with rapid decay times. The rapid decays are in striking contrast with previously published slowly decaying flares on a late type F star (HR 1817: F8/9). Analysis of decay times suggests that the loop sizes which flared in the F2 star are significantly shorter than those which flared in the F8/9 star. We discuss these results in the context of a proposal made by Giampapa & Rosner.