Warm Coronal Rain on Young Solar Analog EK Draconis?

Abstract

We report a moderate-resolution, 1290-1430 Å spectrum of young solar analog EK Draconis (HD 129333: G1.5 V), obtained by Cosmic Origins Spectrograph on Hubble Space Telescope. The 20 minute observation, remarkably, captured two distinct "flares" in the Si IV 1400 Å doublet (T ~ 6 × 10⁴ K); very broad profiles of Si IV and the C II 1335 Å multiplet (T ~ 3 × 10⁴ K); and prominent Fe XXI λ1354 coronal forbidden line emission (T ~ 10 MK). The bright Si IV features are significantly redshifted compared to the milder, although still redshifted, equivalent components of solar-twin α¹ Cen (HD 128620: G2 V). The broad, shifted, flaring hot-line profiles of EK Dra indicate not only that the subcoronal plasma of the young sun is highly dynamic, but also that the Si IV-bearing gas must be continually accreting onto the lower atmosphere, perhaps the stellar equivalent of warm "coronal rain."