Constraining the Physical Properties of Stellar Coronal Mass Ejections with Coronal Dimming: Application to Far-ultraviolet Data of ? Eridani

Abstract Coronal mass ejections (CMEs) are a prominent contributor to solar system space weather and might have impacted the Sun’s early angular momentum evolution. A signal diagnostic of CMEs on Sun is coronal dimming: drop in emission, tied CME, that direct result removing emitting plasma from corona. We present results dimming analysis Fe xii 1349 Å xxi 1354 emission ? Eridani ( Eri), young K2 dwarf, with archival far-ultraviolet observations by Hubble Space Telescope’s Cosmic Origins Spectrograph. Following flare 2015 February, Eri’s declined 81 ± 5%. Although enticing, scant 3.8 minutes preflare allows for possibility decline was decay an earlier, unseen flare. Dimming nondetections following each three flares constrain possible ejected -emitting (1 MK) less than few × 10 15 g. This implies ejecting this much or more 1 MK occur times per day Eri. On Sun, g once every days. For Eri, mass-loss rate due CME-ejected could be < 0.6 M ? ? , well below star’s estimated 30 (wind + CMEs). The order-of-magnitude formalism we developed these estimates can broadly applied any star.