When “Boring” Stars Flare: The Ultraviolet Activity of GJ 887, a Bright M Star Hosting Newly Discovered Planets* | CU Experts

Abstract; GJ 887 has been spotlighted for the apparently gentle space environment it provides to its recently discovered planets. In 27 days of optical monitoring by the Transiting Exoplanet Survey Satellite (TESS), the star exhibited no detectable flares. Ultraviolet observations reveal a different story. Two high-contrast flares occurred in just 2.8 hr of far-ultraviolet monitoring by the Hubble Space Telescope. Solar scalings indicate these flares were X-class or larger events, generally associated with coronal mass ejections on the Sun. Hundreds of events of equal or greater energy likely occurred during the TESS monitoring, but produced optical contrasts too small to be detected. Strong yet optically undetectable ultraviolet flares like these could dominate the high energy emission of all M stars throughout their lives, impacting the photochemistry and erosion of atmospheres on orbiting planets.

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