Science Seminars

Recent Observations of Stellar Flares on G-, K-, and M-dwarf Stars and Possible Mass Ejections

Speaker: Yuta Notsu (LASP)
Date: Thursday, Jan 27, 2022
Time: 4:00 PM
Location: Zoom

Seminar Abstract:

Flares are frequent energetic explosions in the stellar atmosphere, and are thought to occur by impulsive releases of magnetic energy stored around starspots. Large flares (so called “superflares”) generate strong high energy emissions and coronal mass ejections (CMEs), which can greatly affect the planetary environment and habitability. Recent Kepler/TESS photometric data have revealed the statistical properties of superflares on G, K, M-type stars.
Superflare stars are well characterized by the existence of large starspots on the surface, and their magnetic fluxes can explain well superflare energies. Flare frequency/energy depends on stellar rotation period and stellar temperature. Young rapidly-rotating stars and cooler stars tend to have frequent flares, which can be more “hazardous” for the habitable planets. However, we still do not know the emission mechanisms of superflares, and how large CMEs are associated with superflares on these active stars. Recent observational programs have detected some possible candidates of stellar CMEs (e.g., our press release last month: ), and they could be the start point for quantitatively discussing the impacts of flares and CMEs on the environment and habitability of various planets including young Earth/Mars.
In the early part of the talk, I briefly overview the recent statistical results of superflares from Kepler/TESS data. Then in the latter part, I discuss the results of recent multi-wavelength campaign observations of superflares, and discuss possible detections of mass ejections (stellar CMEs).