https://phys.org/news/2021-12-evidence- ... dwarf.html
by Sam Sholtis, Pennsylvania State University
High-resolution spectroscopic observations of a stellar flare on a small, cool star indicate the possibility of coronal rain, a phenomenon that has been observed on our sun but not yet confirmed on a star of this size. This faint star, known as vB 10, which is about a tenth the size of the sun and produces less than 1% of the sun's energy, was studied using the Penn State Habitable-zone Planet Finder (HPF) at the large Hobby Eberly Telescope (with its 10 m mirror). These observations with the HPF spectrograph allowed researchers to measure a shift in the wavelength of certain atomic lines from the flare that are consistent with hot plasma raining back down on the star's surface and are similar to observations of coronal rain from the sun.
A paper describing the observations, by a team led by Penn State scientists, includes a time-series analysis of the flare and could help astronomers put constraints on the energy and frequency of such events. The paper has been accepted for publication in The Astrophysical Journal and is available online.
"As the name suggests, the Habitable-zone Planet Finder was designed to detect planets by looking for shifts in the light spectra from M-dwarf stars that result from the star 'wobbling' under the gravitational pull of orbiting planets," said Larry Ramsey, professor emeritus of astronomy and astrophysics at Penn State and an author of the paper. "But we knew from the start that we might learn more about stellar activity from these spectra than we do about planets."