Study of a Non-Solar Star Flare

Abstract

Violent eruptions on the surfaces of stars, flares are among the most energetic stellar phenomena. They can last anywhere from a few minutes to a few hours, and can emit radiation from long-wavelength radio waves to gamma rays. Streams of high-energy particles, some with velocities as great as one-third the speed of light, also result. Most stars appear to flare at least to some degree. Flares on our own sun, for example, are notorious for interfering with our radio signals. Because of the sun's proximity, it is relatively easy to get data on solar flares. But what about studying flares on other stars? It turns out that the best flares are observed on the M dwarfs-small, cool, reddish stars on the lower end of the main sequence. Because they lend themselves so well to flare observation, such stars are often referred to simply as "flare stars." For one thing, the faintness o fM dwarfs makes the brightening due to a flare readily detectable. It would be hard to see flares at interstellar distances on another moderately bright G-type star like the sun. On an M dwarf: however, a flare with the energy of a large solar flare could cause a twofold increase in brightness. Additionally, certain structural characteristics of M dwarfs may promote especially intense flare activity. After obtaining some background information on stellar structure and activity, we will investigate these characteristics by contrasting M dwarfs with the sun, a star about which we know much more. The remainder of this paper will present data from a recent flare on AD Leo, an M dwarf star, and discuss plans for future investigation.