AAVSO: American Association of Variable Star Observers

Flare Stars: A Short Review (Abstract)

Volume 47 number 2 (2019)

Krstinja Dzombeta
Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4, Canada; krstinja.dzombeta@mail.utoronto.ca
John R. Percy
Department of Astronomy and Astrophysics, and Dunlap Institute of Astronomy and Astrophysics, University of Toronto, Toronto ON M5S 3H4, Canada; percy@astro.utoronto.ca

Abstract

(Abstract only) We present a short review of flare stars. Flare stars, or UV Ceti stars, are a type of eruptive variable star, defined by their flaring behavior—a rapid (minutes) increase in brightness, followed by a slower (hours) decrease. This short review outlines current knowledge about flare stars, their importance, recent research developments, future research directions, and some practical activities for skilled amateur astronomers and students. Over the past decade, flare stars have been the subject of intensive research, as a result of an abundance of new data, especially from the Kepler and TESS space telescopes. The large statistical samples of data have clarified the relation between flaring and stellar spectral type, luminosity, and rotation. They have allowed for the expansion of the range of spectral types of flare stars, from K and M type dwarfs, to F and G, and possibly even A. They have confirmed the greater frequency of flares on M dwarfs, compared to K, and that flare stars’ energies follow a decreasing power law fit for the number of high-energy flares, although a break in the relationship has also been demonstrated. Current problems in flare-star research include improved modelling of the new observational results, using the dynamo theory which produces the stars’ magnetic field. What is the difference, if any, between the dynamo in completely-convective stars such as M dwarfs, and in stars such as the sun with only partial convective zones? Authors’ Note: This short review was prepared by author Krstinja Dzombeta, as a senior thesis for the Astronomy Major program at the University of Toronto, under the supervision of author John Percy, who has also revised and edited it. The full review is permanently archived at the University of Toronto Library, at: http://hdl.handle.net/1807/97060