Flare star

Flare activity among late-type stars was first reported by A. van Maanen in 1945, for WX Ursae Majoris and YZ Canis Minoris.

Additionally, nine stars similar to the Sun had also been seen to undergo flare events[2] prior to the flood of superflare data from the Kepler observatory.

It has been proposed that the mechanism for this is similar to that of the RS CVn variables in that the flares are being induced by a companion, namely an unseen Jupiter-like planet in a close orbit.

During the preflare phase, which usually lasts for a few minutes, the coronal plasmas slowly heats up to temperatures of tens of millions Kelvin.

During the impulsive phase, which lasts for three to ten minutes, a large number of electrons and sometimes also ions are accelerated to extremely high energies ranging from keV to MeV.

[8] On April 23, 2014, NASA's Swift satellite detected the strongest, hottest, and longest-lasting sequence of stellar flares ever seen from a nearby red dwarf, DG Canum Venaticorum.

[9] The Sun's nearest stellar neighbor Proxima Centauri is a flare star that undergoes occasional increases in brightness because of magnetic activity.

[10] The star's magnetic field is created by convection throughout the stellar body, and the resulting flare activity generates a total X-ray emission similar to that produced by the Sun.

[14] By comparison, the magnetic field of the Sun averages 1 G (100 μT), although it can rise as high as 3 kG (0.3 T) in active sunspot regions.

[20] Its observation by Swift suggested the presence of hard X-rays in the well-established Neupert effect as seen in solar flares.