2015/08/02 by M. M. Katsova, M. A. Livshits · 2 citations
Physics and Astronomy · #astro-ph.SR
paper · pdf · doi:10.1007/s11207-015-0752-6
21 pages, 4 figures
arxiv created 2015/08/02 · arxiv updated 2015/08/19
We analyze new observations of superflares on G-stars discovered in the optical and near IR ranges with the Kepler mission. An evolution of solar-type activity is discussed. We give an estimate of the maximal total energy, Etot = 1034 erg of a flare that can occur on the young Sun at its age of 1 Gyr when the cycle was formed. We believe that the main source of the flare optical continuum is a low-temperature condensation forming in the course of the response of the chromosphere to an impulsive heating. For a superflare on the young Sun, we adopt the accelerated electron flux, Fe (E>20 keV) = 3 × 1011 erg cm-2 s-1, that is limited by the return current, and obtain the area of the optical continuum source on a G star, S ≈ 1019 cm2. This value is close to the area of the Hα-ribbons in the largest solar flares, while the area of bright patches of a white-light flare on the contemporary Sun is smaller by about two orders of magnitude. At the same electron flux and the hard electron spectrum, the stellar flare of the similar energy should be accompanied by the microwave source of about 2 mJy at frequencies 10--100 GHz at distance 100 pc. We discuss the possible detection of the flare-produced lithium in the course of spallation reactions. The detection of the flare microwave source and the emission in the Li resonant line could demonstrate how effective can be particle acceleration on stars in the lower part of the main sequence.