Superflares and Variability in Solar-Type Stars with $\it TESS$ in the Southern Hemisphere

Lauren Doyle, Gavin Ramsay, J. Gerard Doyle

Published 2020-03-31Version 1

Superflares on solar-type stars has been a rapidly developing field ever since the launch of $\it Kepler$. Over the years, there have been several studies investigating the statistics of these explosive events. In this study, we present a statistical analysis of stellar flares on solar-type stars made using photometric data in 2-min cadence from $\it TESS$ of the whole southern hemisphere (sectors 1 - 13). We derive rotational periods for all stars in our sample from rotational modulations present in the lightcurve as a result of large starspot(s) on the surface. We identify 1980 stellar flares from 209 solar-type stars with energies in the range of $10^{31} - 10^{36}$erg (using the solar flare classification, this corresponds to X1 - X100,000) and conduct an analysis into their properties. We investigate the rotational phase of the flares and find no preference for any phase suggesting the flares are randomly distributed. As a benchmark, we use GOES data of solar flares to detail the close relationship between solar flares and sunspots. In addition, we also calculate approximate spot areas for each of our stars and compare this to flare number, rotational phase, and flare energy. Additionally, two of our stars were observed in the continuous viewing zone with lightcurves spanning one year, as a result, we examine the stellar variability of these stars in more detail.