Superflare UV flashes impact on Kepler-96 system: a glimpse of habitability when the ozone layer first formed on Earth [EPA]

Kepler-96 is an active solar-type star harbouring a Super-Earth planet in close orbit. Its age of 2.3 Gyr is the same as the Sun when there was a considerable increase of oxygen in Earth’s atmosphere due to micro-organisms living under the sea. We present the analysis of superflares seen on the transit lightcurves of Kepler-96b. The model used here simulates the planetary transit in a flaring star. By fitting the observational data with this model, it is possible to infer the physical properties of the flares, such as their duration and the energy released. We found 3 flares within the energy range of superflares, where the biggest superflare observed was found to have an energy of 1.81$\times$10$^{35}$ ergs. The goal is to analyse the biological impact of these superflares on the close by planet and also on a hypothetical Earth assuming the planets have protection via various atmospheres scenarios: an Archean atmosphere and Present-day atmospheres with and without oxygen. Also, we verify the attenuation of the UV radiation produced by the flares through an Archean ocean. The conclusion is that only extremophile life could survive on the surface of Kepler-96b, and if there was an ozone layer present on the planet atmosphere. However, under the Archean conditions lifeforms as \textit{E. Coli} could support the effects of the strongest superflare in this planet if it was at a depth of 48m below the ocean surface. For a hypothetical Earth, depending on the superflare size and on the resistance of the micro-organism, life could be sustained in the surface even in an Archean atmosphere or in an 8-20m ocean depth.

Read this paper on arXiv…

R. Estrela and A. Valio
Mon, 21 Aug 17

Comments: 12 pages, 8 figures, under review at Astrobiology