In February this year we informed you about the historic first localization of the position of a flare relative to spots on a star other than the Sun, made by employees of our Department. Today we are pleased to inform that our new paper has just been published, in which we show that during this flare, magnetic loops, partially filled with matter, gradually floated over the area of the spots: Analysis of the Stellar Occultations during the Unprecedented Long-duration Flare, K. Bicz, R. Falewicz, P. Heinzel3, M. Pietras, and P. Preś, The Astrophysical Journal Letters, 972, L11.

Obtaining this result was possible through incredibly precise measurements of brightness provided by the TESS mission. After correcting shifts in the star’s brightness, stemming from the effect of spotting, we have managed to retrieve a clear light curve of the flare itself, as mentioned earlier. On this curve we noticed a few brief darkenings that appeared nearly exactly every rotation cycle of the star. This is a strong indication that, at the time, there was a cloud of matter in the star’s outer atmosphere, rotating along with it, that with each rotation obscured the bright area of the flare. We have attempted to model the location of this cloud and its physical properties. The results proved to be consistent and suggest that a quite dense cloud of matter, most likely magnetically linked with the spot itself, was slowly floating over the area of spots and the flare.

The behaviour of this structure can be seen in the attached animation. We can infer about the location and properties of the cloud only when it covers the area of the flare, hence its changes are presented as spikes. The cloud is marked with a darker colour, while its brighter (transparent) part depicts our suggested course of the magnetic field in which it was located. The behaviour and properties of this structure resemble cool flare loops observed on the Sun or a quiet protuberance in the early stages of activation.

It is remarkable to us that such a detailed unfolding of the location of three different phenomena was possible when observing a star that we see in a telescope only as a single point. As mentioned earlier, it was made possible through very precise measurement of brightness made by the TESS mission. A combination of two features of our star also played a role: its very fast rotation and the extremely long-lasting flare visible in white light.