Abundant sub-micron grains revealed in newly discovered extreme debris discs

Moór, Attila and Ábrahám, Péter and Su, Kate Y L and Henning, Thomas and Marino, Sebastian and Chen, Lei and Kóspál, Ágnes and Pawellek, Nicole and Varga, József and Vida, Krisztián (2024) Abundant sub-micron grains revealed in newly discovered extreme debris discs. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 528 (3). pp. 4528-4546. ISSN 0035-8711

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Abstract

Extreme debris discs (EDDs) are bright and warm circumstellar dusty structures around main sequence stars. They may represent the outcome of giant collisions occuring in the terrestrial region between large planetesimals or planetary bodies, and thus provide a rare opportunity to peer into the aftermaths of these events. Here, we report on results of a mini-survey we conducted with the aim to increase the number of known EDDs, investigate the presence of solid-state features around 10 μm in eight EDDs, and classify them into the silica or silicate dominated groups. We identify four new EDDs and derive their fundamental properties. For these, and for four other previously known discs, we study the spectral energy distribution around 10 μm by means of VLT/VISIR photometryin three narrow-band filters and conclude that all eight objects likely exhibit solid-state emission features from sub-micron grains. We find that four discs probably belong to the silicate dominated subgroup. Considering the age distribution of the entire EDD sample, we find that their incidence begins to decrease only after 300 Myr, suggesting that the earlier common picture that these objects are related to the formation of rocky planets may not be exclusive, and that other processes may be involved for older objects (≳100 Myr). Because most of the older EDD systems have wide, eccentric companions, we suggest that binarity may play a role in triggering late giant collisions.

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