ASASSN-24fw, monitored by the All-Sky Automated Survey for SuperNovae, underwent a rapid and deep dimming event beginning in late 2024 and lasting until 2025 June. The pre-dimming spectral energy distribution indicates that ASASSN-24fw is an F-type main-sequence star with a persistent infrared excess, corresponding to a fractional luminosity of about 10 per cent.
While long-duration stellar dimming events have become increasingly common in recent years, ASASSN-24fw is distinguished by a pronounced flat-bottomed light curve lasting nearly 200 d. International team of astronomers, led by Sarang Shah (former post-doc at the Copernicus Center in Warsaw), and including Gergely Hajdu and Bogumił Pilecki from CAMK PAN, Warsaw, analysed this event using available photometric and spectroscopic data obtained during the dimming phase.
The results are published in Monthly Notices of the Royal Astronomical Society in paper The nature of ASASSN-24fw’s occultation: modelling the event as dimming by optically thick rings around a substellar companion (MNRAS, vol. 546, Issue 3 March 2026).
Royal Astronomical Society press release.
Picture credit: S. Shah et al.
