similar event

Robin Leadbeater

Here is a similar event back in 2006 which went from mag 11.5 to mag 7.5. There were several papers on this eg this one with members of the amateur community (BAA/CBA etc)  as co-authors…677.1268G/abstract

which deduced the lensing object was likely a low mass star or brown dwarf. Their paper also suggested that it could be a a productive technique for discovering exoplanets.

(I believe my first (crude slitless) spectrum was the earliest of this object which alerted the community that this was something unusual though as far as I know that was not mentioned in any of the subsequent papers). I remember there was considerable scepticism at the time as lensing of such a bright target was considered unlikely but there have been a few more bright ones since then.