by Dr. Matthew Templeton
While researching another project, I browsed our archive of AAVSO Abstracts, one of our publications prior to the first Journal. At the Spring 1963 Meeting, Tom Cragg presented a paper entitled "Sanctum Observers and the Minima of the Mira Stars", which discussed the observational status of Mira light curves with flat bottoms. At the time he (correctly) ascribed them to Miras with nearby companions that are brighter than the variable at minimum. Unfortunately, this talk doesn't appear in ADS so it's hard to say whether this work has been pursued since.
It caught my eye because Arne and I encountered this problem independent of Cragg's work when we looked at the lightcurve of Z Tau 3-4 years ago. Many observations of that star had been marked discrepant, when in fact they were absolutely right! Those observers were able to split the companion (about 5" away) and were able to report Z Tau alone.
What Arne and I are curious about (but have no time to investigate, honestly) is whether any of these stars have been discussed in literature beyond 1963 in the context of their multiplicity, and whether anything was known about their companions.
Is anyone interested in investigating this? It's sort of a combination literature search and lightcurve analysis. It would also be useful if you download the data *including the ones marked discrepant* and see whether any observers had split them in the past.
You can download a copy of Tom Cragg's paper by clicking here.