I found it interesting that Wallerstein wrote that it was not known with certainty if RS Oph was a double star. Today, conventional thought is that recurrent novae are due to a main-sequence star losing mass, mostly hydrogen, to a white-dwarf companion. It accretes on the surface until a critical temperature is reached, at which time nuclear detonation occurs in a runaway reaction. The accreted material is blown-away into an expanding shell around the white dwarf, and the cycle begins again. This is also the cause of some planetary nebulae. Thanks for digging up that paper, Kurt.
From: Canopus56 <canopus56@yahoo.com> Read Wallerstein's 1958 paper on the violet color during the 1958 eruption:
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