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While trying to see color changes in the variable hypergiant HD 97671, I found something weird with the Tycho catalogue. I know that the published mean B-V colors may be wrong because they are oftenly a result of differences between Bt and Vt mag for stars that vary too much (mira stars oftenly show B-V around 1.0 published!!) But for this very red star (B-V 2.5) I don't know where the published values come from: The published color seems more or less right (Bt-Vt 2.6) but when you get individual observations from the Tycho-Epoch there is no such red magnitudes since the Bt is not 11.69 as stated in the catalogue but something around 10.5 ! (Bt-Vt is generally ~1.5!) Obviously the red color published is okay but it's not derived from the source photometry! I don't understand! What happens? Sebastian.
Return to the Powerful Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
