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STF450 companion variable?

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#26 WRAK

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Posted 21 January 2014 - 05:27 PM

Frank, thanks for the effort you invested here - I am not sure how to read all these numbers but I tend to the interpretation that the STF450 companion is fainter than WDS advertised +9.1mag.
Wilfried

#27 freestar8n

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Posted 21 January 2014 - 06:41 PM

I'm mainly pointing out how the third star itself is very red, and the second one is fairly red. The values from Eichorn's study in 1970 are 7.22 9.65 10.71, with color indices -0.01, 0.71, 1.65.

My images show the third star almost disappearing in the g' blue-green filter that is close to V, while it is much brighter in the red r' filter. The second star has the same behavior but less so.

I don't know how accurate the Struve values are or if he was skewed by red in the color - but yes the second star seems much fainter than 9.1 in the equivalent V band - and Eichorn's value is 9.65 for the second and 10.71 for the third. My values are even fainter relative to the primary - but they aren't calibrated and they use different filters.

Frank

#28 WRAK

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Posted 22 January 2014 - 08:47 AM

Frank, regarding the red color of the companion see the attached photo of Chris Thuemen (central part with STF450, horizontal and vertical flipped to match approximately the orientation of your photo).
Wilfried

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#29 freestar8n

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Posted 22 January 2014 - 03:26 PM

Thanks - yes it does look red. I was mainly trying to get linear measurements through filters so I could do quantitative magnitude comparisons of the companion stars with the primary. This isn't trivial because the star spots aren't exactly round and they overlap.

I will probably do it again but will calibrate the magnitudes with comparison stars.

But there are other more recent published values for the photometric magnitudes of the stars, and they are fainter than the 9.1 value.

Frank






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