Classification of Red Variables

American Association of Variable Star Observers (AAVSO)
Sat, 02/08/2020 - 21:24

Fellow LPVers, 

I hope everyone enjoyed the article I recently wrote about Betelgeuse. One item that came up with the article is the classification of Betelgeuse because it is physically so different than the stars typically written about in the LPV of the Month article. 

I did touch up in the article that Betelgeuse is currently classified as an SRc (which I'm told might change) and someone defined what that means. 

With this and with a recent forum thread questioning whether KL Cyg is still a Mira (an excellent question by the way), I revisited a paper on the classification of red variables (attached) authored by Dr. Mattei who was the AAVSO's director for over 30 years. 

The paper is easy to read and critically looks at our dividing lines between Miras, SRa, and SRb stars. It does not dive into SRc stars (which are luminous supergiants) and SRd stars, which are hot, still yellow supergiants. 

The paper also combs through AAVSO data identifies a handful of stars which may be misclassified. It may be an interesting project for the LP section to do something similar and try to find more. 

Please share your thoughts. 

Clear Skies, 

Rich Roberts (RIA) 

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