The Long-term Period Changes and Evolution of V1, a W Virginis Star in the Globular Cluster M12

Volume 47 number 2 (2019)

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Pradip Karmakar

Department of Mathematics, Madhyamgram High School (H.S.), Madhyamgram, Sodepur Road, Kolkata 700129, India; pradipkarmakar39@gmail.com

Horace A. Smith

Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824; smith@pa.msu.edu

Nathan De Lee

Department of Physics, Geology, and Engineering Technology, Northern Kentucky University, Highland Heights, KY 41099; deleenm@nku.edu

Abstract

We present new B, V, and I band photometry of the W Virginis-type variable star V1 in the globular cluster M12. Observations made from 1916 through 2018 show that during this interval the period of V1 has not shown a constant rate of period change, as might be expected were evolution alone responsible for the period changes. It has, however, shown period changes that appear to have a more abrupt character, probably both increases and decreases.