Long-Term Period Behavior of the Semiregular Variable V1 and the Type II Cepheids V2 and V3 in the Globular Cluster M10

Volume 50 number 1 (2022)

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Pradip Karmakar

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

Horace A. Smith

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

Wayne Osborn

Department of Physics, Central Michigan University, Mount Pleasant, MI 48859; wayne.osborn@cmich.edu

Peter B. Stetson

NRC-Herzberg, Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria BC V9E 2E7, Canada; Peter.Stetson@nrc.ca

Abstract

We present new U, B, V, RC, and IC-band photometry for the semiregular variable V1 and the type II Cepheids V2 and V3 in the globular cluster M10. Using old and new observations, we updated the most recent—1985—period change study of these variables. Observations made from 1912 through 2020 show that V1 has a recent average period of 48.9 days and, for the Cepheid variables, the 18.7-day pulsation period of V2 has decreased and the 7.8-day pulsation period of V3 has remained constant. The Fourier spectrum of the V-band observations of V2 yields a pattern of additional peaks at 0.5f0 and 1.5f0, where f0 is the frequency of the fundamental mode, similar to those that have been reported for W Virginis that indicate probable period-doubling.