Light Curves and Period Changes for Type II Cepheids in the Globular Cluster M13 (Abstract)

Volume 43 number 2 (2015)

Horace A. Smith
Michigan State University, Department of Physics and Astronomy, Bio-Physical Sciences Building, 567 Wilson Road, East Lansing, MI 48824; smith@pa.msu.edu
Mary Anderson
P. O. Box 300, North Highlands, CA 95660; address email to H. A. Smith, smith@pa.msu.edu
Wayne Osborn
Central Michigan University and Yerkes Observatory, 118 Eagle Pointe Drive, Unit C, Delevan, WI 53115; wayne.osborn@cmich.edu
Andrew Layden
Bowling Green State University, Department of Physics and Astronomy, 104 Overman Hall, Bowling Green, OH 43403; laydena@bgsu.edu
Grzegorz Kopacki
Instytut Astronomiczny, Uniwersytet Wrocławski, Kopernika 11, 51-622Wrocław, Poland; kopacki@astro.uni.wroc.pl
Barton Pritzl
Department of Physics and Astronomy, University of Wisconsin Oshkosh, Oshkosh, WI 54901; pritzlb@uwosh.edu
Andrew Kelley
Bowling Green State University, Department of Physics and Astronomy, 104 Overman Hall, Bowling Green, OH 43403
Keith McBride
Bowling Green State University, Department of Physics and Astronomy, 104 Overman Hall, Bowling Green, OH 43403
Michael Alexander
Lehigh University, Department of Physics, 16 Memorial Drive E., Bethlehem, PA 18015; mia313@lehigh.edu
Charles Kuehn
University of Sydney, 44 Rosehill Street, Redfern, NSW 2042, Australia; kuehn@physics.usyd.edu.au
Aron Kilian
Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824
Eric King
Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824
David Carbajal
Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824
R. Lustig
Department of Physics and Astronomy, Macalester College, Saint Paul, MN 55105
Nathan De Lee
University of Nebraska at Kearney, 2401 11th Avenue, Kearney, NE 68849

Abstract

(Abstract only) B, V, and Cousins I-band light curves have been observed for the type II Cepheids V1, V2, and V6 in the globular cluster M13. These are relatively short period, BL Her-type Cepheids, with periods of 1.5, 5.1, and 2.1 days, respectively. Additional observations of V2 have been obtained from early photographic plates in the Yerkes Observatory archive. Long term period changes of these Cepheids have been determined by combining recent photometry with earlier observations that now extend back for more than a century. The observed period changes for V1, V2, and V6 are compared with the predictions of stellar evolution theory, under the assumption that the progenitors of the Cepheids were stars that at one time were on the blue horizontal branch.