NOAO >   Observing Info >   Approved Programs >   2011B-0204

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Proposal Information for 2011B-0204


PI: James Nemec, Camosun College, jmn@isr.bc.ca
Address: Dept. of Physics & Astronomy, 3100 Foul Bay Road, Victoria, BC V8P 5J2, Canada

CoI: A.Walker & A.Kunder, Cerro Tololo Inter-American Observatory
CoI: Young-Beom Jeon, Korea Astronomy & Space Science Institute
CoI: Charles Kuehn, Michigan State University

Title: Blazhko, RRd and other `difficult' RR Lyrae Stars in LMC Outer-Halo Globular Clusters

Abstract: Studies of RR Lyr and other variable stars in nearby galaxies serve many purposes: establishing distances; testing ever-improving models of stellar evolution; allowing comparisons to be made with counterpart variable stars elsewhere in Local Group galaxies; and improving understanding of galaxy evolution. Our program aims to establish \it precise and \it accurate (B,V)-light curves, pulsation periods, oscillation modes and other pulsation properties (dP/dt rates, Blazhko periods, RRd stars) for the RR Lyr stars in the outer-halo globular clusters of the Large Magellanic Cloud. The physical characteristics of the stars ([Fe/H], L, T_\rm eff, mass, evolutionary phase) are then derived and compared with RR Lyr stars located elsewhere in the Local Group (in globular clusters, dwarf galaxies and in the general field) and with pulsation models. In general our target clusters lie \it beyond the OGLE and MACHO fields and thus provide important constraints for models of the LMC halo (NGC 2210 was observed by OGLE- III and serves as a useful control cluster). Approximately half of the RR Lyr stars we have been finding in these clusters are either RRd or Blazhko variables. We propose to acquire the time-series CCD images necessary to better define the physical characteristics of these `difficult' RR Lyr stars in the clusters NGC 1841, Reticulum, NGC 2257, NGC 1466 and NGC 2210.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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