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THE RR LYRAE VARIABLES AND HORIZONTAL BRANCH OF NGC 6656 (M22)<sup>,</sup>
Kunder, Andrea,Stetson, Peter B.,Cassisi, Santi,Layden, Andrew,Bono, Giuseppe,Catelan, Má,rcio,Walker, Alistair R.,Paredes Alvarez, Leonardo,Clem, James L.,Matsunaga, Noriyuki,Salaris, Maurizio American Institute of Physics 2013 The Astronomical journal Vol.146 No.5
<P>The first calibrated broadband UBVI time-series photometry is presented for the RR Lyrae variable stars in NGC 6656 (M22), with observations spanning a range of 22 years. We have also redetermined the variability types and periods for the RR Lyrae stars identified previously by photographic observations, revising the number of fundamental-mode RR Lyrae variables (RR0) to 10 and the number of first-overtone variables (RR1) to 16. The mean periods of the RR0 and RR1 variables are 〈P〉<SUB>RR0</SUB> = 0.66 ± 0.02 days and 〈P〉<SUB>RR1</SUB> = 0.33 ± 0.01 days, respectively, supporting an Oosterhoff II classification for the cluster. The number ratio of RR1-type to all RR-type variables is N<SUB>1</SUB>/N<SUB>RR</SUB> = 0.61, also consistent with an Oosterhoff II designation. Both the RR Lyrae stars' minimum light colors and the blue edge of the RR Lyrae instability strip suggest E( B – – V) = 0.36 ± 0.02 mag toward M22. Regarding the HB morphology of M22, we find (B-R)/(B+V+R) = +0.97 ± 0.1 and at least one 'gap' located in an unusual part of the blue HB, in the middle of the so-called hot HB stars.</P>
VARIABLE STARS IN LARGE MAGELLANIC CLOUD GLOBULAR CLUSTERS. III. RETICULUM
Kuehn, Charles A.,Dame, Kyra,Smith, Horace A.,Catelan, Má,rcio,Jeon, Young-Beom,Nemec, James M.,Walker, Alistair R.,Kunder, Andrea,Pritzl, Barton J.,De Lee, Nathan,Borissova, Jura American Institute of Physics 2013 The Astronomical journal Vol.145 No.6
<P>This is the third in a series of papers studying the variable stars in old globular clusters in the Large Magellanic Cloud. The primary goal of this series is to look at how the characteristics and behavior of RR Lyrae stars in Oosterhoff-intermediate systems compare to those of their counterparts in Oosterhoff-I/II systems. In this paper we present the results of our new time-series BVI photometric study of the globular cluster Reticulum. We found a total of 32 variables stars (22 RRab, 4 RRc, and 6 RRd stars) in our field of view. We present photometric parameters and light curves for these stars. We also present physical properties, derived from Fourier analysis of light curves, for some of the RR Lyrae stars. We discuss the Oosterhoff classification of Reticulum and use our results to re-derive the distance modulus and age of the cluster.</P>