The RR Lyrae variables and Horizontal Branch of NGC6656 (M22)
| Autor: | Kunder, Andrea, Stetson, Peter B., Cassisi, Santi, Layden, Andrew, Bono, Giuseppe, Catelan, Marcio, Walker, Alistair R., Alvarez, Leonardo Paredes, Clem, James L., Matsunaga, Noriyuki, Salaris, Maurizio, Lee, Jae-Woo, Chaboyer, Brian C. |
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| Rok vydání: | 2013 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1088/0004-6256/146/5/119 |
| Popis: | The first calibrated broadband UBVI time-series photometry is presented for the RR Lyrae variable stars in NGC6656 (M22), with observations spanning a range of twenty-two 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 _{RR0}=0.66 \pm 0.02 d and _{RR1}=0.33 \pm 0.01 d, respectively, supporting an Oosterhoff II classification for the cluster. The number ratio of RR1- to all RR-type variables is N_1/N_{RR}=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 \pm 0.02 mag toward M22. Regarding the HB morphology of M22, we find (B-R)/(B+V+R)=+0.97 \pm 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. Comment: accepted to AJ |
| Databáze: | arXiv |
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