The RR Lyrae variables and Horizontal Branch of NGC6656 (M22)

Дата и время публикации : 2013-08-29T19:52:54Z

Авторы публикации и институты :
Andrea Kunder
Peter B. Stetson
Santi Cassisi
Andrew Layden
Giuseppe Bono
Marcio Catelan
Alistair R. Walker
Leonardo Paredes Alvarez
James L. Clem
Noriyuki Matsunaga
Maurizio Salaris
Jae-Woo Lee
Brian C. Chaboyer

Ссылка на журнал-издание: Ссылка на журнал-издание не найдена
Коментарии к cтатье: accepted to AJ
Первичная категория: astro-ph.SR

Все категории : astro-ph.SR

Краткий обзор статьи: 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 <P>_{RR0}=0.66 pm 0.02 d and <P>_{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.

Category: Physics