RR Lyrae Variable Stars in the Dwarf Spheroidal Galaxy Leo I
RR Lyrae Variable Stars in the Dwarf Spheroidal Galaxy Leo I
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矮球状星系 Leo I 中的 RR Lyrae 变星
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
L. Di Fabrizio
中科院分区：
文献类型：
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作者：
E. Held;G. Clementini;L. Rizzi;Y. Momany;I. Saviane;L. Di Fabrizio
我们报告在矮椭球星系 Leo I 中发现了大量 RR Lyrae 变星。基于使用 ESO 广域成像仪拍摄的该星系的 40 V 和 22 B 图像，我们迄今为止在托管星系主体的两个 CCD 中识别出了 74 颗候选 RR Lyrae 变星。已经获得了其中 54 颗的光变化和脉动周期的完整覆盖，其中 47 颗是贝利 ab 型 RR 天琴座 (RRab) 星，7 颗是 c 型 RR 天琴座 (RRc) 星。目前已确认的 RRab 星样本的周期分布在 P = 0.60 天时达到峰值，最小周期为 0.54 天。脉动特性表明狮子座 I 具有中间的奥斯特霍夫类型，类似于本星系群和 LMC 中的其他矮星系。然而，ab型变星的最小周期相当长，并且长周期和大振幅的RRab星数量众多，表明狮子座一号的老星群的大部分更像是奥斯特霍夫II型球状星团。最直接的解释是，狮子座一号的天琴座RR恒星中存在一定的金属丰度范围，其中有大量金属非常贫乏的恒星。或者，这些奥斯特霍夫 II 型变星可能会更加进化。天琴座 RR 星在整个周期内的平均视星等为 ⟨V(RR)⟩ = 22.60 ± 0.12 星等，从而得出狮子座 I 在“长”距离尺度上的距离模数 (m-M)V, 0 = 22.04 ± 0.14 星等。
We report the discovery of a significant population of RR Lyrae variable stars in the dwarf spheroidal galaxy Leo I. Based on 40 V and 22 B images of the galaxy taken using the ESO Wide-Field Imager, we have so far identified 74 candidate RR Lyrae stars in two CCDs hosting the main body of the galaxy. Full coverage of the light variations and pulsation periods have been obtained for 54 of them, 47 of which are Bailey ab-type RR Lyrae (RRab) stars and seven are c-type RR Lyrae (RRc) stars. The period distribution of the presently confirmed sample of RRab stars peaks at P = 0.60 days, with a minimum period of 0.54 days. The pulsational properties indicate an intermediate Oosterhoff type for Leo I, similar to other dwarf galaxies in the Local Group and the LMC. However, the rather long minimum period of the ab-type variable stars, and the significant number of RRab stars with long period and large amplitude, suggest that the bulk of the old population in Leo I is more like the Oosterhoff type II globular clusters. The most straightforward interpretation is that a range in metallicity is present among the RR Lyrae stars of Leo I, with a significant population of very metal-poor stars. Alternatively, these Oosterhoff type II variable stars could be more evolved. The average apparent magnitude of the RR Lyrae stars across the full cycle is ⟨V(RR)⟩ = 22.60 ± 0.12 mag, yielding a distance modulus (m-M)V, 0 = 22.04 ± 0.14 mag for Leo I on the "long" distance scale.