新发现的Milky Way矮球状卫星Venaeu I中的变星
Variable Stars in the Newly Discovered Milky Way Dwarf Spheroidal Satellite Canes Venatici I
摘要：
在新近发现的犬座金星I矮椭球星系的84个候选变星中，我们已经确定了23颗RR型天琴座星和3颗可能的异常造父变星。18颗RRab型恒星的平均周期为<Pab>= 0.60 +/-0.01天。这个周期，以及这些恒星在周期振幅图中的位置，显示出犬座金星I可能是一个奥斯特霍夫中间型系统。对于<V>红化E（B-V）=0.03等，用天琴座RR型星的平均视星等= 22.17 +/-0.02得到的精确距离估计值为210 + 7/-5 kpc。我们给出了猎犬座VenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVenaVena红巨星分支的宽度和候选的异常造父变星在色星等图上的位置可能表明该星系拥有复杂的恒星星族，恒星的年龄从13 Gyr到0.6 Gyr。
英文摘要：
We have identified 23 RR Lyrae stars and 3 possible Anomalous Cepheids among 84 candidate variables in the recently discovered Canes Venatici I dwarf spheroidal galaxy. The mean period of 18 RRab type stars is <Pab> = 0.60 +/-0.01 days. This period, and the location of these stars in the period-amplitude diagram, suggest that Canes Venatici I is likely an Oosterhoff-intermediate system. The average apparent magnitude of the RR Lyrae stars <V> = 22.17 +/-0.02 is used to obtain a precision distance estimate of 210 +7/-5 kpc, for an adopted reddening E(B-V)=0.03 mag. We present a B,V color-magnitude diagram of Canes Venatici I that reaches V about 25 mag, and shows that the galaxy has a mainly old stellar population with a metal abundance near [Fe/H] = -2.0 dex. The width of the red giant branch and the location of the candidate Anomalous Cepheids on the color-magnitude diagram may indicate that the galaxy hosts a complex stellar population with stars from about 13 Gyr to as young as about 0.6 Gyr.
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