We conducted the stellar photometry using the archive images of the Hubble Space Telescope of the dwarf irregular galaxy Cas 1 located near the Milky Way. Blue supergiants detected in the obtained Hertzsprung-Russell diagram are concentrated in star-forming regions. We found that the red star branch consists of numerous AGB stars and a small number of brighter red supergiants. In the luminosity function of the peripheric red giants and AGB stars selected, the TRGB discontinuity is observed with I = 23.^m67 which corresponds to the beginning of the red giant branch. Using the TRGB method, we determined the distance modulus to the Cas 1 (m - M) = 26.01 ± 0.08 which corresponds to the distance D = 1.6 ± 0.1 Mpc. This estimate shows that the galaxy is near the Local Group and isolated from other galaxies. The absolute luminosity of Cas 1 based on the new distance measurement is M_V = -14.2, i.e. it is definitely a dwarf galaxy. The position of the red giant branch of AGB stars in the Hertzsprung-Russell diagram and measured metallicity of red giants shows that the galaxy Cas 1 has a very low metallicity [Fe/H] = -2.8.

中文翻译：

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距银河附近不规则银河Cas 1的距离

我们使用位于银河附近的不规则矮星系Cas 1的哈勃太空望远镜的档案图像进行了恒星测光。在获得的Hertzsprung-Russell图中检测到的蓝色超巨星集中在恒星形成区域。我们发现红星分支由许多AGB恒星和少量明亮的红色超巨星组成。在的周围红色巨头和AGB星选择的光度函数，观察到的不连续性TRGB与我= 23^米67，其对应于红巨分支的开始。使用TRGB方法，我们确定到Cas 1（m-M）= 26.01±0.08的距离模量，它对应于距离D= 1.6±0.1 Mpc。此估计值表明该星系位于本地群附近，并且与其他星系隔离​​。根据新的距离测量，Cas 1的绝对光度为M _V = -14.2，即绝对是矮星系。AGB的红巨分支的位置中的红色巨头示出了赫罗图和测量金属丰度，所述星系CAS 1具有非常低的金属丰度的[Fe星/ H] = - 2.8。