论文标题
使用CCD UBV和GAIA DR3数据对开放群集伯克利68和库存20的调查
An investigation of open clusters Berkeley 68 and Stock 20 using CCD UBV and Gaia DR3 data
论文作者
论文摘要
我们对开放型星团伯克利68和股票20进行了详细的光度法和星体分析。这是基于基于地面的CCD UBV光度计数据，该数据与空间基GAIA数据释放3光度法和星形统计相辅相成。伯克利68和51的198颗恒星被确定为库存20的群集成员。使用两色图来得出每个集群的红色和光度金属度。 The reddening for Berkeley 68 is $E(B-V)=0.520 \pm 0.032$ and $0.400 \pm 0.048$ mag for Stock 20. Photometric metallicity [Fe/H] is $-0.13 \pm 0.08$ dex for Berkeley 68, and $-0.01 \pm 0.06$ dex for Stock 20. Keeping as constant reddening and metallicity, we通过将等速线拟合到UBV和GAIA的颜色标记图，确定了簇的距离模量和年龄。光度距离为$ d = 3003 \ pm 165 $ berkeley 69和$ 2911 \ pm 216 $ pc for Stock 20。群集年龄为$ 2.4 \ pm 0.2 $ gyr和$ 50 \ $ 50 \ pm 10 $ berkeley 68和股票20。目前的质量斜率分别为$γ= 1.38 \ pm 0.71 $和$γ= 1.53 \ pm 0.39 $，分别为伯克利68和股票20。这些值与Salpeter（1955）的值兼容。放松时间分别为伯克利68和股票20分别为32.55 Myr和23.17 Myr。这些时间小于估计的群集年龄，表明两个簇都动态放松。由于径向速度数据不可用于库存20，因此仅针对伯克利68进行轨道整合。分析表明，伯克利68出生于太阳能圈外，属于银河系的薄盘组成部分。
We performed detailed photometric and astrometric analyses of the open star clusters Berkeley 68 and Stock 20. This was based on ground-based CCD UBV photometric data complemented by space-based Gaia Data Release 3 photometry and astrometry. 198 stars were identified as likely cluster members for Berkeley 68 and 51 for Stock 20. Two-color diagrams were used to derive the reddening and photometric metallicity for each cluster. The reddening for Berkeley 68 is $E(B-V)=0.520 \pm 0.032$ and $0.400 \pm 0.048$ mag for Stock 20. Photometric metallicity [Fe/H] is $-0.13 \pm 0.08$ dex for Berkeley 68, and $-0.01 \pm 0.06$ dex for Stock 20. Keeping as constant reddening and metallicity, we determined the distance moduli and ages of the clusters through fitting isochrones to the UBV and Gaia based color-magnitude diagrams. Photometric distances are $d=3003 \pm 165$ pc for Berkeley 69 and $2911 \pm 216$ pc for Stock 20. The cluster ages are $2.4 \pm 0.2$ Gyr and $50 \pm 10$ Myr for Berkeley 68 and Stock 20, respectively. Present-day mass function slopes were found to be $Γ= 1.38 \pm 0.71$ and $Γ= 1.53 \pm 0.39$ for Berkeley 68 and Stock 20, respectively. These values are compatible with the value of Salpeter (1955). The relaxation times were estimated as 32.55 Myr and 23.17 Myr for Berkeley 68 and Stock 20, respectively. These times are less than the estimated cluster ages, indicating that both clusters are dynamically relaxed. Orbit integration was carried out only for Berkeley 68 since radial velocity data was not available for Stock 20. Analysis indicated that Berkeley 68 was born outside the solar circle and belongs to the thin-disc component of the Milky Way.
