Czerink 38 is a remarkably plentiful open star cluster, distinguished by its significant number of stars and unique features resulting from its specific position in the Galaxy. However, this cluster has not been extensively studied. Consequently, we conducted an in-depth analysis of the young open cluster Czernik 38, utilizing photometric and astrometric data from Gaia DR3, alongside 2MASS data for comparative purposes with Gaia’s color-magnitude diagram (CMD). The objective of our analysis was to improve the parameters of Czernik 38 in relation to the Gaia DR3 era, particularly concentrating on its kinematics, dynamics, morphology and structural aspects. Moreover, To estimate membership, we employed the pyUPMASK Python package along with the HDBSCAN algorithm. The key focus of this investigation is our method of evaluating membership probability based on the radius of each shell in the studied cluster, utilizing King model, rather than applying a single probability value to the entire cluster. The key results of our study are summarized as follows: - In Czernik 38, we identified 938 \ (\) 61 member stars with a total mass of 2769. 7 \ (\) 59. 50 \ (M_\) inside radius 14. 36 \ (\) 7. 63 arcmin. We found that the cluster’s distance modulus was 12. 69 \ (\) 0. 08 mag, which is equivalent to 3448 \ (\) 362 pc. We also found the color excess \ (E (G ₁ - G ₑ) \) is 2. 40 \ (\) 0. 04 mag. Our findings have been confirmed by a comparison of the Gaia CMD with 2MASS data, which offers an additional viewpoint on the photometric characteristics of the cluster. The 2MASS distance modulus and the color excess \ (E (J-Ks) \) are found to be 12. 87 \ (\) 0. 93 mag (3749. 73 \ (\) 0. 93 pc) and 0. 89 \ (\) 0. 2 mag, respectively. We estimate the age of the cluster to be 115. 0 \ (\) 20. 3 Myr. One of the characteristics of this cluster is significant reddening, which is not uniformly distributed throughout the cluster. The proper motion components (\ (\), \ (\) ) and the parallax (\ (\) ) were measured as −2. 41 \ (\) 0. 328 mas yr \ (^-1\), −5. 263 \ (\) 1. 063 mas yr \ (^-1\) (tangential velocity is 93. 28 \ (\) 27. 16 km \ (s^-1\) ), and 0. 21 \ (\) 0. 083 mas, respectively. The mean distance derived from parallax measurements is approximately 3580. 4 \ (\) 230. 5 pc, which is in excellent agreement with the photometric data from Gaia and 2MASS data, within the associated uncertainties. We also identified 37 member stars with radial velocity data with average 46. 1 \ (\) 8. 54 km \ (s^-1\), allowing us to compute the orbital parameters of Czernik 38 using the galpy Python package. The Czernik 38 moves in Galactic plane toward the Galactic center. One of our main results is that: We identified a an elongated shape and a leading tidal tail aligned with the direction of orbital motion. This indicates that Chernik 38 is greatly affected by its orbital differential rotation, and this tide may be strengthened by the Galactic tide as it moves toward the Galactic center. The coordinates, proper motions, and distances of individual stars in the majority of open clusters display Gaussian distributions. Such distributions result from errors, not from actual physical values. Thus, any 3D distribution of stars or any density map based on coordinates will not relate to the true physical position distribution of stars, resulting in an artificial shape and and misleading results In general, we examined the area surrounding the cluster within a radius of 50 arcmin and employed a membership probability map in two dimensions \ (\) and \ (\), with probability threshold of greater than 80. %. Two separate groups of stars were identified. The first group corresponds to the Czernik 38 cluster, whereas the second group represents a newly discovered cluster. The initial investigations indicate that it displays a King profile and a color-magnitude diagram (CMD) consistent with the isochrone of Czernik 38. This may indicate a binary cluster or a complex colliding system located within a densely populated area of stars and interstellar material. We plan to explore this intriguing subject further in our upcoming research, offering comprehensive insights into the features of this newly identified cluster. We have identified a novel category of pre-main sequence stars that form a distinct branch in the right of Color-Magnitude Diagram (CMD). These stars exhibit lower temperatures and surface gravities compared to main sequence stars. This implies a considerable rate of star formation. The characteristic of this high star formation rate in this cluster corresponds with its relatively young age, significant reddening value, and its specific location amidst a concentration of stars and dense gases. In addition, we identified faint stars in both clusters, Czernik 38 and the new one, that exhibit bluer characteristics than main sequence stars, suggesting they could be white dwarf stars. These findings are intriguing because these stars are located in young clusters. In summary, alongside the photometric analysis, we offer significant insights into the structure, stellar populations, stellar evolution, as well as the kinematics and dynamics of Czernik 38, emphasizing the potential of Gaia DR3 data for comprehensive research on open star clusters. Moreover, the accurate astrometry data derived from Gaia has significantly modified our understanding of this cluster and has led to the discovery of new phenomena, thanks to Gaia.
Nasser M. Ahmed (Thu,) studied this question.