# A detailed analysis of the Czernik 38 cluster and its associated tidal tail, utilizing Gaia DR3 and 2MASS

## TL;DR

This paper analyzes the Czernik 38 star cluster using Gaia and 2MASS data to study its structure, age, and newly discovered companion cluster.

## Contribution

The paper introduces a novel method of assigning membership probability at each radius in the cluster rather than using a single value.

## Key findings

- Czernik 38 has an elongated structure and a tidal tail aligned with its orbital path.
- A new star cluster was discovered 32 arcmin from Czernik 38, possibly a companion in a binary system.
- A new category of pre-main sequence stars was identified in the cluster, indicating active star formation.

## Abstract

This study provides a thorough investigation of the open cluster Czernik 38, employing photometric and astrometric data from Gaia DR3 and 2MASS. Our analysis refines the fundamental parameters of the cluster, including its structure, kinematics, evolutionary status, age, and morphology. To evaluate membership, we utilized the pyUPMASK Python package in conjunction with the HDBSCAN algorithm. The main focus of this research is our novel method of assigning a membership probability at each radius, instead of using a singular value for the entire cluster. One of the main outcomes of our research indicates that there is an elongated structure and a leading tidal tail that aligns with the orbital trajectory of the cluster. This tidal phenomenon arises due to orbital differential rotation. Furthermore, we have discovered a new star cluster located 32 arcmin from the center of Czernik. This cluster may serve as a companion to the Czernik 38 cluster in a binary cluster system or a complex colliding system; we will explore this further in subsequent research. According to Gaia, the distance modulus of the cluster and the color excess \documentclass[12pt]{minimal}
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\begin{document}$$E(G_{BP} - G_{RP})$$\end{document} are measured at 12.69\documentclass[12pt]{minimal}
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\begin{document}$$\pm$$\end{document} 0.08 mag and 2.40 \documentclass[12pt]{minimal}
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\begin{document}$$\pm$$\end{document} 0.04 mas, respectively. Additionally, from 2Mass, the distance modulus is 12.87 \documentclass[12pt]{minimal}
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\begin{document}$$\pm$$\end{document} 0.93 mag, while the color excess \documentclass[12pt]{minimal}
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\begin{document}$$\pm$$\end{document} 0.2 mag. Moreover, the cluster age is determined to be 115.0\documentclass[12pt]{minimal}
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\begin{document}$$\pm$$\end{document} 20.3 Myr. The components of proper motion (\documentclass[12pt]{minimal}
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\begin{document}$$\mu _{\delta }$$\end{document}) and the parallax (\documentclass[12pt]{minimal}
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\begin{document}$$\varpi$$\end{document}) are found as -2.41 \documentclass[12pt]{minimal}
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\begin{document}$$\pm$$\end{document} 0.328 mas yr\documentclass[12pt]{minimal}
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\begin{document}$$\pm$$\end{document} 1.063 mas yr\documentclass[12pt]{minimal}
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\begin{document}$$\pm$$\end{document} 0.083 mas, respectively. The calculated mean Gaia distances are roughly 3580.4 \documentclass[12pt]{minimal}
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\begin{document}$$\pm$$\end{document} 230.5 pc, which is in agreement with the photometric data from the Gaia and 2Mass data, within the error. There are 37 stars that exhibit radial velocity with average 46.1 \documentclass[12pt]{minimal}
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\begin{document}$$km s^{-1}$$\end{document}, which allows us to derive orbital parameters using the galpy python package. As a result, the cluster is moving parallel to the Galactic plane towards the Galactic center. 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 gravity compared to main sequence stars. This implies that there exists a significant rate of star formation within the Czernik 38 cluster. Furthermore, we have discovered many faint blue stars in Czernik 38, as well as in the newly identified clusters, which could potentially be white dwarf stars.