Article 2026-04-21 under-review v1

Discovery of a new open cluster as a companion to Czernik 38 cluster and its associated complex tide, using Gaia DR3

N
Nasser Ahmed National Research Institute of Astronomy and Geophysics

Abstract

Our earlier accepted research emphasized a detailed investigation of the Czernik 38 cluster through the utilization of Gaia DR3 data. We have discovered a new star cluster positioned 32 arcmin from its center, with coordinates α= 282.11 ± 0.05 and δ =4.56 ± 0.05 . Our suspicion is that this clump might form a new cluster (hereafter referred to as Nasser 1) and could be a companion to Czernik 38 in a binary cluster system. In this ongoing research, we aim to investigate this matter in depth and derive the physical parameters of the Nasser 1 cluster using Gaia data, in comparison to Czernik 38. We employed the pyUPMASK Python package with HDBSCAN algorithm to analyze membership of the Nasser 1 cluster to get its physical parameters. Our innovative method involves establishing a membership probability threshold value for each radius, as opposed to utilizing a singular value for the entire cluster. At each radius, we calculate the probability threshold value that yields a number of stars equivalent to that inferred from the King model. The foremost conclusion of our research is that this clump of stars is actually a new open star cluster. This newly identified cluster possesses a clearly defined CMD characterized by an age of 125.0± 12.30 Myr, a distance modulus of 12.87± 0.21 mag, and a significant color excess of 2.42 ± 0.09 ,respectively. In addition, it exhibits a distinct King profile. Further examination reveals that both clusters possess the same age, distance, proper motion, and radial velocity, even same high reddening value, within acceptable error limits. This implies that they together constitute a fantastic young primordial binary system characterized by a substantial reddening, located at the periphery of the Carina-Sagittarius spiral arm. Both clusters are affected by the impacts of differential rotation tides, as evidenced by their elongations in the direction of orbital motion. Furthermore, the Nasser 1 cluster is affected by an additional tide, specifically a gravitational tide caused by the Carina-Sagittarius spiral arm. In addition, the Gaussian mass function indicates that they were formerly an one cluster that has been violently turn apart by differential rotation during its orbital trajectory.

Citation Information

@article{nasserahmed2026,
  title={Discovery of a new open cluster as a companion to Czernik 38 cluster and its associated complex tide, using Gaia DR3},
  author={Nasser Ahmed},
  journal={Scientific Reports},
  year={2026},
  doi={https://doi.org/10.21203/rs.3.rs-9314492/v1}
}
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