arXiv subjects

Yasser Hendy

Publications and source records attributed to Yasser Hendy.

4 recordsLinked to original sources

arXiv2024

Open Superclusters II. Discovery of an Inactive Supercluster Including a New Star Cluster in the Solar Neighborhood

The number of known star clusters, associations, and moving groups in the vicinity of the Sun has increased significantly due to the use of Gaia data. We investigated the existence and properties of open superclusters (OSC) within 500 pc of the Sun, with a particular focus on a newly identified OSC, designated HC8. Using advanced Gaia-derived astrometric data and star cluster catalogs, we identify and analyze member stars of various clusters, deriving key parameters such as ages, distances, extinctions, and kinematic properties. Our findings reveal that HC8, a previously unrecognized OSC, encompasses several young clusters, including the newly discovered cluster Duvia 1. We provide a detailed examination of HC8's star formation history and its spatial and kinematic characteristics. This study contributes to the growing body of evidence supporting the existence of highly populated primordial groups and enhances our understanding of the formation and evolution of star clusters in the Galaxy.

astro-ph.SR↗

arXiv2024

Open superclusters I: The most populated primordial groups of open clusters in the third quadrant of the Galactic disc

An open supercluster (OSC) is defined as a cluster of at least six open clusters (OCs) born from the same giant molecular cloud (GMC). We survey the recent catalogs of OCs based on Gaia data and relevant literature to find 17 OSCs of the third galactic quadrant, along with 190 likely members of them. OSCs are frequent enough to be considered an extra class of objects in the hierarchy of star formation. Some of these supersystems are new and most of them contain more members than previously thought. The detailed study of some OSCs has leaded to the discovery of four new young clusters that are members of them, named Casado-Hendy 2 to 5. In certain instances, subgroups with distinct PMs or 3D positions have been found within an OSC, suggesting the presence of multiple generations of stars formed from several bursts of star formation within the same GMC. OSCs are typically unbound and tend to disintegrate on timescales of 0.1 Gyr. The present results support the Primordial Group hypothesis (Casado 2022) and suggest that globular clusters are not formed from the accretion of open superclusters, at least in the local Universe at late times.

astro-ph.GA↗

arXiv2023

Discovery and description of two young open clusters in the primordial group of NGC 6871

A primordial group of open clusters containing NGC 6871 is confirmed and described through Gaia DR3 data and the previous literature. It is a star-forming complex containing at least six young OCs, including Teutsch 8, FSR 198 and Biurakan 2. Two nearby OCs (Casado 82 and Casado-Hendy 1) are newly identified and studied in detail and found to be also members of the cited group. The parameters of the components are sufficiently similar to postulate the case of at least six clusters born from a single GMC. None of the cluster pairs of the group seems to be an authentic binary cluster, with the possible exception of the candidate pair Teutsch 8/FSR 198. Instead, NGC 6871 seems to be disintegrating, and the primordial group members appear to be dispersing out rapidly. Searching for new open clusters in the vicinity of young or grouped OCs using Gaia data is an efficient strategy to find new associated OCs forming primordial groups.

astro-ph.SR↗

arXiv2021

An investigation of open cluster Melotte 72 using Gaia DR2

The estimation of the main parameters of star clusters is significant in astrophysical studies. The most important aspect of using the Gaia DR2 survey lies in the positions, parallax, and proper motions of cluster stars with homogeneous photometry that make the membership probability determine with high accuracy. In this respect, depending on Gaia DR2 database, an analysis of the open star cluster Melotte 72 is taking place here. It is located at a distance of 2345+/-108 pc with an age of 1.0+/-0.5 Gyr. In studying the radial density profile, the radius is found to be 5.0+/-0.15 arcmin. The reddening, the luminosity and mass functions, the total mass of the cluster, and the galactic geometrical distances (X_Sun, Y_Sun, Z_Sun), and the distance from the galactic center (R_g ) have been estimated as well. Our study has shown a dynamical relaxation behavior of Melotte 72.

astro-ph.GA↗