arXiv subjects

Aly Haroon

Publications and source records attributed to Aly Haroon.

6 recordsLinked to original sources

arXiv2026

Exploring the Near Galactic Centre: A Comprehensive Study of Bulge OCs HSC 25, HSC 37, HSC 2878 Utilising Gaia DR3 Data

We present a comprehensive photometric and kinematic study of the open clusters HSC 25, HSC 37, and HSC 2878, located in the innermost regions of the Galactic disc. Utilizing data from Gaia DR3 and the UPMASK membership algorithm, we identify 44, 55, and 112 most probable members for HSC 25, HSC 37, and HSC 2878, respectively. The mean proper-motion components are obtained as (-5.901 +/- 0.41, -6.213 +/- 0.40), (-3.231 +/- 0.56, -4.564 +/- 0.47), and (-3.830 +/- 0.51, -5.198 +/- 0.44) mas yr^-1 for HSC 25, HSC 37, and HSC 2878, respectively. The open clusters span a broad range of evolutionary stages, with estimated ages of log(t/yr) = 8.38 +/- 0.08, 7.04 +/- 0.09, and 9.04 +/- 0.09, and corresponding heliocentric distances of 7.36 +/- 0.37, 6.79 +/- 0.18, and 6.17 +/- 0.22 kpc. The obtained metallicities are 0.0388 +/- 0.0039, 0.0259 +/- 0.0028, and 0.0209 +/- 0.0023, respectively. Total mass estimates are 135, 755, and 204 solar masses, respectively, highlighting notable differences in stellar content across the clusters. An analysis of dynamical relaxation times suggests that HSC 25 and HSC 2878 are dynamically evolved, whereas the much younger HSC 37 is still in an early phase of dynamical evolution. The high space velocities and orbital parameters of these clusters reveal significant deviations from typical disc kinematics. HSC 25 and HSC 37 exhibit eccentric orbits and small perigalactic distances, consistent with dynamically heated or accreted origins within the Galactic bulge. In contrast, HSC 2878's relaxed, planar orbit suggests in situ bulge membership despite its age. These findings point toward a heterogeneous dynamical origin for the clusters, with implications for star formation and evolution in the inner Milky Way.

astro-ph.GA↗

arXiv2026

Comprehensive Gaia DR3-Based Astrometric, Photometric, and Kinematic Studies of the Binary Open Cluster $h$ and $\chi$ Persei

In the Gaia era, a comprehensive analysis of the binary open clusters NGC 869 (h Persei) and NGC 884 (chi Persei) system has been conducted to investigate its structural, astrophysical, kinematic, and Galactic orbital properties, along with its dynamical evolution. By applying the UPMASK algorithm to Gaia astrometric data for the estimation of cluster membership probabilities, it has been determined that 808 stars in NGC 869 and 707 stars in NGC 884 exhibit the highest statistical likelihood of being cluster members. The fundamental astrophysical parameters of the clusters were inferred within a Bayesian framework using Gaia data and PARSEC stellar evolutionary isochrones, through the application of the Markov Chain Monte Carlo (MCMC) technique. The estimated parameters are: colour excess E(B-V) = 0.516 +0.17/-0.24 mag and 0.516 +0.22/-0.33 mag, distances 2376 +301/-278 and 2273 +230/-290 pc, ages log(t/yr) = 7.31 +0.17/-0.32 and log(t/yr) = 7.30 +0.13/-0.29, and metallicities [Fe/H] = -0.24 +/- 0.12 and [Fe/H] = -0.25 +/- 0.12 dex for NGC 869 and NGC 884, respectively. Since spectroscopic observations are not available for the clusters, SED analysis was employed for the member stars, yielding results consistent with those obtained using the MCMC method. Kinematic and Galactic orbital analyses suggest that the open clusters originated in nearby regions of the Galaxy. This interpretation is supported by their similar space velocities and Galactic orbital parameters. Furthermore, orbital integration over 1 Gyr indicates a potential interaction between the clusters within the next 11 Myr. This study provides strong evidence of a common origin and a possible future dynamical interaction, contributing valuable insights into the formation and evolution of binary open clusters in the Milky Way.

astro-ph.GA↗

arXiv2025

Enhancing SED-Based Astrometric, Photometric, and Kinematic Studies of SAI 72 and SAI 75 Using Gaia DR3

This study investigates the open clusters SAI 72 and SAI 75 using Gaia DR3 data, employing the Automated Stellar Cluster Analysis (ASteCA) tool to determine their structural and fundamental properties, including center coordinates, size, age, distance, mass, luminosity, and kinematics. Based on membership probabilities (P >= 50%), we identified 112 and 115 stars as probable members of SAI 72 and SAI 75, respectively. Radial density profile (RDP) analysis yielded cluster radii of 2.35 arcmin for SAI 72 and 2.19 arcmin for SAI 75. The spectral energy distribution (SED) fitting was performed to refine metallicity, distance, and color excess parameters, ensuring consistency within 1 sigma of isochrone-based estimates. Isochrone fitting of the color-magnitude diagram (CMD) suggests ages of 316 Myr and 302 Myr, with corresponding distances of 3160 +/- 80 pc and 3200 +/- 200 pc. We derived their Galactic positions, projected distances (X_sun, Y_sun), and vertical displacements (Z_sun). Mass function analysis estimates cluster masses of 612 +/- 174 solar masses for SAI 72 and 465 +/- 90 solar masses for SAI 75. Kinematic studies indicate that both clusters have reached dynamical equilibrium. The AD diagram method provided convergent point coordinates of (A, D)_o = (97.016 +/- 0.09, 4.573 +/- 0.05) for SAI 72 and (99.677 +/- 0.10, 1.243 +/- 0.09) for SAI 75. Orbital analysis confirms that both clusters follow nearly circular trajectories with low eccentricities and minor variations in apogalactic and perigalactic distances. Furthermore, we determine that SAI 72 and SAI 75 originated beyond the solar circle at R_Birth = 10.825 +/- 0.068 kpc and R_Birth = 9.583 +/- 0.231 kpc, respectively. Their maximum heights above the Galactic plane, Z_max, are 109 +/- 9 pc for SAI 72 and 232 +/- 24 pc for SAI 75, reinforcing their classification as part of the young stellar disc population.

astro-ph.GA↗

arXiv2025

An In-depth Analysis of Photometric and Kinematic Characteristics of SAI 16, SAI 81 and SAI 86 Open Clusters Utilizing Gaia DR3

This study comprehensively analyzes three open star clusters: SAI 16, SAI 81, and SAI 86 using Gaia DR3 data. Based on the ASteCA code, we determined the most probable star candidates (P >= 50%) and estimated the number of star members of each cluster as 125, 158, and 138, respectively. We estimated the internal structural parameters by fitting the King model to the observed RDPs, including the core, limited, and tidal radii. The isochrone fitting to the color-magnitude diagram provided log(age) values of 9.13 +/- 0.04, 8.10 +/- 0.04, and 8.65 +/- 0.04 and distances of 3790 +/- 94 pc, 3900 +/- 200 pc, and 3120 +/- 30 pc for SAI 16, SAI 81, and SAI 86, respectively. We also calculated their projected distances from the Galactic plane (X_sun, Y_sun) as well as their vertical distances (Z_sun), Galactocentric distances (R_gc), and total masses (M_C) in solar units, which are about 142 +/- 12, 302 +/- 17, and 192 +/- 14 for SAI 16, SAI 81, and SAI 86, respectively. Examining the dynamical relaxation state indicates that all three clusters are dynamically relaxed. By undertaking a kinematic analysis of the cluster data, the space velocity was determined. We calculated the coordinates of the apex point (A_o, D_o) using the AD diagram method along with the derivation of the solar motion parameters (S_sun, l_A, b_A). Through our detailed dynamic orbit analysis, we determined that the three SAI clusters belong to the young stellar disc, confirming their membership within this component of the Galactic structure.

astro-ph.GA↗

arXiv2025

Comprehensive Analysis of Middle-Aged Open Cluster NGC 6793 in Vulpecula via Gaia DR3 Data

We conducted an in-depth analysis of NGC 6793 open cluster via Gaia DR3 data, including astrometric, spectroscopic, and photometric measurements. Selection of 147 stars, which show membership probabilities $P\geq0.5$ were classified as likely members. The mean trigonometric parallaxes and proper-motion components of the cluster were found to be $\varpi = 1.674 \pm0.045$ mas and ($\mu_{\alpha}\cos \delta$,~$\mu_{\delta}$) =($3.814\pm0.031$,~$3.547\pm0.034$) mas yr$^{-1}$. Fundamental astrophysical parameters of NGC 6793 are derived simultaneously as $t$ = $650 \pm 50$ Myr, $\mu$ = $9.508\pm0.070$ mag, and $E(G_{\rm BP}-G_{\rm RP})$ = $0.361 \pm 0.035$ mag. Additionally, the cluster's luminosity function analysis reveals the $G$-absolute magnitude limit of the most likely stars, indicating a well-defined stellar population. The total mass of the cluster, determined through the mass function (MF) and considering stars with membership probabilities $P \geq 0.5$, was estimated as 139 $\pm$ 12 $M/M_{\odot}$. The slope of the MF was found to be $\Gamma = 1.40 \pm 0.26$, a result consistent with the Salpeter value. The kinematic analyses present velocity ellipsoid parameters as well as the convergent point $(A_{\rm o},~D_{\rm o}) = \left(85^{\circ}.85 \pm 0^{\circ}.11,~3^{\circ}.12 \pm 0^{\circ}.57\right)$. Analyses have shown that it is moving in a box-shaped orbit beyond the Sun's galactic radius and belongs to the thin disk population of the Milky Way. The calculated relaxation time suggests that NGC 6793 has reached a dynamically relaxed state, where the dynamical evolution parameter $\tau$ significantly exceeds one. These results highlight both the cluster's internal stability and its connection to the thin disc population.

astro-ph.GA↗

arXiv2025

Study of Open Star Clusters Using the Gaia DR3: I- Poorly Studied King 2 and King 5

In this study, we utilize photometric and kinematic data from \textit{Gaia} DR3 and the {\sc ASteCA} package to analyze the sparsely studied open clusters, King 2 and King 5. For King 2, we identify 340 probable members with membership probabilities exceeding 50\%. Its mean proper motion components are determined as $(\mu_\alpha\cos\delta,~\mu_\delta) = (-1.407 \pm 0.008, -0.863 \pm 0.012)$ mas yr$^{-1}$, and its limiting radius is derived as $6.94_{-1.06}^{+0.22}$ arcminutes based on radial density profiles. The cluster has an estimated age of $4.80 \pm 0.30$ Gyr, a distance of $6586 \pm 164$ pc, and a metallicity of $\text{[Fe/H]} = -0.25$ dex ($z = 0.0088$). We detect 17 blue straggler stars (BSSs) concentrated in its core, and its total mass is estimated to be $356 \pm 19~M_{\odot}$. The computed apex motion is $(A_o,~D_o) = (-142^\circ.61 \pm 0^\circ.08, -63^\circ.58 \pm 0^\circ.13)$. Similarly, King 5 consists of 403 probable members with mean proper motion components $(\mu_\alpha\cos\delta,~\mu_\delta) = (-0.291 \pm 0.005, -1.256 \pm 0.005)$ mas yr$^{-1}$ and a limiting radius of $11.33_{-2.16}^{+5.45}$ arcminutes. The cluster's age is determined as $1.45 \pm 0.10$ Gyr, with a distance of $2220 \pm 40$ pc and a metallicity of $\text{[Fe/H]} = -0.15$ dex ($z = 0.0109$). We identify 4 centrally concentrated BSSs, and the total mass is estimated as $484 \pm 22~M_{\odot}$. The apex motion is calculated as $(A_o,~D_o) = (-115^\circ.10 \pm 0^\circ.09, -73^\circ.16 \pm 0^\circ.12)$. The orbital analysis of King 2 and King 5 indicates nearly circular orbits, characterized by low eccentricities and minimal variation in their apogalactic and perigalactic distances. King 2 and King 5 reach maximum heights of $499 \pm 25$ pc and $177 \pm 2$ pc from the Galactic plane, respectively, confirming their classification as young stellar disc population.

astro-ph.GA↗