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Denny Mandey

Publications and source records attributed to Denny Mandey.

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NGC 6134: a comprehensive study through photometric and kinematic analysis using Gaia DR3

Open clusters provide a unique laboratory for precisely constraining stellar age, distance, and metallicity, facilitating studies on exoplanet-host star correlations. Building on our previous membership study, we analyze photometric data to comprehensively characterize the open cluster NGC 6134 by determining its fundamental parameters, 3D spatial distribution, substructures, and mass segregation. Using the ASteCA code, we derive the cluster's parameters: $\mathrm{[Fe/H]} = 0.08 \pm 0.06$, $\log(t) = 9.14 \pm 0.01$, $d = 1064.43 \pm 15.19$ pc, and $A_\mathrm{v} = 1.03 \pm 0.05$ mag. Independent Bayesian inference of individual member distances yields a cluster distance of $1070.83 \pm 2.50$ pc, in excellent agreement with the ASteCA results. Spatial substructures are successfully mapped using Gaussian Mixture Models, revealing a three-component distribution corresponding to the cluster's core, tidal tail, and halo. Furthermore, Minimum Spanning Tree analysis indicates that the observed mass segregation is driven by dynamical evolution rather than primordial origins. Finally, our analysis of the cluster's Color--Magnitude Diagram identifies probable blue straggler stars and a main-sequence gap, which we conclude is strongly linked to the cluster's binary fraction.

astro-ph.GA

Prospects of Application of Semi-Definite Programming to Determine Orbital Parameters of the Binary Systems Observed at Bosscha Observatory

Most methods of orbit determination are often difficult for numerical implementations since they are developed before the computer era. The recently developed mathematical technique of semi-definite programming (SDP) has been implemented for many problems in scientific fields including astrometry. This is a good opportunity to resolve orbits of binary systems located in the southern hemisphere since more than seventy years Bosscha Observatory had been continuously conducting observations of binary systems. Here we describe prospects of application of SDP for deriving orbital parameters of binary systems using data supplied by Bosscha Observatory that has been published in the Centre de Donnees astronomiques de Strasbourg. This study will support observers at Bosscha Observatory to appropriately select target stars belong to binary systems for their ongoing researches. Since SDP is a powerful scheme, free trial-and-error and human-independent judgment, we suggest that SDP may become a standard method for determining orbital parameters of binary systems.

astro-ph.SR