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Essam Elkholy

Publications and source records attributed to Essam Elkholy.

3 recordsLinked to original sources

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

Fractional Order Analysis of the Polytropic Models Applied to Exoplanets

Physical conditions deep within planets and exoplanets have yet to be measured directly, but indirect methods can calculate them. The polytropic models are one possible solution to this problem. In the present paper, we assume that the interiors of planets follow a polytropic equation of state. Hydrostatic equilibrium conditions are used to determine the overall structural properties of the constituent matter. In the frame of the conformable fractional derivatives, we use polytropic gas spheres to model the density profiles, pressure profiles, temperature distributions, and the mass-radius relations for the interiors of the initial stage of exoplanets. Planets of single chemical composition were used to study the behavior of the mass-radius relation, pressure distributions, and temperature distribution variation with the fractional parameter. We calculated 72 fractional models for the mass of protoplanets of 1MJ, 3MJ, and 10MJ (MJ is the mass of Jupiter), and the values of the polytropic index are n=0, 0.5, 1, 1.5, and the fractional parameter rang 0.75-1.

astro-ph.EP

First Results of Arar-Magnetometer Station in Saudi Arabia

This paper presents the first results of a new Arar-magnetometer station located (Geographic Coordinates: 30 58.5 N, 41 2.3 E) at Northern Border University in Saudi Arabia. The geomagnetic response detected by the station during a moderate magnetic storm of April 20, 2018, is examined as an initial study. The total magnetic field components measured by the station showed a prompt increase in coincident with the Sudden Storm Commencement (SSC) time measured by ACE satellite. The high rate of magnetic field digital data system of Arar-Magnetometer station with a sampling rate of 0.1 s allowed us to study the geomagnetic pulsation at the northern region of the Arabian Peninsula for the first time.

physics.space-ph