arXiv subjects

M. I. Nouh

Publications and source records attributed to M. I. Nouh.

At least 19 recordsLinked to original sources

arXiv2021

Fundamental parameters of some B-type stars using NOAO Indo-U.S. Library

In the present article, we present a spectroscopic analysis of 83 field B-type stars from NOAO Indo-U.S. Library. We calculated the fundamental parameters e.g effective temperatures, surface gravities, and rotational velocities using Barbier-Chalonge-Divan (BCD) method and line blanketed LTE/NLTE model atmospheres. The projected rotational velocity was estimated by fitting the Mg II4481 Å line profile with theoretical lines calculated from LTE/NLTE models. The evolutionary masses for the program stars are estimated using the evolutionary models. In most of the cases, the present study gives fair agreement with earlier investigations and is even more accurate in some cases.

astro-ph.SR↗

arXiv2021

Kinematics And Ellipsoidal Motion Of The Mid To Late M-Type Stars

Truly, kinematics in the Solar neighborhood has provided important information both for the structure and for the evolution of the Galaxy since the early 20th century. The relationship between Oort constants and the ratio of the velocity dispersion are important quantities in stellar kinematics. In the present paper, we calculated the kinematical parameters and the Oort constants of various samples of late to intermediate M-type stars. We calculated the velocity dispersion (σ_1,σ_2,σ_3 ) in units of km s-1 for the samples under study. The longitude of the vertex (l_2 ) having negative values with our analysis; i.e., the program I (538 stars), l_2 =-0_.^o 5410, program II (100 stars), l_2=-0_.^o 4937 and program III (60 stars), l_2=-0_.^o 9495. We calculate the Oort constants as A=14.69+-0.61 km s-1 kpc-1 and B=-16.70+-0.67 km s-1 kpc-1, and the rotational velocity V_o=257.38+-9.40 km s^(-1). A possible explanation for the overestimated values of the second Oort constants has been presented.

astro-ph.GA↗

arXiv2021

Stability Analysis of Relativistic Polytropes

A main question in astrophysics and cosmology has been the severe stability of the astrophysical objects, whether a particular equilibrium configuration is stable. In this article, we study the relativistic self-gravitating, hydrostatic spheres with a polytropic equation of state , considering structures with the polytropic indices and illustrates the results for the relativistic parameters . We determined the critical relativistic parameter at which the mass of the polytrope has a maximum value and represents the first mode of radial instability. For n=1 (0.5)-2.5, stable relativistic polytropes occur for less than the critical values 0.42, 0.20, 0.10, and 0.04 respectively, while unstable relativistic polytropes are obtained when the relativistic parameter is greater than the same values. When n=3.0 and, energetically unstable solutions have occurred. The results of critical values obtained in this paper for different polytropic indices are in full agreement with those evaluated by several authors. Comparisons between analytical and numerical solutions of the given relativistic functions provide a maximum relative error of order.

gr-qc↗

arXiv2020

A Study of the Time Variability and Line Profile Variations of kappa Dra

In this study, we present a spectroscopic analysis of the bright Be star kappa Dra. Two independent sets of radial velocity velocities (RV) measurements were obtained by direct measurement and using a line profile disentangling technique. Using a combination of the solutions found by the codes FOTEL and KOREL, we revisited the binary nature of kappa Dra and derived improved orbital elements. From the RVs of the Balmer lines and also from some strong metallic lines we found that all RVs variations are phase-locked with the orbital period. V/R variations were obtained for H_alpha, H_beta, H_gamma and some other photospheric lines and they are found to be phase-locked with the orbital motion. A moving absorption bump superimposed over the H_alpha and H_beta emission line profiles was detected. The orbital solutions for kappa Dra were derived assuming a circular orbit with a period 61.5549 day and K = 6.81 km/s . The question of the line profile variability was discussed. We attempted to search for absorption or emission lines of the unresolved secondary component, we failed to find them.

astro-ph.SR↗

arXiv2020

Prediction of the Atmospheric Fundamental Parameters from Stellar Spectra Using Artificial Neural Network

Innovation in the ground and space-based instruments has taken us into a new age of spectroscopy, in which a large amount of stellar content is becoming available. So, automatic classification of stellar spectra became subjective in recent years due to the availability of large observed spectral database as well as the theoretical spectra. In the present paper, we develop an Artificial Neural Network (ANN) algorithm for automated classification of stellar spectra. The algorithm has been applied to extract the fundamental parameters of some hot helium rich white dwarf stars observed by the Sloan Digital Sky Survey (SDSS) and B-type spectra observed at Onderjove observatory. We compared the present fundamental parameters and those from a minimum distance method to clarify the accuracy of the present algorithm where we found that, the predicted atmospheric parameters for the two samples are in good agreement for about 50% of the samples. A possible explanation for the discrepancies found for the rest of the samples is discussed.

astro-ph.SR↗

arXiv2019

X-ray warm absorber variability of the Seyfert Galaxy Arakelian 564

The aim of this paper is to study the variability of the warm absorber "clouds of ionised gas within AGN", for the Seyfert 1 galaxies Arakelian 564. The X-ray spectra for four XMM-Newton observations of this object are analysed in EPIC and RGS instruments. These four observations covered a period of eleven years. There are some changes in the ionisation parameter ($ ξ$) of the absorbing matter from one observation to another( $\logξ=0.889 \pm 3.11 \times 10^{-2}$ for year 2000 observation and $0.437 \pm 7.60 \times 10^{-2}$ for year 2001 ). Also the X-ray soft excess is studied for the four observation by using two blackbody parameters in EPIC spectra ( the first black-body temperature is $\sim $ $0.129 \pm 2.04 \times 10^{-3}$ Kev and the second is $\sim 1.74 \pm 7.6 \times {10^{-2}}$ Kev) and one black body parameter in RGS spectra.

astro-ph.HE↗

arXiv2018

PPMXL and Gaia Morphological Analysis of Melotte 22 (Pleaides) and 25 (Hyades)

In this article, we present a morphological study of the well-known extended sized open clusters in the sky, Melotte 22 (Pleiades) and Melotte 25 (Hyades) with J, H, and Ks regions due to Gaia DR2 and PPMXL catalogues. Based on proper motions of these clusters, we extract our candidates and hence constructing fitting isochrones with Solar metallicity Z = 0.019, log (age) = 8.2 +- 0.05 for Melotte 22, and metallicity Z = 0.024, log (age) = 8.9 +- 0.10 for Melotte 25. Some photometric parameters are estimated, e.g. cluster heliocentric distances are 135 +- 3.6 and 47.51 +- 2.15 pc respectively, luminosity and mass functions with mass-luminosity relation MLR of the second order polynomial, and we have estimated the masses of Melotte 22 and Melotte 25 as 662.476 +- 25.73 Msun and 513.819 +- 22.65 Msun. The relaxation times of these clusters are smaller than the estimated cluster ages, which indicate that these clusters are dynamically relaxed. The second part is devoted to some kinematics of these clusters due to internal and/or motion of members, the apex position is 95.60 +- 0.10, -48.21 +- 0.14 for Melotte 22, and 96.72 +- 1.15, 5.66 +- 0.12 for Melotte 25. Also we have determined the components of space velocity and the cluster centers in pc as well as elements of the Solar motion. The results are in good agreement with those in the literature.

astro-ph.SR↗

arXiv2017

Light Curve Modelling and Evolutionary Status of the Short Period Binary 1SWASP J092328.76+435044

Light curve modeling for the newly discovered system 1SWASP J092328.76+435044 was carried out by using a new BVR complete light curves. A spotted model was applied to treat the asymmetry of the light curves. The output model was obtained by means of Wilson-Devinney code, which reveals that the massive component is hotter than the less massive one with about ΔT ~ 400K. A total of 8 new times of minima were estimated. The evolutionary state of the system components was investigated based on the estimated physical parameters.

astro-ph.SR↗

arXiv2017

An Extensive Photometric Investigation of the W UMa System DK Cyg

DK Cyg (P = 0.4707) is a W Ursae Majoris type eclipsing binary system that undergoes complete eclipses. All the published photoelectric data have been collected and utilized to re-examine and update the period behavior of the system. A significant period increase with rate of 12.590x10-11 day/cycle was calculated. New period and ephemeris has been calculated for the system. A long term photometric solution study was performed and a light curve elements were calculated. We investigated the evolutionary status of the system using theoretical evolutionary models.

astro-ph.SR↗

arXiv2017

White Dwarf Stars as Polytropic Gas Spheres

Due to the highly degeneracy of electrons in white dwarf stars, we expect that the relativistic effects play very important role in these stars. In the present article, we study the properties of the condensed matter in white dwarfs using Newtonian and relativistic polytropic fluid sphere. Two polytropic indices (namely n=3 and n=1.5) are proposed to investigate the physical characteristics of the models. We solve the Lane-Emden equations numerically.. The results show that the relativistic effect is small in white dwarf stars.

astro-ph.SR↗

arXiv2017

Approximate solution to the fractional Lane-Emden type equations

In this paper, approximate solutions for a class of fractional Lane - Emden type equations based on the series expansion method are presented. Various examples are introduced and discussed. The recurrence relation for the components of the approximate solution is constructed. In the standard integer order derivative, it is shown that the results are the same as those obtained by Adomian decomposition method, homotopy perturbation method, modified Laplace decomposition method and variational iteration method.

math.CA↗

arXiv2017

Approximate Analytical Solutions to the Relativistic Isothermal Gas Spheres

In this paper, we introduce a novel analytical solution to Tolman-Oppenheimer-Volkoff (TOV) equation, which is ultimately a hydrostatic equilibrium equation derived from the general relativity in the framework of relativistic isothermal spheres. Application of the traditional power series expansions on solving TOV equation results in a limited physical range to the convergent power series solution. To improve the convergence radii of the obtained series solutions, a combination of the two techniques of Euler-Abel transformation and Pade approximation has done. The solutions are given in \exi-θand \exi-μphase planes taking into account the general relativistic effects σ= 0.1, 0.2 and 0.3. An Application to a neutron star has done. A Comparison between the results obtained by the suggested approach in the present paper and the numerical one indicates a good agreement with a maximum relative error of order 10-3, which establishes the validity and accuracy of the method. The procedure we have applied accelerated the power series solution with about ten times than of traditional one.

gr-qc↗

arXiv2016

Statistical Study of Visual Binaries

In this paper, some statistical distributions of wide pairs included in Double Star Catalogue are investigated. Frequency distributions and testing hypothesis are derived for some basic parameters of visual binaries. The results reached indicate that, it was found that the magnitude difference is distributed exponentially, which means that the majority of the component of the selected systems is of the same spectral type. The distribution of the mass ratios is concentrated about 0.7 which agree with Salpeter mass function. The distribution of the linear separation appears to be exponentially, which contradict with previous studies for close binaries.

astro-ph.SR↗

arXiv2016

Orbital solution and evolutionary state for the eclipsing binary 1SWASP J080150.03+471433.8

We present an orbital solution study for the newly discovered system 1SWASP J080150.03+471433.8 by means of new CCD observations in VRI bands. Our observations were carried out on 25 Feb. 2013 using the Kottamia optical telescope at NRIAG, Egypt. 12 new times of minima were estimated and the observed light curves were analysed using the Wilson-Devinney code. The accepted orbital solution reveals that the primary component of is more massive and hotter than the secondary one by about 280K. The system is an over-contact one with fillout ratio ~ 29% and is located at a distance of 195 Pc. The evolutionary status of the system is investigated by means of stellar models and empirical data.

astro-ph.SR↗

arXiv2016

Light Curve Analysis of GSC 2750-0054 and GSC 03208-02644

We present the first photometric analysis for the newly discovered eclipsing binary systems of Algole-type GSC 2750-0054 and GSC 03208-02644. Our analysis was carried out by means of the most recent version of Wilson Devinney (WD) code, which applies the model atmosphere by Kurucz (1993) with prescription in pass band for the radiative treatment. The accepted light curve solutions reveal absolute physical parameters and the spectral classifications for the components are adopted. Distance to each system was calculated based on the parameters of the accepted photometric solutions. Comparison with the evolutionary models are presented.

astro-ph.SR↗

arXiv2015

Approximate Solution to the Fractional Second Type Lane-Emden Equation

The spherical isothermal Lane-Emden equation is a second order non-linear differential equation that model many configurations in astrophysics. In the present paper and based on the fractal index technique and the series expansion, the fractional lane-Emden equation involving modified Riemann-Liouville derivative is solved. The results indicate that, the series converges for the radius range with fractional parameter spreads over a wide range of the fractional parameter . Comparison with the numerical solution revealed a good agreement with a maximum relative error 0.05.

astro-ph.SR↗

arXiv2015

Kinematics and Velocity Ellipsoid of the Solar Neighborhood White Dwarfs

To determine the velocity ellipsoid of the solar neighborhood white dwarfs, we use the space velocity components of stars. Two samples of white dwarfs are used, 20 pc and 25 pc samples. Beside the two main samples, the solar velocity and velocity dispersions are calculated for the four subsamples, namely DA, non - DA, hot and cool white dwarfs. Comparison between the results of 20 pc sample and those of 25 pc sample gives good agreement, while the comparison between the other subsamples gives bad agreement. Dependence of the velocity dispersions and solar velocity on the chemical composition and effective temperatures are discussed.

astro-ph.SR↗

arXiv2014

Detailed ROSAT X-ray Analysis of the AM Her Cataclysmic Variable VV Pup

VV Pup is typical system of AM Her stars, where the main accreting pole rotates in and out of view during the orbital cycle. In the present paper we present ROSAT data analysis for the magnetic cataclysmic variable VV Pup. We obtained the X-ray light curves of VV Pup in high state, the PSPC count rate 0.1-2.0 keV is plotted as a function of time with bins of 10 sec and the count rate is folded over the orbital period of 100.4 min with bin size of 100 sec for individual observations. We calculate the mean best-fit PSPC spectrum, with a three-component spectral fit including a soft X-ray blackbody, hard X-ray bremsstrahlung, and Gaussian line covers the phase intervals, for a bright phase (phi_orb=0.9-1.1), the dip data (phi_orb=0.18-0.7), the egress from the dip (phi_orb=0.7-0.8), the phase interval phi = 0.1-0.18 and the mean best-fit spectrum for all data (phi_orb=0.0-1.0). We calculate spectral parameters, the hardness ratios, count rate and total integrated black body flux.

astro-ph.SR↗