Journal or Publication Title:

Բյուրականի աստղադիտարանի հաղորդումներ: Երևանի աստղադիտարանի բյուլետեն = Сообщения Бюраканской обсерватории. Бюллетень ереванской Астрономической обсерватории = Contributions from the Burakan observatory. Bulletin of the Erevan astronomical observatory

Date of publication:

2021

Volume:

68

Number:

2

ISSN:

2579-2276

Coverage:

509-514

Abstract:

A nonlinear Volterra integral equation of the second kind is used instead of conventional Lane-Emden differential equation to represent an alternative approach to finding exact solutions and analytical approximations to solutions of the Lane-Emden equation for classical polytropic models. This approach enables us to reproduce the well - known Lane- Emden (or, just Emden) functions for polytropic indices n=0,1,5 directly or by making use of the Laplace transform, and, being combined with some heuristic reasonings, derive analytical approximations to exact solutions for n = 1.5, 2 and ∞ in closed forms. The proximity of all suggested analytical approximations to the exact solutions are evaluated with the use of the mean square error estimator. Standard deviations are found to be of 10−3 by the order of magnitude. The approximating function of the isothermal density distribution enables us to calculate a theoretical rotation curve that reproduces main features of rotation curves of a set of spiral galaxies. Detailed mathematical calculations will be introduced in an extended paper which is under preparation.

Format:

pdf

Identifier:

oai:arar.sci.am:296477

Language:

en

General note:

Communications of the Byurakan Astrophysical Observatory (ComBAO) is a peer-reviewed scientific journal, which publishes research in observational and theoretical astronomy/astrophysics and presents recent advances in these fields. It is being published by the NAS RA V. Ambartsumian Byurakan Astrophysical Observatory (BAO) in English in electronic form. The journal publishes original papers, review papers, brief reports, book reviews, special communications, observational and theoretical results in various fields of astronomy and related sciences, and some editorial notes, including anniversaries and obituaries. Under the heading “Legacy”, the renewed magazine will republish some old articles of high value in English. The heading “Guest articles” will bring to the attention of readers the articles of researchers who are not employees of BAO. ComBAO was founded in 1946 and regularly published in 1946-1990. However, the publication was interrupted because of the economic situation after the disintegration of the Soviet Union in 1991.

Location of original object:

ՀՀ ԳԱԱ Հիմնարար գիտական գրադարան