<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0185-1101</journal-id>
<journal-title><![CDATA[Revista mexicana de astronomía y astrofísica]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. mex. astron. astrofis]]></abbrev-journal-title>
<issn>0185-1101</issn>
<publisher>
<publisher-name><![CDATA[Universidad Nacional Autónoma de México, Instituto de Astronomía]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0185-11012017000200008</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Approximate Analytical Solutions to the Relativistic Isothermal Gas Spheres]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Saad]]></surname>
<given-names><![CDATA[A. S.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
<xref ref-type="aff" rid="Aaf"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Nouh]]></surname>
<given-names><![CDATA[M. I.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
<xref ref-type="aff" rid="Aaf"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Shaker]]></surname>
<given-names><![CDATA[A. A.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Kamel]]></surname>
<given-names><![CDATA[T. M.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,National Research Institute of Astronomy and Geophysics Department of Astronomy ]]></institution>
<addr-line><![CDATA[Cairo ]]></addr-line>
<country>Egypt</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Qassim University Preparatory Year Department of Mathematics]]></institution>
<addr-line><![CDATA[Buraidah ]]></addr-line>
<country>KSA</country>
</aff>
<aff id="Af3">
<institution><![CDATA[,Northern Border University College of Science Department of Physics]]></institution>
<addr-line><![CDATA[Arar ]]></addr-line>
<country>KSA</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>00</month>
<year>2017</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>00</month>
<year>2017</year>
</pub-date>
<volume>53</volume>
<numero>2</numero>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0185-11012017000200008&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0185-11012017000200008&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0185-11012017000200008&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[ABSTRACT In this paper we introduce a novel analytical solution to TolmanOppenheimer-Volkoff (TOV) equation, which is ultimately a hydrostatic equilibrium equation derived from general relativity in the framework of relativistic isothermal spheres. To improve the convergence radii of the obtained series solutions, a combination of an Euler-Abel transformation and a Pad´e approximation has been done. The solutions are given in the &#958;-&#952; and &#958;-&#957; phase planes taking into account the general relativistic effects &#963; = 0.1, 0.2 and 0.3. A comparison between the results obtained by the suggested approach and the numerical one indicates a good agreement, with a maximum relative error of order 10&#8722;3, which establishes the validity and accuracy of the method. The proposed procedure accelerated the power series solution about ten times that of the traditional one. An application to a neutron star is presented.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[RESUMEN Presentamos una solución analítica novedosa para la ecuación de Tolman-Oppenheimer-Volkoff (TOV), que resulta ser una ecuación de equilibrio hidrostático derivada de la relatividad general, dentro del marco de las esferas isotérmicas relativistas. Para mejorar los radios de convergencia de las soluciones en serie obtenidas se han combinado las aproximaciones de Euler-Abel y Padé. Las soluciones se proporcionan en los planos de fase &#958;-&#952; y &#958;-&#957;, tomando en cuenta efectos de relatividad general con &#963; = 0.1, 0.2, y 0.3. La comparación entre los resultados que obtenemos y las soluciones numéricas indican una buena concordancia, dentro de un error máximo relativo del orden de 10&#8722;3, con lo cual queda establecida la validez y la precisión del método. El procedimiento propuesto acelera la solución en series de potencia por un factor de 10, respecto al procedimiento tradicional. Se presenta una aplicación a una estrella neutrón.]]></p></abstract>
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<kwd lng="en"><![CDATA[equation of state]]></kwd>
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<kwd lng="en"><![CDATA[analytical]]></kwd>
<kwd lng="en"><![CDATA[stars]]></kwd>
<kwd lng="en"><![CDATA[neutrón]]></kwd>
<kwd lng="en"><![CDATA[relativistic processes]]></kwd>
</kwd-group>
</article-meta>
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