<?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>S0185-11012016000200347</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Variability of the emission line fluxes and ratios of HH 1/2]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Raga]]></surname>
<given-names><![CDATA[A. C.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Reipurth]]></surname>
<given-names><![CDATA[B.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Castellanos-Ramírez]]></surname>
<given-names><![CDATA[A.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Bally]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad Nacional Autónoma de México Instituto de Ciencias Nucleares ]]></institution>
<addr-line><![CDATA[ Ciudad de México]]></addr-line>
<country>Mexico</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Univ. of Hawaii Institute for Astronomy ]]></institution>
<addr-line><![CDATA[Hilo ]]></addr-line>
<country>USA</country>
</aff>
<aff id="Af3">
<institution><![CDATA[,Univ. of Colorado Center for Astrophysics and Space Astronomy ]]></institution>
<addr-line><![CDATA[ Colorado]]></addr-line>
<country>USA</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>00</month>
<year>2016</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>00</month>
<year>2016</year>
</pub-date>
<volume>52</volume>
<numero>2</numero>
<fpage>347</fpage>
<lpage>355</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0185-11012016000200347&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0185-11012016000200347&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0185-11012016000200347&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract: We compare spectrophotometric data of HH 1 and 2 obtained in 1978 (by Brugel et al. 1981a) with the emission line fluxes from calibrated Hubble Space Telescope (HST) images obtained in 1994 and 2014. This comparison shows that the emission line ratios of these objects have remained surprisingly invariant during the past 36 years. On the other hand, the line intensities have indeed changed, with HH 2 brightening by a factor of &#8776; 4 and HH 1 becoming &#8776; 30% fainter. These results would be consistent with HH 1 and 2 being leading working surfaces of heavy jets travelling into an environment of decreasing (for HH 1) or increasing (HH 2) densities.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Resumen: Comparamos datos espectrofotométricos obtenidos en 1978 (por Brugel et al. 1981a) con los flujos de líneas de emisión de imágenes calibradas obtenidas con el Hubble Space Telescope (HST) en 1994 y 2014. Esta comparación muestra que los cocientes de líneas de emisión de estos objetos se han mantenido sorprendentemente invariantes durante los ultimos 36 años. Por otro lado, las intensidades de las líneas sí han cambiado, y muestran un incremento por un factor de &#8776; 4 para HH 2, y un decremento de &#8776; 30% para HH 1. Estos resultados apoyan la idea de que HH 1 y 2 son cabezas de jets densos, viajando en un medio ambiente con densidad decreciente (para HH 1) o creciente (para HH 2).]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Herbig-Haro objects]]></kwd>
<kwd lng="en"><![CDATA[ISM: individual objects (HH1/2)]]></kwd>
<kwd lng="en"><![CDATA[ISM: jets and outflows]]></kwd>
<kwd lng="en"><![CDATA[shock waves]]></kwd>
<kwd lng="en"><![CDATA[stars: formation]]></kwd>
<kwd lng="en"><![CDATA[stars: winds, out-flows]]></kwd>
</kwd-group>
</article-meta>
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