<?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>S0185-11012024000100177</article-id>
<article-id pub-id-type="doi">10.22201/ia.01851101p.2024.60.01.13</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[CCD Photometry of Trapezia Stars I]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Ruelas-Mayorga]]></surname>
<given-names><![CDATA[A.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Sánchez]]></surname>
<given-names><![CDATA[L. J.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Páez-Amador]]></surname>
<given-names><![CDATA[A.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Segura-Montero]]></surname>
<given-names><![CDATA[O.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Nigoche-Netro]]></surname>
<given-names><![CDATA[A.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad Nacional Autónoma de México Instituto de Astronomía ]]></institution>
<addr-line><![CDATA[ Ciudad de México]]></addr-line>
<country>México</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Universidad de Guadalajara Instituto de Astronomía y Meteorología ]]></institution>
<addr-line><![CDATA[Guadalajara Jal.]]></addr-line>
<country>México</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>00</month>
<year>2024</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>00</month>
<year>2024</year>
</pub-date>
<volume>60</volume>
<numero>1</numero>
<fpage>177</fpage>
<lpage>197</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0185-11012024000100177&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0185-11012024000100177&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0185-11012024000100177&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[ABSTRACT We present photometric CCD observations of stars in four stellar trapezia ADS 15184, ADS 4728, ADS 2843, and ADS 16795. This study is performed on images obtained at the Observatorio Astronómico Nacional (OAN) at San Pedro Mártir, Baja California, México. In this work we utilise aperture photometry to measure the U, B, V, R and I magnitudes of some of the stars in these dynamically unstable stellar clusters (trapezia). Using the Q = (U - B) - 0.72(B - V) parameter we obtain the spectral type of the studied stars as well as their distance to the Sun and their reddening. Slight differences between the Q-derived spectral types and those listed in SIMBAD might be due to a value different from 0.72 for the slope of the reddening line on the two-colour diagram.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[RESUMEN  Presentamos fotometría CCD de las estrellas en cuatro trapecios estelares ADS 15184, ADS 728, ADS 2843, y ADS 16795. El estudio se hace a partir de imágenes tomadas en el Observatorio Astronómico Nacional de San Pedro Mártir (OAN), Baja California, México. El presente trabajo utiliza la técnica de fotometría de apertura para medir las magnitudes U, B, V, R e I de algunas estrellas en estos cúmulos abiertos dinámicamente inestables (trapecios). Usando el parámetro Q = (U - B) - 0.72(B - V) se obtuvo el tipo espectral de las estrellas estudiadas, también se derivaron sus distancias al Sol y sus enrojecimientos. Ligeras diferencias en los tipos espectrales derivados a partir del parámetro Q con los listados en SIMBAD, podrían deberse a un valor diferente de 0.72 de la pendiente de la línea de enrojecimiento en el diagrama de dos colores.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Galaxy: stellar content]]></kwd>
<kwd lng="en"><![CDATA[open clusters and associations: individual]]></kwd>
<kwd lng="en"><![CDATA[ADS15184]]></kwd>
<kwd lng="en"><![CDATA[ADS728]]></kwd>
<kwd lng="en"><![CDATA[ADS2843]]></kwd>
<kwd lng="en"><![CDATA[ADS16795]]></kwd>
<kwd lng="en"><![CDATA[techniques: photometry]]></kwd>
</kwd-group>
</article-meta>
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