<?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>S0185-11012020000200193</article-id>
<article-id pub-id-type="doi">10.22201/ia.01851101p.2020.56.02.02</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[A search for pulsation in twenty-one white dwarfs]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Paunzen]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Handler]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Janík]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Zemanová]]></surname>
<given-names><![CDATA[Z.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Rode-Paunzen]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[O&#8217;Brien]]></surname>
<given-names><![CDATA[M. S.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Watson]]></surname>
<given-names><![CDATA[T. K.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Dró&#380;d&#380;]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Masaryk University Department of Theoretical Physics and Astrophysics ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Czech Republic</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Nicolaus Copernicus Astronomical Center  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Poland</country>
</aff>
<aff id="Af3">
<institution><![CDATA[,Uherske Hradí&#353;t&#283; High school ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Czech Republic</country>
</aff>
<aff id="Af4">
<institution><![CDATA[,Nicolaus Copernicus Astronomical Center  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Poland</country>
</aff>
<aff id="Af5">
<institution><![CDATA[,Space Telescope Science Institute  ]]></institution>
<addr-line><![CDATA[Baltimore ]]></addr-line>
<country>USA</country>
</aff>
<aff id="Af6">
<institution><![CDATA[,Southwestern University Information Technology ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>USA</country>
</aff>
<aff id="Af7">
<institution><![CDATA[,Mt. Suhora Observatory  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Poland</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>00</month>
<year>2020</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>00</month>
<year>2020</year>
</pub-date>
<volume>56</volume>
<numero>2</numero>
<fpage>193</fpage>
<lpage>199</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0185-11012020000200193&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0185-11012020000200193&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0185-11012020000200193&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[ABSTRACT Well-defined astrophysical constraints of white dwarfs (WDs), such as on the presence or absence of pulsational variability, are very much needed to refine and develop current models. Because these stars are rather faint and variability periods are mostly below one hour, only a very limited amount of space-based data is currently available for these objects. We present about 68 hours of high-quality ground-based photometric time-series data for twenty-one WDs acquired at five different observatories. No new pulsators were detected but the derived upper limits of variability, which are typically on the order of only a few mmags, provide important input for pulsation models.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[RESUMEN Es muy necesario contar con cotas astrofísicas bien definidas para los parámetros de las enanas blancas (WD) con el objeto de mejorar los modelos actuales. Dado que estas estrellas son débiles y tienen períodos de variabilidad de menos de una hora, actualmente solo contamos con datos muy limitados basados en observaciones espaciales. Presentamos´ 68 horas de datos fotométricos de alta calidad obtenidos en cinco obsevatorios terrestres para 21 enanas blancas. No se encontraron pulsadores nuevos, pero los límites superiores para la variabilidad que determinamos, del orden de unas cuantas mmags, son importantes para la construcción de modelos de pulsación.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[white dwarfs]]></kwd>
</kwd-group>
</article-meta>
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