<?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>S0185-11012025000100117</article-id>
<article-id pub-id-type="doi">10.22201/ia.01851101p.2025.61.01.09</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Long-Term Variability of Water Maser Emission in S128]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Lekht]]></surname>
<given-names><![CDATA[E. E.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Mendoza-Torres]]></surname>
<given-names><![CDATA[J. E.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Ashimbaeva]]></surname>
<given-names><![CDATA[N. T.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
<xref ref-type="aff" rid="Aaf"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Krasnov]]></surname>
<given-names><![CDATA[V. V.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Shoutenkov]]></surname>
<given-names><![CDATA[V. R.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Lomonosov Moscow State University Sternberg Astronomical Institute ]]></institution>
<addr-line><![CDATA[Moscow ]]></addr-line>
<country>Russia</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Instituto Nacional de Astrofísica, Óptica y Electrónica  ]]></institution>
<addr-line><![CDATA[Sta. María Tonantzintla Puebla]]></addr-line>
<country>México</country>
</aff>
<aff id="Af3">
<institution><![CDATA[,Russian Academy of Sciences Lebedev Physical Institute Astro Space Center]]></institution>
<addr-line><![CDATA[Moscow ]]></addr-line>
<country>Russia</country>
</aff>
<aff id="Af4">
<institution><![CDATA[,Russian Academy of Sciences Lebedev Physical Institute Pushchino Radio Astronomy Observatory]]></institution>
<addr-line><![CDATA[Pushchino ]]></addr-line>
<country>Russia</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>00</month>
<year>2025</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>00</month>
<year>2025</year>
</pub-date>
<volume>61</volume>
<numero>1</numero>
<fpage>117</fpage>
<lpage>122</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0185-11012025000100117&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0185-11012025000100117&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0185-11012025000100117&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract The evolution of the H2O maser emission at the S128 source during 1981-2024 is analyzed, based on long-term regular observations. The emission from -73 to -70 km/s corresponds mainly to source B, while that of velocities &lt; -76 km/s to source A. It was identified that in the time interval 2004-2006, the maser activity gradually shifted from source B to source A. The active phases of masers B and A lasted approximately 23 and 16 years, respectively. It is assumed that the common cause of the variability of the maser emission at both sources (A and B) can be shock waves that occur near the ionization front. When clouds collide, a disturbance propagates along the resulting ionization front, which leads to the appearance of shock waves. It is shown that the disturbance is spreading in the south-north direction. The star formation process occurs in the same direction.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Resumen Se analiza la evolución de la emisión maser de H2O en la fuente S128 durante 1981-2024, con base en su monitoreo regular. La emisión de -73 a -70 km/s proviene principalmente de la fuente B, mientras que la de &lt; -76 km/s de la fuente A. Se identifico que en el intervalo de tiempo 2004-2006, la actividad maser cambio gradualmente de la fuente B a la fuente A. Las fases activas de los maseres B y A duraron aproximadamente 23 y 16 años, respectivamente. Se supone que la causa común de la variabilidad de la emisión maser en ambas fuentes (A y B) puede ser ondas de choque, que ocurren cerca del frente de ionización. Cuando las nubes chocan, la perturbación se propaga a lo largo del frente de ionización resultante, que conduce a la aparición de ondas de choque. Se observa que la perturbación se está extendiendo en dirección sur-norte. El proceso de formación estelar ocurre en la misma dirección.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[clouds]]></kwd>
<kwd lng="en"><![CDATA[masers]]></kwd>
<kwd lng="en"><![CDATA[stars formation]]></kwd>
</kwd-group>
</article-meta>
</front><back>
<ref-list>
<ref id="B1">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Ashimbaeva]]></surname>
<given-names><![CDATA[N. T.]]></given-names>
</name>
<name>
<surname><![CDATA[Colom]]></surname>
<given-names><![CDATA[P.]]></given-names>
</name>
<name>
<surname><![CDATA[Lekht]]></surname>
<given-names><![CDATA[E. E.]]></given-names>
</name>
</person-group>
<source><![CDATA[ARep]]></source>
<year>2018</year>
<volume>62</volume>
<page-range>609</page-range></nlm-citation>
</ref>
<ref id="B2">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Ashimbaeva]]></surname>
<given-names><![CDATA[N. T.]]></given-names>
</name>
<name>
<surname><![CDATA[Krasnov]]></surname>
<given-names><![CDATA[V. V.]]></given-names>
</name>
<name>
<surname><![CDATA[Lekht]]></surname>
<given-names><![CDATA[E. E.]]></given-names>
</name>
</person-group>
<source><![CDATA[ARep]]></source>
<year>2020</year>
<volume>64</volume>
<page-range>15</page-range></nlm-citation>
</ref>
<ref id="B3">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Ashimbaeva]]></surname>
<given-names><![CDATA[N. T.]]></given-names>
</name>
<name>
<surname><![CDATA[Lekht]]></surname>
<given-names><![CDATA[E. E.]]></given-names>
</name>
<name>
<surname><![CDATA[Krasnov]]></surname>
<given-names><![CDATA[V. V.]]></given-names>
</name>
<name>
<surname><![CDATA[Tolmachev]]></surname>
<given-names><![CDATA[A. M.]]></given-names>
</name>
</person-group>
<source><![CDATA[ARep]]></source>
<year>2023</year>
<volume>67</volume>
<page-range>697</page-range></nlm-citation>
</ref>
<ref id="B4">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Berulis]]></surname>
<given-names><![CDATA[I. I.]]></given-names>
</name>
<name>
<surname><![CDATA[Lekht]]></surname>
<given-names><![CDATA[E. E.]]></given-names>
</name>
<name>
<surname><![CDATA[Mendoza-Torres]]></surname>
<given-names><![CDATA[J. E.]]></given-names>
</name>
</person-group>
<source><![CDATA[ARep]]></source>
<year>1995</year>
<volume>39</volume>
<page-range>411</page-range></nlm-citation>
</ref>
<ref id="B5">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Bohigas]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
<name>
<surname><![CDATA[Tapia]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
</person-group>
<source><![CDATA[AJ]]></source>
<year>2003</year>
<volume>126</volume>
<page-range>1861</page-range></nlm-citation>
</ref>
<ref id="B6">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Colom]]></surname>
<given-names><![CDATA[P.]]></given-names>
</name>
<name>
<surname><![CDATA[Ashimbaeva]]></surname>
<given-names><![CDATA[N. T.]]></given-names>
</name>
<name>
<surname><![CDATA[Lekht]]></surname>
<given-names><![CDATA[E. E.]]></given-names>
</name>
</person-group>
<source><![CDATA[ARep.]]></source>
<year>2019</year>
<volume>63</volume>
<page-range>814</page-range></nlm-citation>
</ref>
<ref id="B7">
<nlm-citation citation-type="book">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Elitzur]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
</person-group>
<source><![CDATA[Astronomical masers]]></source>
<year>1992</year>
<numero>170</numero>
<issue>170</issue>
<publisher-loc><![CDATA[Dorderecht ]]></publisher-loc>
<publisher-name><![CDATA[Kluwer]]></publisher-name>
</nlm-citation>
</ref>
<ref id="B8">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Haschick]]></surname>
<given-names><![CDATA[A. D.]]></given-names>
</name>
<name>
<surname><![CDATA[Ho]]></surname>
<given-names><![CDATA[P. T. P.]]></given-names>
</name>
</person-group>
<source><![CDATA[ApJ]]></source>
<year>1985</year>
<volume>292</volume>
<page-range>200</page-range></nlm-citation>
</ref>
<ref id="B9">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Ho]]></surname>
<given-names><![CDATA[P. T. P.]]></given-names>
</name>
<name>
<surname><![CDATA[Haschick]]></surname>
<given-names><![CDATA[A. D.]]></given-names>
</name>
<name>
<surname><![CDATA[Israel]]></surname>
<given-names><![CDATA[F. P.]]></given-names>
</name>
</person-group>
<source><![CDATA[ApJ]]></source>
<year>1981</year>
<volume>243</volume>
<page-range>526</page-range></nlm-citation>
</ref>
<ref id="B10">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Lekht]]></surname>
<given-names><![CDATA[E. E.]]></given-names>
</name>
<name>
<surname><![CDATA[Likhachev]]></surname>
<given-names><![CDATA[S. F.]]></given-names>
</name>
<name>
<surname><![CDATA[Sorochenko]]></surname>
<given-names><![CDATA[R. L.]]></given-names>
</name>
<name>
<surname><![CDATA[Strel&#8217;nitskii]]></surname>
<given-names><![CDATA[V. S.]]></given-names>
</name>
</person-group>
<source><![CDATA[ARep]]></source>
<year>1983</year>
<volume>37</volume>
<page-range>367</page-range></nlm-citation>
</ref>
<ref id="B11">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Lekht]]></surname>
<given-names><![CDATA[E. E.]]></given-names>
</name>
<name>
<surname><![CDATA[Mendoza-Torres]]></surname>
<given-names><![CDATA[J. E.]]></given-names>
</name>
<name>
<surname><![CDATA[Berulis]]></surname>
<given-names><![CDATA[I. I.]]></given-names>
</name>
</person-group>
<source><![CDATA[ARep]]></source>
<year>2002</year>
<volume>46</volume>
<page-range>57</page-range></nlm-citation>
</ref>
<ref id="B12">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Mampaso]]></surname>
<given-names><![CDATA[A.]]></given-names>
</name>
<name>
<surname><![CDATA[Gomez]]></surname>
<given-names><![CDATA[P.]]></given-names>
</name>
<name>
<surname><![CDATA[Sanchez-Magro]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
<name>
<surname><![CDATA[Selby]]></surname>
<given-names><![CDATA[M. J.]]></given-names>
</name>
</person-group>
<source><![CDATA[MNRAS]]></source>
<year>1984</year>
<volume>207</volume>
<page-range>465</page-range></nlm-citation>
</ref>
<ref id="B13">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Migenes]]></surname>
<given-names><![CDATA[V.]]></given-names>
</name>
<name>
<surname><![CDATA[Horiuchi]]></surname>
<given-names><![CDATA[S.]]></given-names>
</name>
<name>
<surname><![CDATA[Slysh]]></surname>
<given-names><![CDATA[V. I.]]></given-names>
</name>
</person-group>
<source><![CDATA[ApJ]]></source>
<year>1999</year>
<volume>123</volume>
<page-range>487</page-range></nlm-citation>
</ref>
<ref id="B14">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Richards]]></surname>
<given-names><![CDATA[A. M. S.]]></given-names>
</name>
<name>
<surname><![CDATA[Cohen]]></surname>
<given-names><![CDATA[R. J.]]></given-names>
</name>
<name>
<surname><![CDATA[Crocker]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
</person-group>
<source><![CDATA[ApSS]]></source>
<year>2005</year>
<volume>295</volume>
<page-range>19</page-range></nlm-citation>
</ref>
<ref id="B15">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wood]]></surname>
<given-names><![CDATA[D. O. S.]]></given-names>
</name>
<name>
<surname><![CDATA[Churchwell]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
</person-group>
<source><![CDATA[ApSC]]></source>
<year>1989</year>
<volume>69</volume>
<page-range>831</page-range></nlm-citation>
</ref>
<ref id="B16">
<nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wouterloot]]></surname>
<given-names><![CDATA[J. G. A.]]></given-names>
</name>
<name>
<surname><![CDATA[Brand]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
<name>
<surname><![CDATA[Henkel]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
</person-group>
<source><![CDATA[AA]]></source>
<year>1988</year>
<volume>191</volume>
<page-range>323</page-range></nlm-citation>
</ref>
</ref-list>
</back>
</article>
