<p>A time series of high-resolution spectra in the optical wavelength region was used to examine the variability of physical parameters of the early-stage post-AGB star IRAS 22272<InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12036_2024_10037_Article_IEq3.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="TEX">\(+\)</EquationSource> <EquationSource Format="MATHML"><math> <mo>+</mo> </math></EquationSource> </InlineEquation>5435. Excitation balance analysis for a sample of iron (Fe), cerium (Ce), and neodymium (Nd) lines confirms effective temperature changes from about <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12036_2024_10037_Article_IEq4.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="78" /> </InlineMediaObject> <EquationSource Format="TEX">\(5100\pm 150\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>5100</mn> <mo>±</mo> <mn>150</mn> </mrow> </math></EquationSource> </InlineEquation> to <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12036_2024_10037_Article_IEq5.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="78" /> </InlineMediaObject> <EquationSource Format="TEX">\(5750\pm 100\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>5750</mn> <mo>±</mo> <mn>100</mn> </mrow> </math></EquationSource> </InlineEquation>&#xa0;K during the 132-day pulsation cycle. Using the method of ionization balance, we observed a minor change in surface gravity between <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12036_2024_10037_Article_IEq6.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="76" /> </InlineMediaObject> <EquationSource Format="TEX">\(\log g= 0.5\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>log</mo> <mi>g</mi> <mo>=</mo> <mn>0.5</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12036_2024_10037_Article_IEq7.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="64" /> </InlineMediaObject> <EquationSource Format="TEX">\(0.7\pm 0.3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0.7</mn> <mo>±</mo> <mn>0.3</mn> </mrow> </math></EquationSource> </InlineEquation> (cgs). The microturbulent velocity does not change within the uncertainty limits, <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12036_2024_10037_Article_IEq8.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="99" /> </InlineMediaObject> <EquationSource Format="TEX">\(\xi _t=4.5\pm 0.5\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>ξ</mi> <mi>t</mi> </msub> <mo>=</mo> <mn>4.5</mn> <mo>±</mo> <mn>0.5</mn> </mrow> </math></EquationSource> </InlineEquation> km s<InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12036_2024_10037_Article_IEq9.gif" Format="GIF" Height="11" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(^{-1}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </mmultiscripts> </math></EquationSource> </InlineEquation>. Large macroturbulence in the range of 20–25 km s<InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12036_2024_10037_Article_IEq10.gif" Format="GIF" Height="11" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(^{-1}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </mmultiscripts> </math></EquationSource> </InlineEquation> was found. We observed variable intensity of the oxygen (O) infrared triplet at 7771-5 Å&#xa0; which is most likely due to changes in luminosity during the pulsation cycle.</p>

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Variability of physical parameters of IRAS 22272\(+\)5435 during the pulsation cycle

  • Laimons Začs,
  • Kārlis Puķītis

摘要

A time series of high-resolution spectra in the optical wavelength region was used to examine the variability of physical parameters of the early-stage post-AGB star IRAS 22272 \(+\) + 5435. Excitation balance analysis for a sample of iron (Fe), cerium (Ce), and neodymium (Nd) lines confirms effective temperature changes from about \(5100\pm 150\) 5100 ± 150 to \(5750\pm 100\) 5750 ± 100  K during the 132-day pulsation cycle. Using the method of ionization balance, we observed a minor change in surface gravity between \(\log g= 0.5\) log g = 0.5 and \(0.7\pm 0.3\) 0.7 ± 0.3 (cgs). The microturbulent velocity does not change within the uncertainty limits, \(\xi _t=4.5\pm 0.5\) ξ t = 4.5 ± 0.5 km s \(^{-1}\) - 1 . Large macroturbulence in the range of 20–25 km s \(^{-1}\) - 1 was found. We observed variable intensity of the oxygen (O) infrared triplet at 7771-5 Å  which is most likely due to changes in luminosity during the pulsation cycle.