The puzzling high velocity G5 supergiant star HD 179821: new insight from Gaia DR2 data

  • M. ParthasarathyEmail author
  • G. Jasniewicz
  • F. Thěvenin
Original Article


HD 179821 is classified as G5 Ia star. From the IRAS colors and spectral energy distributions it was classified as a post-AGB star. But some studies classify it as a massive (30 to \(19~\mbox{M}_{\odot}\)) post-red supergiant evolving to become a Type II supernova. Its mass and evolutionary status remained a hotly debated question even after several detailed spectroscopic studies as the distance was not known. We use the parallax of HD 179821 from the second Gaia data release, and deduce its distance \(2959 \pm 409~\mbox{pc}\) and its absolute magnitude \(\mbox{MV} = -5.7 \pm 0.3\). Using the absolute magnitude determined in this paper, we show that HD 179821 fits very well with post-AGB tracks in the \(H-R\) diagram. Our results clearly confirm that HD 179821 is a post-AGB star of mass in the range of 0.70 to 0.75 solar mass. It is not a \(30~\mbox{M}_{\odot}\) red supergiant. The progenitor mass of this post-AGB star may be in the range of \(4~\mbox{M}_{\odot}\) but may be a bit more.


Stars: AGB and post-AGB Stars: individual: HD179821 Stars: distances Stars: evolution 



This study has made use of the SIMBAD database, the VizieR catalogue access tool and of NASA’s Astrophysics Data System, operated at CDS, Strasbourg, France. The authors are grateful to Olivia Mancuso for her review of English phrasing and grammar in this article.


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© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.Indian Institute of AstrophysicsBangaloreIndia
  2. 2.UMR 5299 LUPM CNRS/Universitè MontpellierMontpellier cedex 05France
  3. 3.Observatoire de la Côte d’AzurUMR 6202 Cassiopée/CNRSNice cedex 4France

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