MNRAS-2017-Reindl-L51-5.pdf (588.85 kB)
Breaking news from the HST: the central star of the Stingray Nebula is now returning towards the AGB
journal contribution
posted on 2016-11-18, 14:38 authored by Nicole Reindl, T. Rauch, M. M. M. Bertolami, H. Todt, K. WernerSAO 244567 is a rare example of a star that allows us to witness stellar evolution in real time. Between 1971 and 1990, it changed from a B-type star into the hot central star of the Stingray Nebula. This observed rapid heating has been a mystery for decades, since it is in strong contradiction with the low mass of the star and canonical post-asymptotic giant branch (AGB) evolution. We speculated that SAO 244567 might have suffered from a late thermal pulse (LTP) and obtained new observations with Hubble Space Telescope (HST)/COS to follow the evolution of the surface properties of SAO 244567 and to verify the LTP hypothesis. Our non-LTE spectral analysis reveals that the star cooled significantly since 2002 and that its envelope is now expanding. Therefore, we conclude that SAO 244567 is currently on its way back towards the AGB, which strongly supports the LTP hypothesis. A comparison with state-of-the-art LTP evolutionary calculations shows that these models cannot fully reproduce the evolution of all surface parameters simultaneously, pointing out possible shortcomings of stellar evolution models. Thereby, SAO 244567 keeps on challenging stellar evolution theory and we highly encourage further investigations.
Funding
NR is supported by a Leverhulme Trust Research Project Grant. NR was and TR is supported by the German Aerospace Center (DLR, grant 50 OR 1507). M3B is partially supported by ANPCyT through grant PICT-2014-2708 and by a Return Fellowship from the Alexander von Humboldt Foundation. We thank P. Chayer for reporting to us their results before publication and A. Istrate and M. Parthasarathy for helpful discussions and comments. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained 2015−08−09 at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 13708. The TMAD service (http://astro-uni-tuebingen.de/TMAD) used to compile atomic data and the TIRO service (http://astro-uni-tuebingen.de/TIRO) used to calculate opacities for this paper were constructed as part of the activities of the German Astrophysical Virtual Observatory. This research has made use of NASA’s Astrophysics Data System, the VizieR catalogue access tool and the SIMBAD data base operated at CDS, Strasbourg, France.
History
Citation
Monthly Notices of the Royal Astronomical Society: Letters, (January 01, 2017) 464 (1): L51-L55.Author affiliation
/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and AstronomyVersion
- VoR (Version of Record)