WR 156 is a young massive and luminous Wolf–Rayet star in the constellation of Cepheus. Although it shows a WR spectrum, it is thought to be a young star still fusing hydrogen in its core.

Distance

WR 156 has a Hipparcos parallax of 3.16" indicating a distance of about a thousand light years, although with a fairly large margin of error. Other studies indicate that it is much more distant based on a very high luminosity and faint apparent magnitude.[6] The Gaia DR1 parallax is 0.07". The margin of error is larger than the measured parallax, but still the indication is for a very large distance.[7] In Gaia Data Release 2, the parallax is given as 0.2090±0.0251 mas but with a marker that the result may be unreliable.[4] In the Gaia Early Release 3, the solution was adjusted to 0.2749±0.0125 mas, still with significant astrometric noise excess.[5]

Physical properties

WR 156 has a WR spectrum on the nitrogen sequence, indicating strong emission of helium and nitrogen, but it also shows features of hydrogen. Therefore, it is given a spectral type of WN8h. Its outer layers are calculated to contain 30% hydrogen, one of the highest levels for any galactic Wolf Rayet star.[8]

WR 156 has a low temperature and slow stellar wind by Wolf Rayet standards, only 39,800 K and 660 km/s respectively. The wind is very dense, with total mass loss of more than 1/100,000 M☉/year.[6]

WR 156 is a young hydrogen-rich star, still burning hydrogen in its core but sufficiently luminous to have convected up nitrogen and helium fusion products to its surface. It shows 27% hydrogen at its surface.[6] It is estimated to have had an initial mass of 50 M☉ several million years ago.[8]

References

  1. ^ a b Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862. ISBN 0333750888.
  3. ^ Maryeva, Olga (2016). "The study of massive stars with 50 Msun initial mass at different evolutionary stages". arXiv:1612.01191 [astro-ph.SR].
  4. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  5. ^ a b Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  6. ^ a b c d e f g h Sota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J.; Oskinova, L. M. (2019). "The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters". Astronomy & Astrophysics. A57: 625. arXiv:1904.04687. Bibcode:2019A&A...625A..57H. doi:10.1051/0004-6361/201834850. S2CID 104292503.
  7. ^ Gaia Collaboration (2016). "VizieR Online Data Catalog: Gaia DR1 (Gaia Collaboration, 2016)". VizieR On-line Data Catalog: I/337. Originally Published in: Astron. Astrophys. 1337. Bibcode:2016yCat.1337....0G. doi:10.26093/cds/vizier.1337.
  8. ^ a b Maryeva, O. V.; Afanasiev, V. L.; Panchuk, V. E. (2013). "Study of the late nitrogen-sequence Galactic Wolf-Rayet star WR156. Spectropolarimetry and modeling". New Astronomy. 25: 27–31. Bibcode:2013NewA...25...27M. doi:10.1016/j.newast.2013.03.015.
Allikas: https://en.wikipedia.org/wiki/WR_156
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