WR 16

Last updated
WR 16
Observation data
Epoch J2000       Equinox J2000
Constellation Carina [1]
Right ascension 09h 54m 52.9034s [2]
Declination +57° 43′ 38.2746″ [2]
Apparent magnitude  (V)8.36 [3]
Characteristics
Evolutionary stage Wolf-Rayet [4]
Spectral type WN8h [4]
Variable type WR [5] , ellipsoidal [6]
Astrometry
Proper motion (μ)RA: −9.458 [2] mas/yr
Dec.: +5.054 [2] mas/yr
Parallax (π)0.438±0.0168  mas [2]
Distance 7,400 ± 300  ly
(2,280 ± 90  pc)
Absolute magnitude  (MV)−5.6 [7]
Details
Mass 19 [8]   M☉
Radius 11.56 [8]   R☉
Luminosity 525,000 [8]   L☉
Temperature 44,700 [8]   K
Other designations
Hen 3-342, V396 Carinae, HD 86161, HIP 48617, SAO 237491 [9]
Database references
SIMBAD data

WR 16 (HD 86161) is a Wolf-Rayet star located in the constellation Carina. It is a massive, luminous, and evolved star in a late stage of evolution, surrounded by a complex nebula formed by its strong stellar winds and past mass ejections. WR 16 is classified as a runaway star due to its high velocity through the interstellar medium. [4]

Contents

Physical characteristics

A light curve for WR 16, plotted from TESS data WR16LightCurve.png
A light curve for WR 16, plotted from TESS data

WR 16 is classified as a WN8h star, [4] indicating a hydrogen-rich Wolf-Rayet star dominated by nitrogen emission lines. [11] Its effective temperature of over 40,000  K [8] is hotter than the Sun's typical value of 5,772 K, [12] but cooler than many other WR stars. [8]

WR 16 is a rotating ellipsoidal variable, meaning its brightness and shape change slightly due to rotation. [6]

Runaway status

Motion measurements from the Gaia satellite show that WR 16 moves at about 61 km/s relative to its local interstellar medium, qualifying it as a runaway star. This rapid motion influences the shape of its surrounding nebula. [4]

Nebular structure

WR 16 is surrounded by a bubble-like nebula formed by material ejected in previous evolutionary stages and shaped by its strong stellar winds. Observations reveal a round, bubble-shaped nebula visible in optical and infrared wavelengths. Multiple rings surround the star, likely from episodic mass ejections during its earlier Luminous Blue Variable (LBV) phase. Ionized hydrogen (H II regions) and nitrogen-enriched gas are present, indicating processed stellar material. [4]

Bow shock

Due to its high velocity, WR 16 creates a bow shock—a curved front where its stellar wind collides with the interstellar medium, compressing gas and dust. Radio and infrared imaging confirms the bow shock’s presence. [13] [4]

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific . 99 (617): 695. Bibcode:1987PASP...99..695R. doi: 10.1086/132034 . Constellation record for this object at VizieR.
  2. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  3. ↑ Zacharias, N.; Finch, C. T.; Girard, T. M.; Henden, A.; Bartlett, J. L.; Monet, D. G.; Zacharias, M. I. (2012). "VizieR Online Data Catalog: UCAC4 Catalogue (Zacharias+, 2012)". Vizier Online Data Catalog. Bibcode:2012yCat.1322....0Z.
  4. 1 2 3 4 5 6 7 Cichowolski, S; Duronea, N U; Suad, L A; et al. (June 2020). "The ISM local to the runaway star WR16". Monthly Notices of the Royal Astronomical Society. 495 (1): 417–427. Bibcode:2020MNRAS.495..417C. doi: 10.1093/mnras/staa1153 .
  5. ↑ Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085.
  6. 1 2 "V0396 Car". The International Variable Star Index. AAVSO. Retrieved 2 July 2025.
  7. ↑ Rate, Gemma; Crowther, Paul A. (2020). "Unlocking Galactic Wolf-Rayet stars with Gaia DR2 - I. Distances and absolute magnitudes". Monthly Notices of the Royal Astronomical Society. 493 (1): 1512. arXiv: 1912.10125 . Bibcode:2020MNRAS.493.1512R. doi: 10.1093/mnras/stz3614 .
  8. 1 2 3 4 5 6 Hamann, W. -R.; Gräfener, G.; Liermann, A.; Hainich, R.; Sander, A. A. C.; Shenar, T.; Ramachandran, V.; Todt, H.; Oskinova, L. M. (2019). "The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters". Astronomy and Astrophysics. 625. arXiv: 1904.04687 . Bibcode:2019A&A...625A..57H. doi:10.1051/0004-6361/201834850.
  9. ↑ "WR 16". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2025-07-17.
  10. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 2 July 2025.
  11. ↑ Niemela, V.; Gamen, R.; Morrell, N. (2001). "Long term optical spectroscopy of HD 86161 (WR 16)". Eta Carinae and Other Mysterious Stars: The Hidden Opportunities of Emission Spectroscopy. 242: 199. Bibcode: 2001ASPC..242..199N .
  12. ↑ Prša, Andrej; Harmanec, Petr; Torres, Guillermo; Mamajek, Eric; Asplund, Martin; Capitaine, Nicole; Christensen-Dalsgaard, Jørgen; Depagne, Éric; Haberreiter, Margit; Hekker, Saskia; Hilton, James; Kopp, Greg; Kostov, Veselin; Kurtz, Donald W.; Laskar, Jacques; Mason, Brian D.; Milone, Eugene F.; Montgomery, Michele; Richards, Mercedes; Schmutz, Werner; Schou, Jesper; Stewart, Susan G. (2016). "Nominal Values for Selected Solar and Planetary Quantities: IAU 2015 Resolution B3". The Astronomical Journal. 152 (2): 41. arXiv: 1605.09788 . Bibcode:2016AJ....152...41P. doi: 10.3847/0004-6256/152/2/41 . hdl:1885/108637. S2CID   55319250.
  13. ↑ Duronea, N. U.; Arnal, E. M.; Bronfman, L. (2013). "Carbon monoxide in the environs of the star WR 16". Astronomy and Astrophysics. 551: A71. arXiv: 1212.1335 . Bibcode:2013A&A...551A..71D. doi:10.1051/0004-6361/201219816.
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