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 |
| Characteristics | |
| Evolutionary stage | Wolf-Rayet |
| Spectral type | WN8h |
| Variable type | WR |
| 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) |
| Details | |
| Radius | 12.3 ± 0.5[3] R☉ |
| Luminosity | 477,000 ± 11,000[3] L☉ |
| Temperature | 41,700 ± 1,000[3] K |
| Other designations | |
| HD 86161, SAO 237491, HIP 48617, Hen 3-342 | |
| 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]
Physical characteristics
WR 16 is classified as a WN8h star,[4] indicating a hydrogen-rich Wolf-Rayet star dominated by nitrogen emission lines.[6] Its effective temperature of over 40,000 K[3] is hotter than the Sun's typical value of 5,772±0.8 K,[7] but cooler than many other WR stars.
WR 16 is a rotating ellipsoidal variable, meaning its brightness and shape change slightly due to rotation.[8]
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.[9][4]
Observations
Imaging and spectroscopy
WR 16 has been extensively observed across multiple wavelengths:
- Optical and infrared imaging using hydrogen-alpha (Hα) and broadband filters to reveal gas and dust structures.
- Molecular line observations (CO and HCO⁺) using submillimeter telescopes including ASTE and NANTEN, mapping the nebula's molecular gas.
- Radio continuum observations at frequencies near 1.4 GHz and 943.5 MHz detected ionized gas and thermal emission from the nebula.
- X-ray observations with XMM-Newton showed no diffuse X-ray emission from the nebula, which is unusual for a WR nebula.
Instruments used
- Planewave CDK24 telescope and QHY 600M Pro camera (Chile)
- ASTE 10-meter submillimeter telescope (Chile)
- Australia Telescope Compact Array (ATCA)[10]
- WISE and Herschel infrared space telescopes
- Gaia satellite for parallax and proper motion measurements
- XMM-Newton X-ray observatory[11]
References
- ^ 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.
- ^ a b c d e 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.
- ^ a b c d Herald, J. E.; Hillier, D. J.; Schulte-Ladbeck, R. E. (2001). "Tailored Analyses of the WN 8 Stars WR 40 and WR 16". The Astrophysical Journal. 548 (2): 932–952. Bibcode:2001ApJ...548..932H. doi:10.1086/319007.
- ^ a b c d e 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.
- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 2 July 2025.
- ^ 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.
- ^ 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.
- ^ "V0396 Car". The International Variable Star Index. AAVSO. Retrieved 2 July 2025.
- ^ 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.
- ^ Bradley, A. C.; Filipović, M. D.; Smeaton, Z. J.; Sano, H.; Fukui, Y.; Bordiu, C.; Cichowolski, S.; Tothill, N. F. H.; Alsaberi, R. Z. E.; Bufano, F.; Dai, S.; Gordon, Y. A.; Hopkins, A. M.; Jarrett, T. H.; Koribalski, B. S.; Lazarević, S.; Riseley, C. J.; Rowell, G.; Sasaki, M.; Urošević, D.; Vernstrom, T. (2025). "Evolutionary Map of the Universe: Detection and Analysis of the Shell Surrounding the Runaway Wolf-Rayet Star WR16". arXiv:2506.23588v1 [astro-ph.SR].
- ^ Toalá, J. A.; Guerrero, M. A. (2013). "Absence of hot gas within the Wolf-Rayet bubble around WR 16". Astronomy & Astrophysics. 559: A52. arXiv:1309.0236. Bibcode:2013A&A...559A..52T. doi:10.1051/0004-6361/201322286.