An OH/IR star is an asymptotic giant branch (AGB) or a red supergiant or hypergiant (RSG or RHG) star that shows strong OH maser emission and is unusually bright at near-infrared wavelengths.
In the very late stages of AGB evolution, a star develops a super-wind with extreme mass loss. The gas in the stellar wind condenses as it cools away from the star, forming molecules such as water (H2O) and silicon monoxide (SiO). This can form grains of dust, mostly silicates, which obscure the star at shorter wavelengths, leading to a strong infrared source.[1] Hydroxyl (OH) radicals can be produced by photodissociation or collisional dissociation.[2]
H2O and OH can both be pumped to produce maser emission. OH masers in particular can give rise to a powerful maser action at 1612 MHz and this is regarded as a defining feature of the OH/IR stars. Many other AGB stars such as Mira variables show weaker OH masers at other wavelengths, such as 1667MHz or 22MHz.[3]
Examples
OH/IR stars
R Aquilae
HD 328913
UX Pictoris
AU Cygni
T Comae Berenices
SS Puppis
OH/IR supergiants
VY Canis Majoris
NML Cygni
S Persei
VX Sagittarii
WOH G64
HD 143183
IRAS 05280-6910
MY Cephei
References
Kemper, F.; De Koter, A.; Waters, L. B. F. M.; Bouwman, J.; Tielens, A. G. G. M. (2002). "Dust and the spectral energy distribution of the OH/IR star OH 127.8+0.0: Evidence for circumstellar metallic iron". Astronomy and Astrophysics. 384 (2): 585. arXiv:astro-ph/0201128. Bibcode:2002A&A...384..585K. doi:10.1051/0004-6361:20020036. S2CID 17649812.
Goldreich, P.; Scoville, N. (1976). "OH-IR stars. I - Physical properties of circumstellar envelopes" (PDF). Astrophysical Journal. 205: 144. Bibcode:1976ApJ...205..144G. doi:10.1086/154257.
Lewis, B. M. (2002). "On Dead OH/IR Stars". The Astrophysical Journal. 576 (1): 445–449. Bibcode:2002ApJ...576..445L. doi:10.1086/341534.
vte
Accretion Molecular cloud Bok globule Young stellar object
Protostar Pre-main-sequence Herbig Ae/Be T Tauri FU Orionis Herbig–Haro object Hayashi track Henyey track
Main sequence Red-giant branch Horizontal branch
Red clump Asymptotic giant branch
super-AGB Blue loop Protoplanetary nebula Planetary nebula PG1159 Dredge-up OH/IR Instability strip Luminous blue variable Blue straggler Stellar population Supernova Superluminous supernova / Hypernova
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O B A F G K M Brown dwarf WR OB Subdwarf
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S CN CH White dwarf Chemically peculiar
Am Ap/Bp HgMn Helium-weak Barium Extreme helium Lambda Boötis Lead Technetium Be
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Related articles
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