OH/IR star
Type of star
From Wikipedia, the free encyclopedia
An OH/IR star is an asymptotic giant branch (AGB), a red supergiant (RSG), or a red hypergiant (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
OH/IR supergiants
- S Persei
- VX Sagittarii
- V1804 Sagittarii[6][a]
- VY Canis Majoris
- AH Scorpii
- MY Cephei
- PZ Cassiopeiae
- IRC −30308
- NML Cygni
- IRC +10420
- WOH G64 A[7]
- IRAS 05280−6910[8]
- IRC −10414[9]
- RSGC1-F13[10]
- CD-34 11794[11][12][13]
Notes
- Although various papers considered it a luminous and peculiar very late-type red supergiant with a 1974 paper deriving a spectral type of M9.1 Iap, few papers and SIMBAD considered it a Mira variable and an AGB star.
