OH/IR star (original) (raw)
OH/IR-Sterne sind hinter einer Staubhülle verborgene Rote Riesen, die Strahlung überwiegend im Infraroten und sub-mm-Bereich aussenden. Das OH im Namen stammt vom Hydroxylradikal, dessen typische Emissionslinie im Spektrum dieser Sterne enthalten ist.
| Property | Value |
|---|---|
| dbo:abstract | OH/IR-Sterne sind hinter einer Staubhülle verborgene Rote Riesen, die Strahlung überwiegend im Infraroten und sub-mm-Bereich aussenden. Das OH im Namen stammt vom Hydroxylradikal, dessen typische Emissionslinie im Spektrum dieser Sterne enthalten ist. (de) 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. Hydroxyl (OH) radicals can be produced by photodissociation or collisional dissociation. 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. (en) Une étoile à émission OH/IR est une étoile de la branche asymptotique des géantes (AGB = asymptotic giant branch) qui présente une forte émission maser OH et est inhabituellement brillante aux longueurs d'onde du proche-infrarouge. Dans les stades très tardifs de l'évolution AGB, une étoile développe une super-vent avec une perte de masse extrême. Le gaz du vent stellaire se condense en s'éloignant de l'étoile, formant des molécules telles que l'eau (H2O) et le monoxyde de silicium (SiO). Ils peuvent former des , principalement des silicates, qui obscurcissent l'étoile aux longueurs d'onde plus courtes, donnant une forte source infrarouge. Les radicaux hydroxyles (OH) peuvent être produits par photodissociation ou par dissociation collisionnelle. H2O et OH peuvent être tous deux pompés pour produire une émission maser. Les masers OH en particulier peuvent donner lieu à une puissante émission maser à 1 612 MHz et ceci est considéré comme une caractéristique définissant les étoiles OH/IR. Beaucoup d'autres étoiles AGB telles que les variables de type Mira possèdent des masers OH plus faibles à d'autres longueurs d'onde, telles que 1 667 MHz ou 22 MHz. (fr) Een OH/IR ster is een geëvolueerde laat type ster die OH-maseremissie vertoont en die helder is in het nabij en midden infrarood. In het Hertzsprung-Russelldiagram liggen OH/IR sterren op de asymptotische reuzentak. (nl) Uma estrela OH/IR é uma estrela do ramo gigante assimptótico (asymptotic giant branch – AGB) que mostra forte emissão de maser OH e é, de forma pouco usual, brilhante em comprimentos de onda próximos ao infravermelho. Nos últimos estágios da evolução AGB, a estrela desenvolve um supervento, com perda extrema de massa. O gás no vento estelar condensa quando se resfria longe da estrela, formando moléculas como água (H2O) e monóxido de silício (SiO). Isto pode formar grãos de poeira, na maior parte silicatos, que obscurecem a estrela em comprimentos de onda menores, levando a uma forte fonte de infravermelho. Radicais hidroxila (OH) podem ser produzidos por fotodissociação ou por dissociação colisional. H2O e OH podem ser bombeados para produzir a emissão de maser. Masers OH em particular podem gerar uma poderosa ação de maser a 1612 MHz e isto é visto como uma característica definidora para as estrelas OH/IR. Muitas outras estrelas AGB, como as variáveis Mira, mostram masers OH mais fracos em outros comprimentos de onda, como 1667 MHz ou 22 MHz. (pt) OH/IR星是演化晚期型星，顯示出在近紅外線波段明亮的OH邁射輻射。 在米拉變星，恆星外層的大氣層在脈動的峰執會被強勁的星風吹離。而在吹離恆星時，星周包層的氣體會迅速地凝結，形成像水和氧化矽等分子。氧化矽的分子結合創造出塵埃顆粒，水分子可以被其他恆星輻射的紫外線分解成羥基的分子。來自溫暖塵埃的熱會激發羥基，而被激發的羥基分子會發出邁射的1612MHz和1667MHz的譜線。 短週期脈動（約一年）和低質量損失率的米拉變星在1667MHz的波長上產生微弱的邁射，但是高質量損失率和長週期脈動（最長約六年）的米拉變星在1612MHz的羥基邁射會變得比1667MHz的強烈。它們使從恆星膨脹的氣體殼層發射出的譜線特徵形成U字型的形狀。這種恆星因為從殼層溫暖的氣體輻射出強烈的羥基（OH）邁射和紅外線，因而被稱為OH/IR 星。 邁射的強度會隨著恆星亮度的脈動變化。 兩個峰值的速度差值等於殼體中的氣體和塵埃離開恆星膨脹速度的兩倍，典型的膨脹速度是大約每秒20公里。左邊的峰值在右邊的之前升起，也在右邊的落下之前先落下。這是無線電波的邁射從遠端穿越殼層到近端需要額外的時間造成的結果。 (zh) |
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| rdfs:comment | OH/IR-Sterne sind hinter einer Staubhülle verborgene Rote Riesen, die Strahlung überwiegend im Infraroten und sub-mm-Bereich aussenden. Das OH im Namen stammt vom Hydroxylradikal, dessen typische Emissionslinie im Spektrum dieser Sterne enthalten ist. (de) Een OH/IR ster is een geëvolueerde laat type ster die OH-maseremissie vertoont en die helder is in het nabij en midden infrarood. In het Hertzsprung-Russelldiagram liggen OH/IR sterren op de asymptotische reuzentak. (nl) OH/IR星是演化晚期型星，顯示出在近紅外線波段明亮的OH邁射輻射。 在米拉變星，恆星外層的大氣層在脈動的峰執會被強勁的星風吹離。而在吹離恆星時，星周包層的氣體會迅速地凝結，形成像水和氧化矽等分子。氧化矽的分子結合創造出塵埃顆粒，水分子可以被其他恆星輻射的紫外線分解成羥基的分子。來自溫暖塵埃的熱會激發羥基，而被激發的羥基分子會發出邁射的1612MHz和1667MHz的譜線。 短週期脈動（約一年）和低質量損失率的米拉變星在1667MHz的波長上產生微弱的邁射，但是高質量損失率和長週期脈動（最長約六年）的米拉變星在1612MHz的羥基邁射會變得比1667MHz的強烈。它們使從恆星膨脹的氣體殼層發射出的譜線特徵形成U字型的形狀。這種恆星因為從殼層溫暖的氣體輻射出強烈的羥基（OH）邁射和紅外線，因而被稱為OH/IR 星。 邁射的強度會隨著恆星亮度的脈動變化。 兩個峰值的速度差值等於殼體中的氣體和塵埃離開恆星膨脹速度的兩倍，典型的膨脹速度是大約每秒20公里。左邊的峰值在右邊的之前升起，也在右邊的落下之前先落下。這是無線電波的邁射從遠端穿越殼層到近端需要額外的時間造成的結果。 (zh) 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. Hydroxyl (OH) radicals can be produced by photodissociation or collisional dissociation. (en) Une étoile à émission OH/IR est une étoile de la branche asymptotique des géantes (AGB = asymptotic giant branch) qui présente une forte émission maser OH et est inhabituellement brillante aux longueurs d'onde du proche-infrarouge. (fr) Uma estrela OH/IR é uma estrela do ramo gigante assimptótico (asymptotic giant branch – AGB) que mostra forte emissão de maser OH e é, de forma pouco usual, brilhante em comprimentos de onda próximos ao infravermelho. H2O e OH podem ser bombeados para produzir a emissão de maser. Masers OH em particular podem gerar uma poderosa ação de maser a 1612 MHz e isto é visto como uma característica definidora para as estrelas OH/IR. Muitas outras estrelas AGB, como as variáveis Mira, mostram masers OH mais fracos em outros comprimentos de onda, como 1667 MHz ou 22 MHz. (pt) |
| rdfs:label | OH/IR-Stern (de) Étoile à émission OH/IR (fr) OH/IR star (en) OH/IR-ster (nl) Estrela OH/IR (pt) OH/IR星 (zh) |
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