Water Vapor Absorption in Early M-type Stars

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dc.creatorMatsuura, M.
dc.creatorYamamura, I.
dc.creatorMurakami, H.
dc.creatorFreund, M. M.
dc.creatorTanaka, M.
dc.date1999-06-16
dc.date.accessioned2026-07-07T02:32:03Z
dc.date.available2026-07-07T02:32:03Z
dc.descriptionThe spectrometers onboard the Infrared Telescope in Space (IRTS) reveal water vapor absorption in early M-type stars, as early as M2. Previous observations detected H_2O vapor absorption only in stars later than M6, with the exception of the recent detection of H_2O in beta Peg (M2.5 II-III). In our sample of 108 stars, 67 stars have spectral types earlier than M6. The spectral types are established by means of their near-infrared colors on a statistical basis. Among the 67 stars of spectral types earlier than M6, we find water vapor absorption in six stars. The observed absorption features are interpreted using a local thermodynamic equilibrium model. The features are reasonably fitted by model spectra with excitation temperatures of 1000-1500 K and water column densities of 5x10^19 to 1x10^20 cm^-2. These numbers imply that the H_2O molecules are present in a region of the atmosphere, located above the photosphere. Furthermore, our analysis shows a good correlation between the H_2O absorption band strength, and the mid-infrared excess due to the circumstellar dust. We discuss the relation between the outer atmosphere and the mass loss.
dc.description5 pages with 6 figures, Accepted for A&A
dc.identifierhttps://arxiv.org/abs/astro-ph/9906264
dc.identifierhttp://arxiv.org/abs/astro-ph/9906264
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/14371
dc.subjectAstrophysics
dc.titleWater Vapor Absorption in Early M-type Stars
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