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Title:
Infrared excess and mass-loss rate of the extreme Of star HD 108
Authors:
Ferrari-Toniolo, M.; Persi, P.; Grasdalen, G. L.
Affiliation:
AA(CNR, Istituto di Astrofisica Spaziale, Frascati, Italy), AB(CNR, Istituto di Astrofisica Spaziale, Frascati, Italy), AC(Wyoming, University, Laramie, WY)
Publication:
Astronomical Society of the Pacific, Publications, vol. 93, Oct.-Nov. 1981, p. 633-635. (PASP Homepage)
Publication Date:
10/1981
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
INFRARED ASTRONOMY, MASS FLOW RATE, O STARS, STELLAR MASS EJECTION, STELLAR SPECTROPHOTOMETRY, STELLAR WINDS, INFRARED PHOTOMETRY, RADIANT FLUX DENSITY, RADIATION PRESSURE, SPECTRAL ENERGY DISTRIBUTION, STELLAR ATMOSPHERES, STELLAR ENVELOPES, ULTRAVIOLET SPECTRA
Comment:
A&AA ID. AAA030.112.041
DOI:
10.1086/130900
Bibliographic Code:
1981PASP...93..633F

Abstract

Infrared observations are presented for the extreme Of star HD 108 and used to derive an estimate of the mass loss rate of the object to compare with the widely differing values derived from optical and UV observations. Broadband infrared photometry was obtained at wavelengths from 2.3 to 10 microns with a multifilter Ge bolometer at a 2.3-m telescope. The infrared excess spectrum derived from the difference between observed fluxes and the stellar continuum represented by the Kurucz (1979) model atmosphere with an effective temperature of 35,000 K and log g 3.5 can be fit by an isothermal free-free + bound-free emission spectrum from an optically thick circumstellar envelope with an electron temperature of 30,000 K and an inverse square electron density-radius relation. The measured infrared excess at 10 microns is used, together with a nonconstant wind velocity law, to obtain a mass loss rate for HD 108 of about 0.00005 solar masses/year, one of the highest values obtained for O-type stars and comparable to that derived for WR stars. This value indicates that radiation pressure alone is insufficient to drive the observed mass loss rate and wind velocity.

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