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Optical and Ultraviolet Spectral Morphology of Luminous OB Stars in the Galaxy and the Magellanic Clouds

Published online by Cambridge University Press:  04 August 2017

Nolan R. Walborn
Nolan R. Walborn*
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, U.S.A.

Abstract

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Three areas of current progress relevant to the theme of this Symposium will be discussed. (1) New spectroscopic observations of the 30 Doradus central cluster, obtained independently by the author and by J. Melnick, confirm the presence of numerous very early O-type members, including several of type O3. In combination with sophisticated new direct imagery of the luminous central object R136 by A. Walker and by G. Weigelt, these results have evident implications for understanding the ionization of the supergiant H II region, as well as for the interpretation of R136 itself and of the apparently similar regions seen in more distant galaxies. In particular, no evidence remains for a supermassive object in 30 Doradus, but its central cluster is revealed as a spectacular grouping of very massive hot stars. (2) A further member of the Ofpe/WN9 category in the LMC has been identified, bringing their number to seven, with no exact spectroscopic counterparts yet known in the Galaxy. One of these objects is currently in a state of outburst and has been interpreted by O. Stahl et al. as the hottest known Hubble-Sandage variable. (3) An extensive survey of IUE high-resolution data has revealed a strong correlation between the ultraviolet stellar wind features and the optical spectral classifications for the majority of normal O stars. These results are relevant to future studies with the High Resolution Spectrograph on the Hubble Space Telescope, which may observe restricted UV wavelength ranges in faint extragalactic OB stars lacking optical data of comparable quality.

Type
Session 4. Other Luminous Stars with Emission Lines
Information
Symposium - International Astronomical Union , Volume 116: Luminous Stars and Associations in Galaxies , 1986 , pp. 185 - 198
Copyright
Copyright © Reidel 1986 

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