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Infrared observations of circumstellar ejecta around Luminous Blue Variables

Published online by Cambridge University Press:  12 April 2016

Peter J. McGregor
Peter J. McGregor*
Affiliation:
Mount Stromlo and Siding Spring ObservatoriesInstitute of Advanced StudiesThe Australian National UniversityGPO Box 4, A.C.T. 2601, Australia

Abstract

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Recent infrared spectroscopy and imaging of LBVs lead to the following results. CO overtone emission at 2.3 μm has been found in 13 LBVs in the Galaxy and the LMC. This emission is collisionally excited in warm (3000 – 5000 K), dense (NH > 1010 cm-3) circumstellar material. Circumstellar disks offer favorable conditions for the formation and excitation of CO molecules and are very likely the location of the observed emission. It is proposed that the LBVs showing 2.3 μm CO overtone emission possess the highest density circumstellar disks.

A group of eight LBVs has been identified in the LMC with He I 2.058 μm emission stronger than H I Brγ. This group includes the CO emission star HD 37836. Helium is over-abundant in these stars with N(He)/N(H) ranging from 0.2 to >0.5. Remarkably five of the helium strong stars belong to the small class of Ofpe/WN9 stars and a further two are probably related to this class.

Slit scans of the galactic LBV AG Car have resolved the far-infrared emission from this star, clearly showing it to originate from cool dust in the circumstellar ring structure. Thermal equilibrium considerations require large grains in the ring in order to match the measured grain temperature and radial distance. Similar slit scans of the galactic B[e] star HD 87643 fail to resolve the far-infrared emission from this star at the 10″ level.

Type
Section I: Main Papers, General Discussions, and Two Panel Discussions
Information
International Astronomical Union Colloquium , Volume 113: Physics of Luminous Blue Variables , 1989 , pp. 165 - 176
Copyright
Copyright © Kluwer 1989

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