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Infrared imaging and spectroscopy of the Luminous Blue Variables Wra 751 and AG Car

Voors, RHM; Waters, LBFM; de Koter, A; Bouwman, J; Morris, PW; Barlow, MJ; Sylvester, RJ; ... Lamers, HJGLM; + view all (2000) Infrared imaging and spectroscopy of the Luminous Blue Variables Wra 751 and AG Car. Astronomy & Astrophysics , 356 (2) pp. 501-516. Green open access

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Abstract

We present ground-based infrared imaging and ISO spectroscopy of the luminous blue variables Wra 751 and AG Car. The images show in both cases a detached shell with a roughly circular distribution of emission. The infrared images of AG Car coincide very well with the optical images. The optical (H[FORMULA]) image of Wra 751 is different from the infrared image; the H[FORMULA] nebula is suggested to be a scattering nebula containing cold dust particles. Fitting both the images and the spectra consistently with a 1-D radiative transfer model, we derive properties of their dust shells. Wra 751 is surrounded by a dust shell with inner and outer radii of 0.17 and 0.34 pc respectively and a dust mass of 0.017 [FORMULA]. The dust shell of AG Car has inner and outer radii of 0.37 and 0.81 pc respectively and a total dust mass of 0.25 [FORMULA]. Dust mass-loss rates during the formation of the shells are 2.7[FORMULA] and 3.4[FORMULA] [FORMULA] yr-1, respectively. The total dust mass and hence the derived dust mass-loss rates are uncertain by at least a factor of two. For AG Car, the derived dust mass and mass-loss rate are higher than previous estimates. This is mainly caused by the fact that a contribution of very large grains ([FORMULA] 10 µm) is needed to explain the flux levels at longer wavelengths. Dust models for both objects fail to explain the flux shortward of 15 to 20 µm: a population of small warm grains, not in thermal equilibrium with the central star is necessary to explain this excess. Similarities between dust shells around Wolf-Rayet stars and Wra 751 and AG Car (mass, grain size population, morphology) suggest a similar formation history and imply an evolutionary connection. A similar connection with red supergiants is suggested on the basis of the dust composition and derived time-averaged mass-loss rates.

Type: Article
Title: Infrared imaging and spectroscopy of the Luminous Blue Variables Wra 751 and AG Car
Open access status: An open access version is available from UCL Discovery
Publisher version: http://aa.springer.de/bibs/0356002/2300501/small.h...
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: stars: circumstellar matter – stars: evolution – stars: individual: Wra 751, AG Car – stars: mass-loss
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10095239
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