On the hydrogen neutral outflowing disks of B[e] supergiants

Abstract

(abridged) B[e] supergiants are known to possess geometrically thick dusty disks. Disk-forming wind models have, however, been found to be insufficient in reproducing the observed dust emission. This problem arises due to the severe assumption that, as for classical Be stars, the near-infrared excess emission originates in the disk. Modeling of the free-free and free-bound emission therefore results in an upper limit for the disk mass loss rate, hampering dust condensation in the disk. We propose a revised scenario for the non-spherical winds of B[e] supergiants: a normal B-type line-driven polar wind and an outflowing disk-forming wind that is neutral in hydrogen at, or very close to the stellar surface. We concentrate on the pole-on seen LMC B[e] supergiant R126 and calculate the line luminosities of the optical [OI] emission lines with an outflowing disk scenario. In addition, we compute the free-free and free-bound emission from a line-driven polar wind and model the spectral energy distribution in the optical and near-infrared. Good fits to the [OI] line luminosities are achieved for an outflowing disk that is neutral in hydrogen right from the stellar surface. Neutral thereby means that hydrogen is ionized by less than 0.1%. Consequently, the free-free and free-bound emission cannot (dominantly) arise from the disk and cannot limit the disk mass loss rate. The hydrogen neutral outflowing disk scenario therefore provides an ideal environment for efficient dust formation. The spectral energy distribution in the optical and near-infrared range can be well fitted with the stellar continuum plus free-free and free-bound emission from the polar line-driven wind. Our modeling further delivers minimum values for \dot{M}(disk) > 2.5d-5 M_sun/yr and for the density contrast between equatorial and polar wind of ~10.

arXiv comment9 pages, 8 figures, accepted for publication in A&A

References in corpus (3)

• On the optical--infra-red continuum emission from equatorial discs of supergiant B[e] stars
• Ionization structure in the winds of B[e] supergiants: I. Ionization equilibrium calculations in a H plus He wind
• Ionization structure in the winds of B[e] supergiants II. Influence of rotation on the formation of equatorial hydrogen neutral zones

Cited by in corpus (17)

• A Spitzer Space Telescope far-infrared spectral atlas of compact sources in the Magellanic Clouds. I. The Large Magellanic Cloud
• The supergiant B[e] star LHA 115-S 18 - binary and/or luminous blue variable?
• A new observational tracer for high-density disc-like structures around B[e] supergiants
• Spectroscopic survey of emission-line stars. I. B[e] stars
• Resolving the kinematics of the disks around Galactic B[e] supergiants
• The circumstellar environment and evolutionary state of the supergiant B[e] star Wd1-9
• Broadband ESO/VISIR-Spitzer infrared spectroscopy of the obscured supergiant X-ray Binary IGR J16318-4848
• Discovery of the first B[e] supergiants in M 31
• Supernova explosions interacting with aspherical circumstellar material: implications for light curves, spectral line profiles, and polarization
• The dustiest Post-Main sequence stars in the Magellanic Clouds
• From B[e] to A[e]. On the peculiar variations of the SMC supergiant LHA 115-S 23 (AzV 172)
• Discovery of Raman-scattered lines in the massive luminous emission-line star LHA 115-S 18
• The sudden appearance of CO emission in LHA 115-S 65
• VLTI/AMBER observations of the binary B[e] supergiant HD 327083
• Two-dimensional modeling of density and thermal structure of dense circumstellar outflowing disks
• The galactic unclassified B[e] star HD 50138 III. The short-term line profile variability of its photospheric lines
• Disk tracing for B[e] supergiants in the Magellanic Clouds