Axi-symmetric Models of B[e] Supergiants - I. The Effective Temperature and Mass-loss Dependence of the Hydrogen and Helium Ionization Structure

Aug 26, 2026

Calculations of hydrogen and helium ionization in B[e] envelopes assess how ionization depends on mass-loss rate and effective temperature. Simulated observables include the Hδ emission line and the C IV λλ1550 doublet, with emphasis on how these diagnostics respond to model parameters. The work presents first results of a broader study of sgB[e] supergiants, illustrating ionization behavior for key elements in self-consistent numerical simulations.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages11

Reading Time28 min

AccessFree to download

Abstract

Aims

Methods

Results

Ionization structure and disk formation

Spectral-line features

Key words

1. Introduction

arXiv : 07 12 .0870v1 [ astro-ph] 6 Dec 2007 Astronomy & Astrophysics manuscript no. 8293ms 􀀍c ESO 2018 October 27, 2018 Axi-symmetric Models of B[e] Supergiants: I. The E􀀋ective Temperature and Mass-loss Dependence of the Hydrogen and Helium Ionization Structure J. Zsarg􀀓o1 , D. J. Hillier 1 , and L. N. Georgiev2 1 Dept. of Physics and Astronomy, University of Pittsburgh, 3941 O’Hara St. , Pittsburgh, PA 15260, USA 2 Instituto de Astronomia, Universidad Nacional Autonoma de Mexico (UNAM), CD. Universitaria, Apartado Postal 70-264, 04510, M􀀓exico DF, M􀀓exico Received DD MM 200Y/ Accepted DD MM 200Y ABSTRACT Aims. We calculate the hydrogen and helium ionization in B[e] envelopes and explore their dependence on mass-loss ande􀀋ective temperature. We also present simulated observations of the H􀀋 emission line and the C IV 􀀕􀀕1550 doublet, and study their behavior. This paper reports our 􀀌rst results in an ongoing study of B[e] supergiants, and provides a glimpse on the ionization of the most important elements in self-consistent numerical simulations. Methods. Our newly developed 2D stellar atmosphere code, ASTAROTH, was used for the numerical simulations. The code self-consistently solves for the continuum radiation, non-LTE level populations, and electron temperature inaxi-symmetric stellar envelopes. Observed pro􀀌les were calculated by an auxiliary program developed separately from ASTAROTH. Results. In all but one of our models, H remained fully ionized—only for M˙> 10−5 M⊙ yr−1 and Teff ≤18,000 K did we obtain a neutral H disk, and then only for radii beyond 3R∗ . Due to ionizations from excited states it is much more di􀀎cult to get a H neutral disk than indicated by previous analytical calculations. Near the poles, the ionization is high in all models, while helium recombined in the equatorial regions for all but our lowest mass-loss rate (10−6 M⊙ yr−1) . Although the model parameters were not adjusted to provide 􀀌ts to any particular star, the theoretical pro􀀌les show some features seen in the pro􀀌les of R126 . These include the partially resolved double peaked pro􀀌le of H􀀋, and the weak emission associated with the UV C iv resonance line. Key words. Physical data and processes: Radiative transfer – Stars: early-type – Stars: atmospheres – Stars: mass-loss 1. Introduction Massive stars are very important constituents of the Universe despite their low share of galactic masses. They are the primary sources of elements heavier than Li and power the internal evolution of galaxies by their radiation, winds, and explosions. Many of these stars, and their immediate environment, cannot be fully understood in the context of plane-parallel or spherical models, and their multidimensional nature has to be taken into account if their evolution or physical state is to be adequately described. The origin of their asphericity is either fast rotation, the presence of a dynamically important magnetic 􀀌eld, or their interaction with a companion. Three groups of such stars are particularly relevant for this paper. These are the classical Be stars, the Luminous Blue Variables (LBV), and the B[e] supergiants (sgB[e]), all of which share many similar characteristics. The 2Dor 3D nature of these objects was recognized through both observations and theoretical calculations. For example, the presence of disks around classical Be stars was inferred from line modeling and polarimetric studies (Poeckert & Marlborough 1978a,b), and has been con- 􀀌rmed by interferometric observations (Stee et al. 1995; Quirrenbach et al. 1997) . Similarly, a growing body of evidence suggests that the LBV phenomenon includes 2D or 3D processes. For example, 􀀑 Car is a binary (Damineli et al. 2000) and the Homunculus nebula around it is the most cited example of a bipolar out􀀍ow. The aspherical envelope of 􀀑 Car is not unique among LBVs; Groh et al. (2006) found that AG Car is a fast rotator, and hence may have a latitude dependent wind. Th

FAQs

What is the main aim of this study on B[e] supergiants?

The study calculates hydrogen and helium ionization in B[e] envelopes and examines how ionization depends on mass loss and effective temperature.

Which tools are used for the numerical simulations and predicted profiles?

The ASTAROTH 2D stellar atmosphere code performs self-consistent simulations, while an auxiliary program calculates observed spectral profiles.

Under what conditions does the model produce a neutral hydrogen disk?

Neutral hydrogen appears only in one set of cases, requiring high mass-loss (above 10−5 M⊙ yr−1) and lower effective temperatures (Teff ≤ 18,000 K), and only beyond 3R∗.

Aug 26, 2026

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