We have determined the kinetic temperature of the electron gas as a function of position in the circumstellar envelopes of early Be stars for the model developed by Poeckert & Marlborough. The rates of energy gain and loss due to photoionization, radiative recombination, collisional transitions between bound levels, free-free emission, and free-free absorption were calculated at a set of grid points in a meridional plane. If the temperature assumed is correct, the ratio of energy gain to energy loss should be exactly 1 at all points in the envelope. Our investigation demonstrates that the choice of a constant temperature of 20,000 K was a reasonable first-order approximation. More importantly, we have also determined the temperature that corresponds to equal rates of energy gain and loss at each grid point throughout the envelope. These temperatures represent a self-consistent solution of the equation of energy conservation.

Rates of Energy Gain and Loss in the Circumstellar Envelopes of Be Stars

Assuming Case B of Baker and Menzel (1938), the relative intensities of H I and He II recombination lines are determined for a larger range of temperature and density than previously considered and with the upper principle quantum number up to 50 and the lower number up to 29. Full collisional effects are included, and new collision strengths for the n = 1, 2, and 3 states of He(+) are presented. Case B theory is found to be invalidated for collisional excitation of the n = 3 levels from both n = 1 and n = 2 states under certain conditions which depend upon electron density and the Lyman-alpha escape probability, and the regimes of temperature and density for which Case B is valid are also considered.

Recombination-line intensities for hydrogenic ions. I - Case B calculations for H I and He II. [in astronomical objects

. We discuss the infrared spectral energy distribution of Be stars, focusing on new results obtained with the Infrared Space Observa tory. The 60-160 fira flux of some Be stars is higher than expected, which may be due to cold dust or an outer disk component with enhanced den sities. The infrared spectrum of Be stars is dominated by numerous HI recombination lines, whose line strengths show a complex behaviour. The electron temperature in the disk of 7 Cas was found to be about 9500 K, and evidence for an elevated temperature near the upper part of the disk is presented. Be stars may be recognized from their infrared spectrum on the basis of HI line flux ratios.

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ISO observations of Be stars

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ISO observations of Be stars