IUE and ground-based observations of the Hubble-Sandage variables in M 31 and M 33.

Abstract

Ultraviolet spectroscopy from the IUE, in combination with ground-based visual and infrared photometry, are used to determine the energy distributions of the luminous blue variables, the Hubble-Sandage variables, in M31 and M33. When corrected for interstellar extinction, the integrated energy distributions yield the total luminosities and blackbody temperatures of the stars. These stars occupy the same regions of the M_bol versus temperature diagram as do η Car and P Cyg in our Galaxy and S Dor in the LMC. Many of the Hubble-Sandage variables have excess infrared radiation which is attributed to free-free emission from their extended atmospheres. Rough mass loss estimates from the infrared excess yield rates of 10^-5M_sun;yr^-1.