HST AND GROUNDBASED OBSERVATIONS OF THE HUBBLE-SANDAGE VARIABLES IN M31 AND M33

The small group of peculiar stars known as the Hubble-Sandage variable s in M 31 and M 33 belong to the class of stars we now call the Lumino us Blue Variables - highly unstable, evolved massive stars found in ma ny spiral and irregular galaxies. We have used the Hubble Space Telesc ope to obtain UV imaging and spectroscopy of several of the LBVs in M 31 acid M 33. The UV observations are combined with groundbased spectr a and optical and infrared photometry to estimate their apparent tempe ratures, luminosities, and mass loss rates. We were fortunate to catch Var B in M 33 during an LBV eruption while Var C in M 33 was observed during its decline from its recent maximum. Var B is especially inter esting because one of the optical spectra showed emission lines of He I, indicating a temperature of 20 000 K or more while the rest of the lines were typical of an LBV in eruption, at a temperature near 9000 K . With no other indication of a temperature or radial change, we sugge st the He I lines were excited by a shock or produced by hot radiation escaping from the polar regions. The UV spectrum of AE And shows an u nusually strong emission line of Fe II at 2507 Angstrom similar to eta Carinae. The spectra of AE And, AF And, and Var 83 in M 33, all obser ved at visual minimum, show a veritable forest of Fe II and [Fe II] em ission lines. This is in contrast to the quiescent spectra of some LBV s which resemble Of/WN9 stars, such as R 127 and AG Car.