date:Observ Astron Nacl, IGN, Alcala De Henares 28800, Spain; CNRS, Inst Astrophys Paris, F-75014 Paris, France; ESA, Dept Space Sci, Div Astrophys, ISO Data Ctr, Madrid 28080, Spain; Max Planck Inst Astrophys, D-85740 Garching, Germany; Univ Paris 07, F-75251 Paris 05, France
We present the analysis of infrared photometry and millimeter spectroscopy of a sample of 74 late-type supergiants. These observations are particularly suitable to study the mass loss and the circumstellar envelopes of evolved massive stars. In particular, we quantify the circumstellar infrared excess, the relation of mass loss with stellar properties, using the K- colour index as mass-loss indicator. We do not find any clear correlation between mass loss rate and luminosity. We also show that the K-band magnitude is a simple luminosity indicator, because of the relative constancy of the K-band bolometric correction.