  We have carried out an infrared search for obscured AGB stars in the
Magellanic Clouds. The survey uncovered a number of obscured AGB stars as well
as some supergiants with infrared excess. We present photometry of the sources
and discuss the colour diagrams and bolometric luminosities. Most of the AGB
stars are luminous, often close to the classical limit of $M_{\rm bol}=-7.1$.
  To determine whether the stars are oxygen-rich or carbon-rich, we have
acquired narrow-band mid-infrared photometry with the ESO TIMMI camera for
several sources. All but one are found to show the silicate feature and
therefore to have oxygen-rich dust: the colours of the remaining source are
consistent with either an oxygen-rich or a carbon-rich nature. A method to
distinguish carbon and oxygen stars based on H$-$K versus K$-$[12] colours is
presented.
  We discuss several methods of calculating the mass-loss rate: for the AGB
stars the mass-loss rates vary between approximately 5 times 10**-4 and 5 times
10**-6 solar masses per year, depending on assumed dust-to-gas mass ratio. We
present a new way to calculate mass-loss rates from the OH-maser emission. We
find no evidence for a correlation of the mass-loss rates with luminosity in
these obscured stars. Neither do the mass-loss rates for the LMC and SMC stars
differ in any clear systematic way from each other. Expansion velocities appear
to be slightly lower in the LMC than in the Galaxy.
  Period determinations are discussed for two sources: the periods are
comparable to those of the longer-period galactic OH/IR stars. All of the
luminous stars for which periods are available, have significantly higher
luminosities than predicted from the period--luminosity relations.

Astrophysics