The contribution by luminous blue variable stars to the dust content of
  the Magellanic Clouds
  (Shortened) Luminous blue variable stars (LBVs) form dust as a result of
episodic, violent mass loss. To investigate their contribution as dust
producers in the Magellanic Clouds, we analyse 31 LBVs from a recent census. We
built a maximally complete multi-wavelength dataset of these sources from
archival data from near-IR to millimetre wavelengths. We review the LBV
classification on the basis of the IR SED. To derive characteristic dust
parameters, we fitted the photometry resulting from a stacking analysis. For
comparison we also stacked the images of low- and intermediate-mass evolved
stars in the LMC. We find four classes of sources: 1) LBVs showing mid-IR dust
emission plus near-IR free-free emission from an ionised stellar wind (Class
1a) or only mid-IR dust emission (Class 1b); 2) LBVs with a near-IR excess due
to free-free emission only (Class 2); 3) objects with an sgB[e] classification;
and 4) objects with no detected stellar winds and no circumstellar matter in
their SEDs. From the stacking analysis of the 18 Class 1 and 2 objects in the
LMC, we derived an integrated dust mass of $0.11^{+0.06}_{-0.03} M_\odot$. This
is two orders of magnitude larger than the value inferred from stacking 1342
extreme-AGB stars. The dust mass of individual LBVs does not correlate with the
stellar parameters, possibly suggesting that the dust production mechanism is
independent of the initial stellar mass or that the stars have different
evolutionary histories. The total dust yield from LBVs over the age of the LMC
is $\sim 10^4-10^5 M_\odot$. LBVs are potentially the second most important
source of dust in normal galaxies. The role of dust destruction in LBV nebulae
by a possible subsequent SN blast wave has yet to be determined. Recent
theoretical developments in the field of dust processing by SN shocks highlight
the potential survival of dust from the pre-existing circumstellar nebula.
