date:European So Observ, Space Telescope European Coordinating Facil, D-85748 Garching, Germany; Innsbruck Univ, Astron Inst, A-6020 Innsbruck, Austria; ESA, ISO Data Ctr, Madrid 28080, Spain; Max Planck Inst Astrophys, D-8046 Garching, Germany; Astron Observ, S-75120 Uppsala, Sweden
We present ISOCAM observations of Sakurai's object (V4334 Sgr) covering the wavelength range of 4 to 15 mu m in seven filters. The photometry shows that in the period from February 1997 to February 1998 the flux over the whole wavelength range has increased by a factor of about ten. Combined with ground-based data we conclude that this increase is the result of mass loss from Sakurai's object and the formation of hot dust around it. Using a spherically symmetric dust radiative transfer model we obtain a quantitative result of a variable and increasing mass loss rate reaching some 10(-7) M./yr, a value not uncommon among stars during the Asymptotic Giant Branch (AGB) evolution. This is in agreement with the notion that Sakurai's object is retracing its own evolutionary history as a consequence of a very late Helium flash. We conclusively demonstrate that significant mass loss is associated with such an event and foster the link to the other few known examples of final Helium flashes.