Context : Extremely reddened asymptotic giant branch stars ( AGB ) lose mass at high rates of > 10 ^ { -5 } M _ { \odot } yr ^ { -1 } .
This is the very last stage of AGB evolution , in which stars in the mass range \sim 2.0 – 4.0 M _ { \odot } ( for solar metallicity ) should have been converted to C stars already .
The extremely reddened AGB stars in the Galactic bulge are however predominantly O-rich , implying that they might be either low-mass stars or stars at the upper end of the AGB mass range .

Aims : Our goal is to determine the mass range of the most reddened AGB stars in the Galactic bulge .

Methods : Using Virtual Observatory tools , we constructed spectral energy distributions of a sample of 37 evolved stars in the Galactic bulge with extremely red IRAS colours .
We fitted DUSTY models to the observational data to infer the bolometric fluxes .
Applying individual corrections for interstellar extinction and adopting a common distance , we determined luminosities and mass-loss rates , and inferred the progenitor mass range from comparisons with AGB evolutionary models .

Results : The observed spectral energy distributions are consistent with a classification as reddened AGB stars , except for two stars , which are proto-planetary nebula candidates .
For the AGB stars , we found luminosities in the range \sim 3000 – 30,000 L _ { \odot } and mass-loss rates \sim 10 ^ { -5 } – 3 \times 10 ^ { -4 } M _ { \odot } yr ^ { -1 } .
The corresponding mass range is \sim 1.1 – 6.0 M _ { \odot } assuming solar metallicity .

Conclusions : Contrary to the predictions of the evolutionary models , the luminosity distribution is continuous , with many O-rich AGB stars in the mass range in which they should have been converted into C stars already .
We suspect that bulge AGB stars have higher than solar metallicity and therefore may avoid the conversion to C-rich .
The presence of low-mass stars in the sample shows that their termination of the AGB evolution also occurs during a final phase of very high mass-loss rate , leading to optically thick circumstellar shells .