2001AJ....121.2752H

The observed spectral energy distributions of a sample of 60 OH/IR stars are fitted using a radiative transfer model of a dusty envelope. Among the whole sample, 21 stars have reliable phase-lag distances, while the others have less accurate distances. L_*-P, M{dot}-P, and M{dot}-L_* relations have been plotted for these stars. It is found that type E (with an emission feature at 10 µm) and type A (with an absorption feature at 10 µm) OH/IR stars have different L_*-P and M{dot}-L_* relations, while both follow a single M{dot}-P relation. The type E stars are shown to be located in an area without large-scale dense interstellar medium, while the type A stars are probably located in dense interstellar medium. It is argued here that this may indicate that the two types of OH/IR stars do not share the same chemical composition or zero-age main-sequence mass and so evolve in different ways. This conclusion has reinforced the argument by Chen et al., who reached a similar conclusion from the Galactic distribution of about 1000 OH/IR stars, based on IRAS low-resolution spectrometer spectra.