We have modeled the 2.6 – 3.7 \mbox { $ \mu$m } spectrum of the red semiregular variable R Doradus observed with the Short-Wavelength Spectrometer on board the Infrared Space Observatory .
The wavelength resolution of the observations varies between \mathrm { R } \sim 2000 – 2500 .
We have calculated a synthetic spectrum using a hydrostatic model photosphere in spherical geometry .
The agreement between the synthetic spectrum and the ISO observations is encouraging , especially in the wavelength region of 2.8 – 3.7 \mbox { $ \mu$m } , suggesting that a hydrostatic model photosphere is adequate for the calculation of synthetic spectra in the near infrared for this moderately varying red giant star .
However , an additional absorption component is needed at 2.6 – 2.8 \mbox { $ \mu$m } and this discrepancy is discussed .
The spectral signatures are dominated by water vapour in the stellar photosphere , but several photospheric OH , CO , and SiO features are also present .
The effective temperature and surface gravity derived for R Dor , based on the 2.6 – 3.7 \mbox { $ \mu$m } ISO spectrum and the modeling of it with a hydrostatic model photosphere , are 3000 \pm 100 \mbox { K } and \log g = 0 \pm 1 ( cgs ) , respectively .
The spectral region observed is found to be temperature sensitive .
The effective temperature given here is slightly higher than those reported in the literature .
We also discuss possible reasons for this .