Photometry and low resolution spectroscopy of hot post-AGB candidates

We have obtained Johnson U, B, V and Cousins R, I photometry and low resolution spectra of a small sample of hot post-AGB candidates. Using the present data in combination with JHK data from 2MASS, infrared data from the MSX catalog and the IRAS fluxes, we have studied the spectral energy distribution ( SED) of these stars. Using the DUSTY code we have estimated the dust temperatures, the distances to the stars, the mass-loss rates, angular radii of the inner boundary of the dust envelopes and dynamical ages from the tip of the AGB. These candidates have also been imaged through a narrow band Ha filter, to search for nebulosity around the central stars. Our Ha images revealed the bipolar morphology of the low excitation PN IRAS 17395-0841 with an angular extent of 2.8. The bipolar lobes of IRAS 17423-1755 in Ha were found to have an angular extent of 3.5 (south-east lobe) and 2.2 (north-west lobe). The dust envelope characteristics, low resolution spectrum and IRAS colors suggest that IRAS 18313-1738 is similar to the proto-planetary nebula (PPN) HD 51585. The SED of IRAS 17423-1755, IRAS 18313-1738 and IRAS 19127+1717 show a warm dust component ( in addition to the cold dust) which may be due to recent and ongoing mass-loss.