EDP Sciences
Free access
Volume 404, Number 1, June II 2003
Page(s) 305 - 315
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20030422

A&A 404, 305-315 (2003)
DOI: 10.1051/0004-6361:20030422

Photometry and low resolution spectroscopy of hot post-AGB candidates

G. Gauba1, M. Parthasarathy1, Brijesh Kumar2, R. K. S. Yadav2 and R. Sagar1, 2

1  Indian Institute of Astrophysics, Koramangala, Bangalore 560034, India
2  State Observatory, Manora Peak, Nainital 263129 (Uttaranchal), India

(Received 5 June 2002 / Accepted 7 March 2003 )

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 H $\alpha$ filter, to search for nebulosity around the central stars. Our H $\alpha$ 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 H $\alpha$ 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.

Key words: stars: AGB and post-AGB -- stars: early-type -- stars: evolution -- stars: mass-loss -- stars: circumstellar matter

Offprint request: G. Gauba, gauba@iiap.ernet.in

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© ESO 2003