A spectroscopic atlas of post-AGB stars and planetary nebulae selected from the IRAS point source catalogue

Aims. We study the optical spectral properties of a sample of stars showing far infrared colours similar to those of well-known planetary nebulae. The large majority of them were unidentified sources or poorly known in the literature at the time when this spectroscopic survey started, some 15 years ago. Methods. We present low-resolution optical spectroscopy, finding charts and improved astrometric coordinates of a sample of 253 IRAS sources. Results. We have identified 103 sources as post-AGB stars, 21 as "transition sources", and 36 as planetary nebulae, some of them strongly reddened. Among the rest of sources in the sample, we were also able to identify 38 young stellar objects, 5 peculiar stars, and 2 Seyfert galaxies. Up to 49 sources in our spectroscopic sample do not show any optical counterpart, and most of them are suggested to be heavily obscured post-AGB stars, rapidly evolving on their way to becoming planetary nebulae. Conclusions. An analysis of the galactic distribution of the sources identified as evolved stars in the sample is presented together with a study of the distribution of these stars in the IRAS two-colour diagram. Finally, the spectral type distribution and other properties of the sources identified as post-AGB in this spectroscopic survey are discussed in the framework of stellar evolution.

[1]  Mark E. Cornell,et al.  A New Library of Stellar Optical Spectra , 1992 .

[2]  R. Cesaroni,et al.  A Survey for Water Maser Emission toward Planetary Nebulae: New Detection in IRAS 17347–3139 , 2003, astro-ph/0310415.

[3]  A. Agnès,et al.  Strasbourg-ESO Catalogue of Galactic Planetary Nebulae , 1993 .

[4]  D. Allen,et al.  Roberts 22 : a bipolar nebula with OH emission. , 1980 .

[5]  D. Morgan,et al.  Planetary Nebulae in the Magellanic Clouds , 1991 .

[6]  A. Acker,et al.  Quantitative classification of WR nuclei of planetary nebulae , 2003 .

[7]  A. Manchado,et al.  Near infrared photometry of IRAS sources with colours like planetary nebulae. III. , 1997 .

[8]  A. Manchado,et al.  Optical and Infrared Observations of the Bipolar Proto-Planetary Nebula Henize 401 , 1999 .

[9]  N. Scoville,et al.  Infrared sources in molecular clouds. , 1976 .

[10]  Planetary nebulae near the Galactic center: Identifications , 2004, astro-ph/0402280.

[11]  A. Acker,et al.  Strasbourg-ESO Catalogue of Galactic Planetary Nebulae , 1993 .

[12]  The spectral evolution of post-asymptotic giant branch stars , 1997 .

[13]  A. Pickles.  A Stellar Spectral Flux Library: 1150–25000 Å , 1998 .

[14]  P. Wood,et al.  Post-asymptotic giant branch evolution of low- to intermediate-mass stars , 1994 .

[15]  M. Barlow,et al.  Quantitative classification of WC and WO stars , 1998 .

[16]  M. Dopita,et al.  The evolutionary sequence of planetary nebulae , 1990 .

[17]  H. J. Habing,et al.  Circumstellar envelopes and Asymptotic Giant Branch stars , 1996 .

[18]  S. Kwok.  Proto-Planetary Nebulae , 1993 .

[19]  Hans Van Winckel,et al.  Post-AGB Stars , 2003 .

[20]  D. A. Hunter,et al.  A library of stellar spectra. , 1984 .

[21]  A. Manchado,et al.  Infrared Space Observatory Observations of IRAS 16594–4656: A New Proto-Planetary Nebula with a Strong 21 Micron Dust Feature , 1999 .

[22]  A. Whitford.  The law of interstellar reddening. , 1958 .

[23]  H. M. Lee,et al.  Optical properties of interstellar graphite and silicate grains , 1984 .