Stellar evolution in the post-AGB stage Olga Suárez Laboratorio de Astrofísica Espacial y Física Fundamental – Madrid (Spain) Supervisors: Minia Manteiga Outeiro Pedro García Lario Or... “An optical catalogue of post-AGB candidates” I n colaboration with: Arturo Manchado, Ana Ulla, S.R. Pottasch

Objectives i Study of stars in the transition phase from AGB to PN. v Catalogue - large number of objects v Multiwavelength study - SEDs v Use of statistical tools

Objectives i Study of stars in the transition phase from AGB to PN. v Catalogue - large number of objects v Multiwavelength study - SEDs v Use of statistical tools

Stellar evolution

Post-AGB evolution (Blöcker, 1995)

Nomenclature used in this work i Post-AGB: AGB mass loss has ceased. not ionized envelope i Transition objects: stellar continuum forbidden lines (no [OIII]) i Planetary Nebula (PN): no stellar continuum forbidden lines

The catalogue - Selection criteria i IRAS colours: H [12] – [25] =  2.5  log (F 12  m /F 25  m ) H [25] – [60] =  2.5  log (F 25  m /F 60  m ) i Flux ratios: v F 12  m /F 25  m  0.50 v F 25  m /F 60  m  0.35 v F 60  m /F 100  m  0.60 i Low IRAS variability  to avoid AGBs

The catalogue in the IRAS c-c diagram

The catalogue - spectroscopic observations

The catalogue - imaging observations

The catalogue - the search Hα - contHα

The catalogue - the search

IRAS [NII] Hα Riera et al., RevMexAA, 2003 Suárez et al., in preparation

The catalogue - number of objects i 255 observed objects I 104 post-AGB stars (with optical spectra) I 21 transition objects I 36 Planetary Nebulae I 3 AGB stars I 38 young stellar objects or HII regions I 2 Seyfert galaxies I 5 peculiar stars I 47 objects without optical counterpart (42 believed to be obscured post-AGB stars)

The catalogue - a sample

Analysis of the spectra i Spectral classification of post-AGB stars and young stellar objects. v Comparison with catalogues (Silva, 1992; Pickles, 1998; Jacoby, 1984) Wavelength Relative flux

Analysis of the spectra i Excitation classes for PNe (Morgan, 1984; Dopita, 1990; and Crowther, 1998) v Based on strength line ratios.

Analysis of the spectra

Spectral Energy Distributions i Data from optical spectra, 2MASS, MSX, IRAS. i Classification according to van der Veen et al. (1989) Class IClass IIClass III Class IVaClass IVb

IRAS colour-colour diagram i Models by van Hoof et al. (1997), based on Blöcker (1995), show the evolution in this diagram.

IRAS colour-colour diagram

Conclusions i Observations - selection criteria based on IRAS colours i Catalogue sources: 104 post-AGB stars, 21 transition objects, 36 PNe. i Spectra and SEDs classified - multiwavelength analysis using statistical tools

Galactic latitude distribution i Statistical indicator of the mass of a population of stars. v High latitude (wide galactic latitude distribution)  lower mean mass v Low latitude (narrow galactic latitude distribution)  higher mean mass

Results i Evolutionary status + Galactic latitude + statistics Objects without optical counterpart are obscured post-AGB stars similar to those not observed Post-AGB stars and PNe have different galactic latitude distributionfrom obscured post- AGB stars

Conclusions i Observations - selection criteria based on IRAS colours i Catalogue sources: 104 post-AGB stars, 21 transition objects, 36 PNe. i Spectra and SEDs classified - multiwavelength analysis using statistical tools