stellar evolution in the post-agb stage

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”

In colaboration with: Arturo Manchado, Ana Ulla, S.R. Pottasch

Objectives

Study of stars in the transition phase from AGB to PN.

Catalogue - large number of objects

Multiwavelength study - SEDs

Use of statistical tools

Objectives

Study of stars in the transition phase from AGB to PN.

Catalogue - large number of objects

Multiwavelength study - SEDs

Use of statistical tools

Stellar evolution

Post-AGB evolution

(Blöcker, 1995)

Nomenclature used in this work

Post-AGB: AGB mass loss has ceased. not ionized envelope

Transition objects: stellar continuum forbidden lines (no [OIII])

Planetary Nebula (PN): no stellar continuum forbidden lines

The catalogue - Selection criteria

IRAS colours:

[12] – [25] = 2.5 log (F12m/F25m)

[25] – [60] = 2.5 log (F25m /F60m)

Flux ratios: F12m /F25m 0.50

F25m /F60m 0.35

F60m /F100m 0.60

Low IRAS variability to avoid AGBs

The catalogue in the IRAS c-c diagram

The catalogue - spectroscopic observations

Telescope DatesResolution

(A/ pix)SpectralRange (A)

3.6 m ESO March 1988 3.79 3406-69751.5 m ESO J an. 1989 2.47 4272-68121.5 m ESO Feb. 1989 2.80 4046-69201.5 m ESO J une 1990 3.47 4050-6925

2.5 m INT May 1991 2.813570-52265538-7240

2.2 m CAHA Nov. 1991 2.50 3830-67361.5 m ESO Aug. 1992 2.83 3590-94251.5 m ESO March 1993 3.74 3321-110152.5 m INT J uly 1993 1.48 5376-72691.5 m ESO March 1994 3.74 3285-10980

2.5 m INT Aug. 1994 1.573779-54015570-7195

1.5 m ESO Feb. 1995 3.79 3532-11190

2.5 m INT J une 1995 1.573700-54555488-7255

2.5 m INT Apr. 2001 3.30 3702-74013.6 m ESO J une 2003 5.30 3600-9200

The catalogue - imaging observations

Telescope Dates

3.6 m ESO J une 1990 J KT (La Palma) J uly 1990 0.9 m Dutch March 1994 2.5 m NOT J une 2000 2.5 m NOT May 2001 3.6 m ESO J une 2003

The catalogue - the search

Hα - cont Hα

The catalogue - the search

The catalogue - the search

IRAS 17395-0841

[NII]Hα

Hα

Riera et al., RevMexAA, 2003

Suárez et al., in preparation

The catalogue - number of objects

255 observed objects

104 post-AGB stars (with optical spectra)

21 transition objects

36 Planetary Nebulae

3 AGB stars

38 young stellar objects or HII regions

2 Seyfert galaxies

5 peculiar stars

47 objects without optical counterpart (42 believed to be obscured post-AGB stars)

The catalogue - a sample

The catalogue - a sample

Analysis of the spectra

Spectral classification of post-AGB stars and young stellar objects.

Comparison with catalogues (Silva, 1992; Pickles, 1998; Jacoby, 1984)

Wavelength

Rel

ativ

e fl

ux

Analysis of the spectra Excitation classes for PNe (Morgan, 1984;

Dopita, 1990; and Crowther, 1998) Based on strength line ratios.

Analysis of the spectra

Spectral Energy Distributions Data from optical spectra, 2MASS, MSX, IRAS. Classification according to van der Veen et al. (1989)

Class I Class II Class III

Class IVa Class IVb

IRAS colour-colour diagram

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

IRAS colour-colour diagram

Conclusions

Observations - selection criteria based on IRAS colours

Catalogue - 255 sources: 104 post-AGB stars, 21 transition objects, 36 PNe.

Spectra and SEDs classified - multiwavelength analysis using statistical tools

Galactic latitude distribution

Statistical indicator of the mass of a population of stars.

High latitude (wide galactic latitude distribution) lower mean mass

Low latitude (narrow galactic latitude distribution) higher mean mass

Results 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

Observations - selection criteria based on IRAS colours

Catalogue - 255 sources: 104 post-AGB stars, 21 transition objects, 36 PNe.

Spectra and SEDs classified - multiwavelength analysis using statistical tools