Stellar evolution and the ‘O-rich AGB sequence’

F. Jiménez-Esteban1,2,

P. García-Lario2 & D. Engels1

1- Hamburger Sterwarte / Universität Hamburg

2- ISO Data Center / European Space Astronomy Center

Well defined location of O-rich AGB stars in the IRAS c-c diagram

Sequence of increasing optical thickness of the CSE:

3 possible interpretations:

- Evolutionary

- Progenitor mass

- Combination of both

AGB PN

Stellar evolution and the ‘O-rich AGB sequence’The ‘O-rich AGB sequence’

van der Veen & Habing, 1988, A&A, 194, 125

Thinner Bluer

Thicker Redder

Stellar evolution and the ‘O-rich AGB sequence’The sample

Two previous photometric analysis of OH/IR stars: I - Arecibo sample - 363 (Jiménez-Esteban et al., 2005, A&A, 431, 779) II - GLMP sample - 94 (Jiménez-Esteban et al., 2005, A&A, submitted)

Samples are not directly comparable, but complementary:

i) Arecibo: blue colours GLMP: red colours

ii) Arecibo: Arecibo sky GLMP: the entire sky (32% of GLMP in the GB)

457 OH/IR stars providing very good coverage

Stellar evolution and the ‘O-rich AGB sequence’Bolometric Flux

Well covered Spectral Energy Distribution J-H-K ( own obs. or 2MASS ); A-C-D-E ( MSX ); 12-25-60-100 ( IRAS ) (1.25 - 1.65 - 2.2 m ) (8.28 - 12.13 - 14.65 - 21.3 m )

Integration: trapezium rule + Extrapolation Fbol

Stellar evolution and the ‘O-rich AGB sequence’Absolute bolometric luminosity

41 GLMP OH/IR in the direction of the Galactic Bulge D 8kpc

bol

2bol FD4L

Wide range 2500 – 26000 L

Maximum in 3500 L

Coincidence with other

authors who studied mainly bluer samples of OH/IR stars in the GB and in the solar neighborhood

We assume LOH/IR 3500 L

Distance & Galactic Height

( Habing et al. 1985; Rowan-Robinson & Chester 1987; Jones et al. 1994; Blommaert et al. 1998; Wood et al. 1998; Jackson et al. 2002; Knauer et al. 2001 )

The luminosity function may be similar throughout theGalaxy and not very dependent on the colours

Stellar evolution and the ‘O-rich AGB sequence’Parametrization

[12] –[25] adequate descriptor for the blue part of the sequence

[25] –[60] adequate descriptor for the red part of the sequence

We parameterize the curve:

0,72-2,42[60]-[25]

Ln0,912[25]-[12]

Lower λ BluerHigher λ Redder

Stellar evolution and the ‘O-rich AGB sequence’Galactic Height

Relation between and the galactic height

red OH/IR stars are concentrated towards the Galactic Plane

The red part of the O-rich AGB sequence mustbe populated mainly with objects of higher mass

Stellar evolution and the ‘O-rich AGB sequence’Expansion velocity

Deficit of OH/IR stars with high vexp at large GH

Systematic trend: high vexp

in OH/IR stars with small GH

Low vexp associated to low

High associated to high vexp

Low OH/IR stars covers the whole range of vexp

The red part of the O-rich AGB sequence is mainly populated by high progenitor mass and high Vexp stars

The blue part of the O-rich AGB sequence is populated by OH/IR stars with a wide range of Vexp and progenitor masses

Stellar evolution and the ‘O-rich AGB sequence’Evolutionary Scenario

Evolutionary ScenarioAll OH/IR stars would start the AGB phase, independent of their progenitor mass, in the blue part of the O-rich AGB sequence, and

then they would evolve toward redder colors, although only the more massive stars would reach the red end of the O-rich AGB sequence.

Stellar evolution and the ‘O-rich AGB sequence’Galactic Scale Height

H

Z

e

0NZ N

∆ = 0.3

Galactic scale height ( H ):

Range

N of stars

H( pc )

Ext. blue 0.6 43 536

Blue 0.6 < 1.2 193 344

Transition 1.2 < 1.8 58 287

Red 1.8 < 3.0 66 193

Ext. red 3.0 < 22 48

Thin CSE

Thin & Thick CSE

Thick CSE

Stellar evolution and the ‘O-rich AGB sequence’Evolutionary connection

Extremely blue ( H = 536 pc )Optical Miras with short-P ( H = 600 pc )(Jura 1994)

Type III PN ( <Z> = 660 pc )(Maciel & Dutra 1992)

Blue ( H = 344 pc )Solar neighbourhood OH/IR ( H = 330 pc )(Ortiz & Maciel 1996)

Miras close to the Galactic Plane ( H = 315 pc )(Wood & Cahn 1977)

Type II PN ( <Z> = 350 pc )(Maciel & Dutra 1992)

Stellar evolution and the ‘O-rich AGB sequence’

Transition ( H = 287 pc )Intermediate- and long-P Miras ( H = 240 pc )(Jura & Kleinmann 1992)

Optical C-rich stars ( H = 290 - 260 pc )(Groenewegen et al. 1992)

( Massive ) Type II PN ( 250 < <Z> < 350 pc )

Red ( H = 193 pc )IR C-stars ( H = 155-200 pc )

(Groenewegen et al. 1992; Claussen et al. 1996)

O-rich HBB AGB stars (N-rich)Type I PN ( <Z> = 150 pc )

(Maciel & Dutra 1992)

Extremely red ( H = 48 pc )Infrared PN? ( OHPNe )

Evolutionary connection

Stellar evolution and the ‘O-rich AGB sequence’Conclusions

Unique sample of ~450 OH/IR to study the O-rich AGB sequence

Found a triple relation among Progenitor mass - - vexp

Postulated an evolutionary scenario which need to be further investigated

Defined 5 main groups and established evolutionary connections

between all kind of AGB stars and PNe

Stellar evolution and the ‘O-rich AGB sequence’