S-Process in low metallicity Pb stars: comparison between new theoretical results and spectroscopic observations Sara Bisterzo (1) Roberto Gallino (1),

s-Process in low s-Process in low metallicity Pb stars: metallicity Pb stars: comparison between new comparison between new theoretical results and theoretical results and

spectroscopic observationsspectroscopic observations Sara Bisterzo Sara Bisterzo (1)(1)

Roberto Gallino Roberto Gallino (1)(1), Oscar Straniero , Oscar Straniero (2)(2), I. I. Ivans , I. I. Ivans (3, 4)(3, 4),, F. Käppeler F. Käppeler (5)(5)

andandWako Aoki, Sean Ryan, Timoty C. BeersWako Aoki, Sean Ryan, Timoty C. Beers

(1)(1) Dipartimento di Fisica Generale , Università di Torino, 10125 (To) Italy Dipartimento di Fisica Generale , Università di Torino, 10125 (To) Italy(2) (2) Osservatorio Astronomico di Collurania – Teramo, 64100Osservatorio Astronomico di Collurania – Teramo, 64100

(3)(3)The Observatories of the Carnegie Institution of Washington, Pasadena, CA, (USA) The Observatories of the Carnegie Institution of Washington, Pasadena, CA, (USA) (4)(4)Princeton University Observatory, Princeton, NJ (USA)Princeton University Observatory, Princeton, NJ (USA)

(5)(5)Forschungszentrum Karlsruhe, Institut für Kernphysik, D-76021 Karlsruhe, GermanyForschungszentrum Karlsruhe, Institut für Kernphysik, D-76021 Karlsruhe, Germany

VIII Torino Workshop, Granada, 6 – 11 Febr. 2006

Outline:Outline:

Lead stars (C, s, Pb rich)Lead stars (C, s, Pb rich) C and C and s+r richs+r rich Lead stars Lead stars s-enhanced stars and Pb predictionss-enhanced stars and Pb predictions Nb: indicator of an extrinsic AGB in a Nb: indicator of an extrinsic AGB in a

binary systembinary system Na (and Mg): permits an estimate of Na (and Mg): permits an estimate of

the initial AGB stellar mass.the initial AGB stellar mass.

AGB models at AGB models at very low very low [Fe/H][Fe/H]

M = 1.5 Msun

1.2 Msun < M < 3 Msun

13C-pocket: ST*2 …. ST/100 Constant pulse by pulse(ST: 4.10-6 Msun , [Fe/H] = -0.3, Reproduction of Solar Main Component )

1.2 Msun 3 pulses 1.3 Msun 6 pulses1.4 Msun 8 pulses1.5 Msun 20 pulses2 Msun 26 pulses3 Msun 30 pulses

Mass loss : from 10-7 to 10-4 Msun/yr Reimers

1.2 Msun η = 0.3 1.3 Msun η = 0.31.4 Msun η = 0.31.5 Msun η = 0.32 Msun η = 0.53 Msun η = 1

Extrinsic AGB modelsExtrinsic AGB models

Diluition factor: used to simulate the mixing effect in the envelope of the extrinsic stars

)(

)(log

transfM

obsMdil

AGB

star

Note: for main sequence stars dil ≈ 0 for giants dil may be important

[ls/Fe] versus [ls/Fe] versus [Fe/H] [Fe/H]

ls = <Y, Zr>ls = <Y, Zr> M = 1.3 MΘ

M = 1.5 MΘ

M = 2 MΘ

M = 3 MΘ

3

2

1

3

2

1

3 3

2 2

Example: ST/12 at [Fe/H] = -2.5

[hs/ls] versus [hs/ls] versus [Fe/H][Fe/H]

1

0

1

1 1

0

-1 -1

0

M = 1.3 MΘ M = 1.5 MΘ

M = 2 MΘ M = 3 MΘ

Example: ST/2 at [Fe/H] = -2

0

[hs/ls] for different masses [hs/ls] for different masses at [Fe/H] = -2.6at [Fe/H] = -2.6

1.5 dex 1 dex

[Pb/hs] versus [Fe/H][Pb/hs] versus [Fe/H]

To reproduce stars with both s+r To reproduce stars with both s+r enhancementsenhancements

Different choice of initial chemical abundances of Eu in the progenitor clouds [Eu/Fe]ini from 0.5 to 1.5 and 2.0

Effect of pre r-enrichment in s-enhanced stars

Model with pre r-enrichment normalized to [Eu/Fe]ini = 2.0 in the parental cloud: the envelope abundances in these stars are predicted by mass transfer from the more massive AGB companion in a binary system which formed from a parental cloud already enriched in r elements.

r-process rich

AGB star model of M = 1.3 Msun with [Fe/H] = - 2.60.

NO r-process rich

[Eu/Fe]ini = 2.0[Eu/Fe]ini = 0.0

Choice of initial abundances

The choice of the initial r-rich isotope abundances normalised to Eu is made considering the r-process solar prediction from Arlandini et al.1999.

1- Lead stars (C, s, Pb 1- Lead stars (C, s, Pb rich)rich)

2 – C and 2 – C and s+r richs+r rich Lead Lead starsstars

1. J. A. Johnson, M. Bolte, ApJ 579, L87 (2002) 2. W. Aoki, et al., ApJ 580, 1149 (2002) 3. T. Sivarani, et al., A&A 413, 1073 (2004) 4. J. A. Johnson, M. Bolte, ApJ 605, 462 (2004) 5. W. Aoki, et al., PASJ 54, 427 (2002) 6. S. Van Eck et al., A&A 404, 291 (2003)

7. S. Lucatello, et al., AJ 125, 875 (2003) 8. J. G. Cohen et al., ApJ 588, 1082 (2003)9. B. Barbuy, et al., A&A 429, 1031 (2005) 10. I. Ivans et al., ApJ 627, 145 (2005) 11. K. Jonsell et al., astroph 1476J (2006)

Teff = 5850

CS 22880-074 Aoki et al. CS 22880-074 Aoki et al. 20022002

HE 0024-2543 Lucatello et al. 2003

Teff = 6625

2 – C and s+r rich Lead stars2 – C and s+r rich Lead stars

0.0

Without r-process enhancement [Eu/Fe] ini = 0.0

With r-process enhancement [Eu/Fe] ini = 2.0

HE2148-1247 Cohen et al. 2003

M ≈ 1.3 Msun

M ≈ 1.3 Msun

Teff = 6380 K

With r-process enhancement [Eu/Fe] ini = 2.0

Teff = 6160

Jonsell et al. 2006 astroph

CS29497-34 Barbuy et al. 2005With r-process enhancement [Eu/Fe] ini = 1.5

Teff = 4800

CS31062-050 Aoki et al. 2002

With r-process enhancement [Eu/Fe] ini = 1.8

Teff = 5600

Barklem et al. 2005: s-Barklem et al. 2005: s-enhanced starsenhanced stars

** Pb predictions

12. Barklem et al., A&A 439, 129 (2005)

HE 1105+0027 Barklem HE 1105+0027 Barklem et al. 2005et al. 2005

Teff = 6132

Pb prediction 3

With r-process enhancement [Eu/Fe] ini = 1.8

HE 2150-0825 Barklem HE 2150-0825 Barklem et al. 2005et al. 2005

Teff = 5960Pb prediction 3.5

Without r-process enhancement

[Pb/Fe] versus [Fe/H] [Pb/Fe] versus [Fe/H]

[Pb/hs] versus [Pb/hs] versus [Fe/H] [Fe/H]

AGB modelsof M = 1.3, 1.5, 3 Msun, for the same 13C-pocket, at [Fe/H] = – 2.60. A strong primary production of 22Ne results in advanced pulses, by conversion of primary 12C to 14N in the H-burning ashes, followed by 2a captures on 14N in the thermal pulses and implies a primary production of 23Na via 22Ne(n,)23Na, (and 23Na(n,)24Na(-)24Mg).

Spectroscopic Na (and Mg) Spectroscopic Na (and Mg) Stellar Mass Stellar Mass predictionprediction

The s elements enhancement in low-metallicity stars interpreted by mass transfer in binary systems (extrinsic AGBs). For extrinsic AGBs [Zr/Nb] ~ 0. Instead, for intrinsic AGBs [Zr/Nb] ~ 1.

Zr over Nb: Intrinsic or Extrinsic AGBs

s-process path

CONCLUSIONS:CONCLUSIONS:The spectroscopic abundances of low-The spectroscopic abundances of low-

metallicity s- and r-process enriched stars metallicity s- and r-process enriched stars are interpreted using theoretical AGB are interpreted using theoretical AGB models (FRANEC CODE),models (FRANEC CODE), with an initial with an initial composition already enriched in r elements composition already enriched in r elements from the parental cloud from which the from the parental cloud from which the binary system was formed.binary system was formed.

[Zr/Nb] is an indicator of an extrinsic AGB in [Zr/Nb] is an indicator of an extrinsic AGB in a binary system: [Zr/Nb] ~ 0 for an extrinsic a binary system: [Zr/Nb] ~ 0 for an extrinsic AGB, [Zr/Nb] ~ AGB, [Zr/Nb] ~ –– 1 for an intrinsic AGB. 1 for an intrinsic AGB.

Spectroscopic determination of [Na/Fe] and Spectroscopic determination of [Na/Fe] and [Mg/Fe] permits an estimate of the initial [Mg/Fe] permits an estimate of the initial AGB stellar mass.AGB stellar mass.

CONCLUSIONS:CONCLUSIONS: Open ProblemOpen Problem: the strong discrepancy of C : the strong discrepancy of C

and N predictions with respect to and N predictions with respect to observations may be reconciled:observations may be reconciled:

(1)(1) by introducing the effect of cool bottom by introducing the effect of cool bottom process (CBP) in the TP-AGB phase (*);process (CBP) in the TP-AGB phase (*);

(2)(2) for N and [Fe/H] < -2.3, by the effect of for N and [Fe/H] < -2.3, by the effect of Huge First TDU.Huge First TDU.

(3)(3) Uncertainties in the spectroscopic Uncertainties in the spectroscopic abundances of C, N, O, Na, Mg abundances of C, N, O, Na, Mg M. M. Asplund, ARAA 2005Asplund, ARAA 2005

(*) Nollett, K. M., Busso, M., Wasserburg, G. J., ApJ 582, 1036 (2003);Wasserburg, G. J., Busso, M., Gallino, R., Nollett, K. M., (2006), Nucl. Physics, in press.

[hs/Fe] versus [hs/Fe] versus [Fe/H][Fe/H]

hs = <Ba, La, Nd, Sm> hs = <Ba, La, Nd, Sm> M = 1.3 MΘ

M = 1.5 MΘ

M = 2 MΘ M = 3 MΘ

3 3

3 3

2

2

2

2

1

1

1

1