1 / 31

The synthesis of 26 Al and 60 Fe in massive stars and their current abundances in our Galaxy

The synthesis of 26 Al and 60 Fe in massive stars and their current abundances in our Galaxy. Alessandro Chieffi Istituto Nazionale di AstroFisica (Istituto di Astrofisica Spaziale e Fisica Cosmica) & Centre for Stellar and Planetary Astrophysics – Monash University - Australia

mercer
Download Presentation

The synthesis of 26 Al and 60 Fe in massive stars and their current abundances in our Galaxy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The synthesis of 26Al and 60Fe in massive stars and their current abundances in our Galaxy Alessandro Chieffi Istituto Nazionale di AstroFisica (Istituto di Astrofisica Spaziale e Fisica Cosmica) & Centre for Stellar and Planetary Astrophysics – Monash University - Australia Email: alessandro.chieffi@iasf-roma.inaf.it In collaboration with Marco Limongi

  2. SMM GRIS Between 1979 and 2001 several experiments were carried out: CGRO HEAO3 R. DIEHL Clemson 2005 Astronomy with Radioactivities V Kretschmer et al. AA 412,47 (2003)

  3. On the basis of just the integrated flux towards the galactic center, it is not possible to choose among the various possible 26Al sources: 10<M<30 Type II Supernovae Confined in the spiral arms of our Galaxy 30<M<120 WR stars Novae Confined within the disk of our Galaxy 1-3<M<7 Intermediate mass stars

  4. Kretschmer et al. AA 412,47 (2003) Plüschke et al. AIP Conf. Proc. 510 ed. M.L. McConnell & J.M. Ryan p 35-39 (2000)) 1.809 MeV All Sky Map CGRO

  5. The 53 GhZ free-free all-sky map marks the regions of ionized matter. A strong ionizing flux (l<912 A) is necessary to mantain matter ionized (otherwise it would recombine in 1 Myr) Only stars more massive than, say, 15 MO do produce a strong ionizing flux hence The correlation between the 53 GhZ free-free and the 1.809 MeV maps implies that they share the same spatial distribution amd therefore that 26Al and ionizing photons are produced by the same stars i.e. 26Al mainly produced by stars more massive than 15 MO Knodelseder (1999 - ApJ 510, 915) found also that the scaling between the two fluxes is CONSTANT towards all longitudes and equal to: Y26Al = 10-4 MO per O7 V (Log(Qo)=49.05) RGxL = 1.25 10-11 g1.8MeV / g<912A

  6. RHESSI and INTEGRAL launched in 2002 Reuven Ramaty High Energy Solar Spectroscopic Imager INTErnational Gamma-Ray Astrophysics Laboratory R. DIEHL Clemson 2005 Astronomy with Radioactivities V R. DIEHL Clemson 2005 Astronomy with Radioactivities V 60Fe/26Al RHESSI 0.17± 0.05 INTEGRAL 0.11± 0.03 Diehl et al. (2006 – Nature 439,5)

  7. Summary of the observational facts: 1) 26Al is very probably produced by stars having M>15 MO 2) There are roughly 1.25 10-11g1.8MeV per ionizing photon at all longitudes 3) The 60Fe/26Al flux ratio is of the order of 0.14 ± 0.05 towards the Galactic center 4) Roughly 2.8 MO of 26Al are present in the Galaxy (± 30%)

  8. The present data have been extracted from our latest database of evolutions of massive stars: Limongi and Chieffi (2006 – ApJ 647, 483) & Chieffi and Limongi (2007 – in preparation) FRANEC (release 5.050419) O.R.F.E.O. Online Repository for the Franec Evolutionary Output WEBPAGE: http://orfeo.iasf-roma.inaf.it Main changes with respect to our previous models: 1) Very extended mass range => 11 < M/MO < 120 2) Mass Loss included (full WR phases taken into account) 3) updated cross sections 4) Mixing performed through the diffusion formalism 5) Mixing and burning fully coupled together and solved simultaneously WARNING: though the ground and the metastable 26Al states are properly taken into account, for simplicity in the following I’ll simply refer to the total 26Al

  9. H rich mantle Central H burning He burning shell He core C convective shell CO core Fe Shock wave Si burning shell 26Al production: 1) H convective core 2) C (Ne/C) conv. shell (when the star is in shell Si burning) 3) Explosive Ne burning

  10. H rich mantle Central H burning 26Al production in central H burning 28Si 29Si 26Al 27Al P 24Mg 25Mg 26Mg N The 25Mg is the initial one (usually scaled solar)

  11. He core CO core Fe DESTRUCTION: C profile X produced preserved 26Al 22Ne,12C M 26Al production in the C (Ne/C) convective shell 28Si 29Si 26Al 27Al P 24Mg 25Mg 26Mg N

  12. 26Al production in C (Ne/C) convective shell

  13. He core CO core 28Si 29Si Fe 26Al 27Al P (n,p) 24Mg 25Mg 26Mg T2 23Na T1 N Fe core r1 r2 Shock wave ignition 26Al production by the explosive Ne burning The synthesis of 26Al occurs in the region where the peak temperature drops to Tpeak» 2.2 109 K

  14. Total 26Al yield as a function of the initial mass

  15. Summary of the observational facts: 1) 26Al is very probably produced by stars having M>15 MO 2) There are roughly 1.25 10-11g1.8MeV per ionizing photon at all longitudes 3) The 60Fe/26Al flux ratio is of the order of 0.14 ± 0.05 towards the Galactic center 4) Roughly 2.8 MO of 26Al are present in the Galaxy (± 30%)

  16. By adopting: mup’ =11MO – Mtop = 120MO a Galactic Lyman continuum Luminosity QGAL= 3.5 1053 photons/s The galactic RGxL The galactic 26Al

  17. The galactic 26Al By adopting: mup’ =11MO – MSN I I =35MO – Mtop = 120MO a Galactic Lyman continuum Luminosity QGAL= 3.5 1053 photons/s Steady state

  18. g2 Velorum Binary system containing the closest WR(11) star Main data taken from Schaerer et al. (1997) and Oberlack et al. (2000) Distance: 258 pc - WC8 (9 MO) - O8.5III (29 MO) 26Al(Upper limit) => 6.3 10-5 (+2.1-1.4) MO

  19. g2 Velorum Binary system containing the closest WR(11) star Main data taken from Schaerer et al. (1997) and Oberlack et al. (2000) Distance: 258 pc - WC8 (9 MO) - O8.5III (29 MO) 26Al(Upper limit) => 6.3 10-5 (+2.1-1.4) MO

  20. 60Fe production: 1) basics 60Ni 58Ni 61Ni 62Ni 59Co P 56Fe 57Fe 58Fe 60Fe 59Fe 44 d N 22Ne(a,n)25Mg Main n donor Central He burning rcrit = 1010 n/cm3 r < 107 n/cm3 T < 3.5 108 K r = few 107 n/cm3 rcrit = 3 1011 n/cm3 Central C burning T < 109 K r => 6 1010 to 1012 n/cm3 Shell He burning T > 4 108 K r => 6 1011 to 2 1012 n/cm3 Shell C burning T > 1.3 109 K r => 6 1011 to 2 1012 n/cm3 Shell Ne burning T > 1.8 109 K

  21. He/C X produced preserved 60Fe 22Ne,12C M 60Fe production: 2) the He and C convective shells

  22. 60Fe production: 3) the Ne explosive contribution

  23. The total60Fe production M < 60 MO Mainly produced by the C convective shell M > 60 MO Mainly produced by the C convective shell (Ledoux criterion) M > 60 MO Mainly produced by the He convective shell (Schwarz. criterion)

  24. The galactic 60Fe/26Al flux ratio The 60Fe/26Al flux ratio is of the order of 0.14 ± 0.03 towards the Galactic center

  25. Summary & Conclusions • Observational: • 26Al is very probably produced by stars having M>15 MO • There are roughly 1.25 10-11 n(g1.8MeV)/ (ionizing photon) at all longitudes • The 60Fe/26Al flux ratio is of the order of 0.14 ± 0.05 towards the Galactic center • Roughly 2.8 MO of 26Al are present in the Galaxy (± 30%) • Theoretical: • 26Al is mainly produced by the Ne explosive burning. • 60Fe is mainly produced by the C convective shell. • The observed (and quite constant) average number of g1.8MeV per ionizing photon (RGxL) is rather well reproduced by our models. • The observed 60Fe/26Al flux ratio towards the center of our Galaxy is well reproduced if the Langer (1989) mass loss rate in the WNE,WCO is adopted. • Our predictions for g2 Velorum are in agreement with the quoted upper limit and hence the longstanding discrepancy between the data and the predictions is removed.

More Related