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53° CONGRESSO SAIT PISA, 4 - 8 MAGGIO 2009

53° CONGRESSO SAIT PISA, 4 - 8 MAGGIO 2009. SN 2008ha and SN 2008S: is there a role for the super-asymptotic giant branch stars?. M.L. Pumo INAF - Osservatorio Astronomico di Padova & INAF – Osservatorio Astrofisico di Catania.

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53° CONGRESSO SAIT PISA, 4 - 8 MAGGIO 2009

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  1. 53° CONGRESSO SAIT PISA, 4 - 8 MAGGIO 2009 SN 2008ha and SN 2008S: is there a role for the super-asymptotic giant branch stars? M.L. Pumo INAF - Osservatorio Astronomico di Padova & INAF – Osservatorio Astrofisico di Catania In collaboration with: M. Turatto, S. Benetti, M.T. Botticella, E. Cappellaro, A. Pastorello, S. Valenti, L. Zampieri

  2. Classification scheme of SNe (e.g. Hillebrandt & Niemeyer 2000; Hamuy 2003; Turatto 2003; Turatto et al. 2007) Adapted from Turatto, LNP, 2003, 598, 21

  3. Uncertainties (e.g. Woosley et al. 2002; Heger et al. 2003; Turatto et al. 2007; Smartt et al. 2008) • Theoretical: uncertainties in modelling stellar evolution and explosion mechanism • Observational: “sparse” direct detections of progenitor stars and non-fully reliable classification of the SN events Nature of the CC-SNe progenitors (i.e. initial mass; stellar structure and composition at the explosion; kind of collapse: iron-CC or not) having the required properties to reproduce the different observational features

  4. Ejecta velocities:~ 2,3·103 km·s-1 Amount of ejected 56Ni: ~ 3-5·10-3 M⊙ Bol. luminosity: ~ 1041 erg·s-1 (at peak) Circumstellar material: NO interaction Signatures of hydrogen features: NO PANEL A Ejecta velocities: ~ 3·103 km·s-1 Amount of ejected 56Ni: ~ 1-2·10-3 M⊙ Bolometric luminosity: ~ 1041 erg·s-1 (at peak) Circumstellar material: interaction Progenitor: star of ~10 M⊙ + “thick” CSM envelope PANEL B SN2008ha & SN2008S • “exotic” scenarios • SN2008ha (e.g. Foley et al. 2009): Accretion Induced Collapse • SN2008S(e.g.Smithetal.2009;Bergeretal.2009):LBVeruptionofastar of ≲15M⊙ • alternative scenario(Valenti at al. 2009; Botticella et al. 2009) electron-capture SN (ec-SN) from super-AGB progenitor

  5. Core collapse ⇓ “weak” SN: explosion ener. ~ 1050 erg ejecta vel. ≲ 3·103 kms-1 ejected 56Ni ~ 2-4 ·10-3 M⊙ EC reactions (on 24Mg, 24Na, 20Ne,20F) MONe ~ 1.375 M⊙ SN2008ha SN2008S SNe triggered by electron-captures (e.g. Miyaji et al. 1980; Nomoto 1984; Kitaura et al. 2006; Wanajo et al. 2009) Stellar structure of super-AGB progenitors having the required properties to reproduce all the observational features

  6. super-AGB stellar models (e.g. Siess & Pumo 2006; Pumo 2006; Siess 2007; Poelarends et al. 2008) The most massive super-AGBs: MONe→ 1.375 M⊙ ec-SN super-AGB AGB super-AGB Adapted and taken from Pumo, 2006, PhD thesis, Catania Univ.

  7. Total stellar mass: core mass + envelope mass M1< M2< M3 Mc1 < Mc2 < Mc3 t1 > t2 > t3 Envelope 1.37M⊙ Core time Different initial mass ⇒ core mass at the end-CB ⇒ time t3 t2 t1 Natural diversity in the optical display of the ec-SNe!

  8. Preliminary results SN2008ha: super-AGB with Mini~ MN SN2008S: super-AGB with Minislightly larger (~ 0.6M⊙) SN2008ha: progenitor with Mini = MN SN2008S: progenitor with Mini = MN+ 0.6M⊙

  9. SN2008S and SN2008ha: ec-SNe from super-AGBs, without resorting to “exotic” scenarios Other transients (NGC300 OT2008-1; M85 OT2006-1) and “faint” SNe (SN2007J; II-P SNe) Comments • Theoretical:existence of ec-SNe from super-AGBs confirmed in more refined future studies • Observational:information deduced from observations not substantially changed by new observational data Other observations are necessary to confirm our hypothesis!

  10. Thank you

  11. AGB: low-mass & intermediate-mass Super-AGB massive Mup Mmas MZAMS (~ 7-9M⊙) (~ 11-13M⊙) Stellar mass & the ZAMS MZAMS < Mup: unable to ignite core C-burn. MZAMS≥ Mmas: able to evolve through all nuclear burning stages

  12. Super-AGB Stars (e.g. Garcia-Berro & Iben 1994 ApJ; Pumo & Siess 2007, ASPCS) After H- & He-burn. →partialdegenerate CO core C-burn. (off-centre) → through a flash Afterflash: • development of a flame that reaches the stellar centre, transforming the CO core into a NeO mixture • C-burn. proceeds outside the core before extinguishing, just leaving H- & He-burn. shell

  13. AGB Super-AGB • Structure is similar to the one of AGB stars, except that their cores are: • more massive (1-1.37M⊙) • made of Ne (15-30%) and O (50-70%) • After completion of C-burn., the core mass increases due to the H-He double burn. shell

  14. Final fate (Nomoto, 1984, ApJ) Mfcore< MEC Mfcore =MEC ~ 1.37 M⊙ collapsing electroncaptures supernovae NeO White Dwarf Neutron star

  15. Mend,2 NeO White Dwarf Mend,1 Neutron Star mass loss so efficient ↓ envelop is lost before the core has grown above ~ 1.37 M⊙ Mend,1 1.37M⊙ Mend,2 Interplay between mass loss and core growth (e.g. Woosley et al. 2002, ARA&A) The minimum initial mass for the formation of a neutron star is usually referred to as MN (transition NeO WD / EC SN)

  16. The C-burning nucleosynthesis 12C(12C,α)20Ne 12C(12C,p)23Na 16O(α,)20Ne 20Ne (~ 0.15-0.35),16O (~ 0.5-0.7), 23Na (~ 0.03-0.05) + p and α available for nucleosynthesis up to 27Al 12C (> 0.015) potential trigger of explosion! ↓ Complete disruption of the star (Gutierrez et al. 2005 A&A)

  17. Nucleosynthesis in the NeO core α particle: 22Ne(α,n)25Mg n: 16O, 20Ne, 23Na, 25Mg → 17O, 21Ne, 24Mg, 26Mg 22Ne(α,)26Mg protons: 26Mg(p,)27Al 23Na(p,α)20Ne 23Na(p,)24Mg

  18. Mini~ Mup Mini~ Mmas Mini < Mmas (3.46·107 yr) (3.50·107yr) (1.67·107 yr) (1.77·107yr) (3.35·107 yr) (3.36·107yr) Second dredge-up features highly depend on Mini Garcia-Berro & co-workers 1994,1996, 1997, 1999 ApJ (Z=0.02)

  19. Second dredge-out Mini value depends on Z and mixing treatment Mini = 9.5 – 10.8M⊙ if Z =10-5 - 0.02 Mini~ 7.5M⊙ with ovsh.

  20. Connessione MN – 2DUP

  21. Evoluzione finale e massa MN

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