1 / 28

The Elusive Nature of (early) R-stars

The Elusive Nature of (early) R-stars. Inma Domínguez. Tangata: L. Piersanti O. Straniero (INAF-OACT) C. Abia O. Zamora (UGR) R. Cabezón D. García-Senz (UPC). 10th Torino Workshop on AGB Nucleosynthesis: from Rutherford to Beatrice Hill Tinsley and beyond

duaa
Télécharger la présentation

The Elusive Nature of (early) R-stars

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 Elusive Nature of (early) R-stars Inma Domínguez Tangata: L. Piersanti O. Straniero (INAF-OACT) C. Abia O. Zamora (UGR) R. Cabezón D. García-Senz (UPC) 10th Torino Workshop on AGB Nucleosynthesis: from Rutherford to Beatrice Hill Tinsley and beyond January, 25-29, 2010 Chistchurch, New Zealand

  2. Observed properties • Low Luminosities ~ LC(N)/ 10 • Teff: 3800 – 4600 K C(N)  3500 K R-cool R-hot Not on the AGB  Core He-burning NIR C(N) R-cool • Not in Binary systems McClure 1997 (30% of  in binaries)  Previous merger R-hot Zamora et al. 2009

  3. [M/H]: 0  - 0.77 C/O: 0.8  3 12C/13C: 5  20 [N/Fe]: 0.1  1 (Li) : 0.5  1 No s-elements enhancement No evidence of O-depletion R-hot Chemical properties Li R-hot R-cool R-cool • He-burning & CN cycle Zamora et al. 2009

  4. Dominy 1984 Zamora et al. 2009 Chemical properties • Peculiar He-flash in a low mass RG  • Peculiar = mixing But NOT in the standard He-flash !! Most  do not modify their surface composition at the He-flash Dearborn et al. 2006 Lattanzio et al. 2006 Mocak et al. 2008-2009 Confirm by 3D HYDRO

  5. Carbon D-up Like 3-Dup / H-shell extinguishes X neutrinos “ad hoc” 0.4 M 0.4 M Angelou & Lattanzio 2008 Time Paczynski & Tremaine 1977 Increasing core-cooling by axions Domínguez et al. 1999 Increasing core-cooling by neutrinos But All  !! 12C/13C  !!

  6. Internal rotation in low mass stars Mengel & Gross, 1969 A series of flashes occurring progressively closer to the center NO MIXING Mfl  w min for w = 0.16 rad/s NO mixing !! Merger  Rotation

  7. Merger scenario: binary synthesis population Izzard et al. 2007 Number and location in the Galaxy of observed R-stars Dominant channel at [M/H] ~ 0  RG + He WD • Very common in nature Not studied in detail before 2 He WDs Iben 1990 (no rotation) Guerrero et al. 2004 (SPH) • Merging  Rotation  Different physical structure !!

  8. Selectingthe models RG + He WD (70 %) MRGcore 77 % 23 % too luminous !! (core mass ) Izzard et al. 2007

  9. Numerical Simulations Phases in the merging scenario: • Coalescence– Common envelope phase • Merging itself – Accretion disk around degenerate core • Accretion – Mass deposition onto the He core • 3D Hydrodynamical simulations - SPH: Merging • FRANEC: structures & accretion phase & evolution Coalescence (Population Synthesis) MRG : 1.4 1.3 1.2 MRGcore: 0.19 0.20 0.17 MWD: 0.2 0.15 0.38 Mfin : 0.76 0.75 0.78 Mcore: 0.5 0.36 0.55 A (R) : 20 20 16 masses in M Piersanti et al. 2010 (submitted)

  10. MWD = 0.15 M MRG_core = 0.2 M SPH RG 50000 WD 37000 resolve 104 in  SPH based on Monaghan 2005

  11. High accretion rates: 10-6 - 10-4 M /second • High angular velocities: core rigid rotation  ~ 0.036 rad/s • No He-burning (artificial viscosity ??) Tmax ~ 1.6 108 K  ~ 5280 g/cm3 nuc  hyd • in 2 hours Keplerian disk  evol. time-scales long

  12. FRANEC: accretion phase & evolution Accretion – Mass deposition onto the He core 10-5 M /yr (Eddington limit) Assume: inner core & expanded envelope decoupled (different time-scales, presence of the accretion disk) masses in M MRG : 1.4 1.3 1.2 MRGcore: 0.19 0.20 0.17 MWD: 0.2 0.15 0.38 Mfin : 0.76 0.75 0.78 Mcore: 0.5 0.36 0.55 Piersanti et al. 2010 (submitted) Different assumptions: • Angular momentum deposited by the accreted matter • Angular momentum transport efficiency into the accreting He-core No-rotation Rigid-rotation Differential-rotation

  13. After accretion During accretion 10-5 M /yr NO He-burning He-ignition No rotation acc << dif central ignition Diff. rotation 0. 0.1 0.2 0.3 0.4 0.5 M/M 0. 0.1 0.2 0.3 0.4 0.5 M/M Piersanti et al. 2010

  14. After accretion  H-burning active  No mixing Differential rotation No rotation Rigid rotation 104 107 109 100 100 0.6 0.4 0.5 0.1 0.1

  15. Accretion is the main physical mechanism driving the evolution of the  inner core & expanded envelope decoupled acc << diff compression  local T  No He-burning • After accretion – evolutionary time-scales longer thermal energy diffuses inward  whole core T  (less degenerate) re-ignition of H-burning shell He-ignition closer to the center He-flash less strong • Rotation “modulates” that behaviour: T    MHe-core  vs standard single RGB No-rotrig-rotdif-rot MHe 0.400.410.47 Mig 0.12 0.04 0.00 Mf 0.24 0.36 0.45 bigger If MHeWD  ?? inner

  16. “massive” He-WDs ? RG + He WD MRGcore Number is OK 77 % 23 % Zamora et al. 2009 40% of the sample wrongly classified too luminous !! (core mass ) Izzard et al. 2007

  17. MWD =0.38 M MRG =1.20 M (MRGcore =0.17 M) • At the end of accretion • TMAX = 1.28 108 K BUT • = 6500 g/cm3 Mild He-flashes within He-core Mild flashes For MWD  weak He-flashes Isolated by accretion disk Piersanti et al. 2010

  18. Merging of a RG + He-WD in common envelope • is very common in nature (Izzard et al. 2007) • We have studied the final outcome: • Physical structure very different from standard single RGB (T,  and rotation) • physical conditions do not favour external or stronger He-flashes • NO mixing of C-rich material into the envelope • (early) R-stars progenitors still missing

  19. C-rich RR Lyrae Tohunga !!! Wallerstein et al. 2009 Mixing at the He-flash ?? Wallerstein et al. 2009 [Fe/H] [C/Fe] [N/Fe] [O/Fe] C/O KP Cyg + 0.18 0.52 0.90 -0.07 1.7 UY CrB - 0.40 0.65 1.26 + 0.59 0.83 R-hot -0.28 0.53 0.60 (?) 1.6 No s-elements • 12C from He-burning • 13C from proton captures over 12C • 14N from proton captures over 13C H mixes with 12C (Pop. III) How ??

  20. The Nature of (early) R-stars ?? Te Araroa (long way) runangaka pai (Excellent meeting) Kia Ora (Good luck/Good health)

  21. The Nature of R-stars ??still Elusive Te Araroa (long way) runangaka pai (Excellent meeting) Kia Ora (Good luck/Good health)

  22. Population III stars • He-convective zone into H-rich layers • H-ingestion • Two convective shells • Convective envelope into N and C-rich regions 12C/13C C-rich N-rich Hollowell, Iben, Fugimoto, 1990 Picardi et al. 2004 Cristallo et al. 2007 Schlattl et al. 2002 D-up H-ingestion He-ignition close to H/He H-shell less efficient  Lack of CNO elements

  23. 2 He-WDs of MWD = 0.4 M The maximum temperature  thermonuclear flash Tmax = 2 108 K Tmax = 1.6 108 K Guerrero, García-Berro, Isern, 2004

  24. Rotation Differential Rigid

  25. No rotation

  26. Galactic distribution

  27. Galactic distribution

More Related