1 / 46

Astrophysical, observational and nuclear-physics aspects of r-process nucleosynthesis

Astrophysical, observational and nuclear-physics aspects of r-process nucleosynthesis. B 2 FH. Part I. T 1/2. s n g. S n. P n. . Karl-Ludwig Kratz. Sinaia, 2012. Some early milestones.

hila
Download Presentation

Astrophysical, observational and nuclear-physics aspects of r-process nucleosynthesis

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. Astrophysical, observational and nuclear-physics aspects of r-process nucleosynthesis B2FH Part I T1/2 sng Sn Pn  Karl-Ludwig Kratz Sinaia, 2012

  2. Some early milestones 1859first spectral analysis of the sun and stars by Kirchhoff & Bunsen“chemistry of the cosmos” 1932 discovery of the previously unknown neutron by Chadwick 1937first systematic tabulation of solar abundances by Goldschmidt 1957fundamental paper on nucleosynthesis by Burbidge, Burbidge, Fowler & Hoyle (B2FH) Rev. Mod. Phys. 29, 547 (1957)

  3. B²FH, the „bible“ of nuclear astrophysics • Historically, • nuclear astrophysics has always been concerned with • interpretation of the origin of the chemical elements from astrophysical and cosmochemical observations, • description in terms of specific nucleosynthesis processes. …55 years ago:

  4. Solar abundance observables at B²FH (1957) „…it appears that in order to explain all the features of the abundance curve, at least eight different types of synthesizing processes are demanded…“ (Suess and Urey, 1956) 1. H-burning 2. He-burning 3. -process 4. e-process 5. s-process 7. p-process 8. x-process 6. r-process neutrons

  5. Neutron-capture paths for the s- and r-processes Neutrons produce ≈75% of the stable isotopes, but only 0.005% of the total SS abundances…. s- and r-abundances today about equal H 30,000 C 10 Fe 1 Au 2·10-7 r-process path (from“Cauldrons in the Cosmos”)

  6. r-Process observables today • Observationalinstrumentation • meteoriticandoverallsolar-system • abundances • ground- andsatellite-basedtelescopeslikeImaging Spectrograph (STIS) atHubble, HIRESatKeck, andSUBARU • recent„Himmelsdurchmusterungen“ • HERES and SEGUE Solar system isotopic Nr, “residuals” T9=1.35; nn=1020 - 1028 Pb,Bi r-process observables CS 22892-052 abundances scaled solar r-process scaled theoretical solar r-process Presolar SiC grains and nano-diamonds e.g. isotopic composition of heavy metals Zr, Mo, Ru, Te, Xe, Ba, Pt Zr Pt Os Pb Cd Ru Ba Nd Sn Sr Ga Pd Dy Mo Gd Er Ge Sm Ce Yb Ir Hf Y Rh La Nb Ag Ho Eu Pr Tb Au Lu Th Tm U Isotopic anomalies in meteoritic samples and stardust Elemental abundances in UMP halo stars

  7. Fit of Nr, from B²FH • „Static“ calculation • assumptions • iron seed(secondary process) • „waiting-point“concept • (global (n,)  (,n) and • ß-flow equilibrium) • instantaneous freezeout Reproduction of Solar system isotopic r-process abundances (mainly from r-only nuclei)

  8. The "waiting-point"concept in astrophysics (1) Rate of n-captures: (1) cross section averaged over Maxwell-Boltzmann velocity distribution to T9 Photodisintegration: (2) Nuclear Saha equation

  9. The "waiting-point"concept in astrophysics (2) Nuclear Saha equation: simplified • high nn "waiting-point" shifted to higher masses • low Sn"waiting-point" shifted to higher masses • low T "waiting-point" shifted to higher masses Equilibrium-flow along r-process path: - governed by β-decays from isotopic chain Z to (Z+1) T1/2 ("w.-p.") ↔ Nr,ʘ

  10. Fit of Nr, from B²FH • „Static“ calculation • assumptions • iron seed(secondary process) • „waiting-point“concept • (global (n,)  (,n) and • ß-flow equilibrium) • instantaneous freezeout • astrophysical conditions explosive He-burning in SN-I • T9 1 (constant) • nn 1024 cm-3 (constant) • r  100 s • neutron source:21Ne(,n) Reproduction of Solar system isotopic r-process abundances (mainly from r-only nuclei)

  11. Seeger, Fowler & Clayton, ApJ 98 (1965) • Speculationsabout r-processscenario: • SN-I (as in B2FH) unlikely • Explosion of massive stars M > 104Mʘ • ConventionalSNe Speculations about various r-process components: "short-time" solution 0.44 s 1.77 s 3.54 s Cycle time: 4.9 s "long-time" solution …however, all components with the same neutron-density of 1024 n/cm3 !

  12. r-Process scenarios since B2FH For long time suspect, that puzzle of r-process site is closely intertwined with puzzle of SN explosion mechanism (see e.g. Reviews by Hillebrandt 1978; Meyer & Brown 1997) …original papers "core-collapse SN", e.g. Bethe & Wilson (1985); Mayle & Wilson (1988, 1991); …first papers "neutrino-driven winds", e.g. Duncan, Shapiro & Wasserman (1986); Woosley & Hoffman(1992); Takahashi, Witti & Janka (1994). …other suggested scenarios: • He-core flashes in low-mass stars • He- and C-shells of stars undergoing SN explosions • Neutron-star mergers • Black-hole neutron-star mergers • Hypernovae • Electron-capture SNe • r-Process without excess neutrons • Gamma-ray bursts • SNe with active-sterile neutrino oscillations • Jets of matter from collapse of rotating magnetized stellar cores …becoming more and more "exotic"

  13. Fit of Nr, from B²FH • „Static“ calculation • assumptions • iron seed(secondary process) • „waiting-point“concept • (global (n,)  (,n) and • ß-flow equilibrium) • instantaneous freezeout • astrophysical conditions explosive He-burning in SN-I • T9 1 (constant) • nn 1024 cm-3 (constant) • r  100 s • neutron source:21Ne(,n) • nuclear physics: Q − Weizsäcker mass formula + empirical corrections (shell, deformation, pairing) • T1/2 – one allowed transition to excited state, logft = 3.85 Reproduction of Solar system isotopic r-process abundances (mainly from r-only nuclei)

  14. Parameter checks Fitting r-process abundances: a nuclear-structure learning effect or discussing the fifth leg of an elephant ? • Do r-abundance deficiencies disappear when changing the nuclear-physics input ? • Can effects of masses (Sn) and T1/2 & Pn be studied separately ? • To what extent is the "waiting-point" assumption valid ? keep it simple !

  15. b-decay freeze-out Nuclear-data needs for the classical r-process • b-decay properties T1/2r-process progenitor abundances, Nr,prog Pn  smoothing Nr,prog Nr,final (Nr,) modulation Nr through re-capture • nuclear masses Sn-values  r-process path / “boulevard” Qb, Sn-values  theoretical b-decay properties, n-capture rates • neutron capture rates sRC + sDC  smoothing Nr,prog during freeze-out in “non-equilibrium” phase(s) • fission modes SF, bdf, n- and n-induced fission  “fission (re-) cycling”; r-chronometers • nuclear structure development • level systematics • “understanding” b-decay properties • - short-range extrapolation into unknown regions

  16. Nuclear masses Over the years, development of various types of mass models / formulas: • Weizsäcker formula • Local mass formulas • (e.g. Garvey-Kelson; NpNn) • Global approaches • (e.g. Duflo-Zuker; KUTY) • Macroscopic-microscopic models • (e.g. FRDM, ETFSI) • Microscopic models • (e.g. RMF; HFB) Comparison to NUBASE (2001) // (2012) FRDM (1995)srms = 0.669 // 0.564 [MeV] ETF-Q (1996) srms = 0.818 // 0.729 [MeV] HFB-2 (2002) srms = 0.674 [MeV] HFB-3 (2003) srms = 0.656 [MeV] HFB-4 (2003) srms = 0.680 [MeV] HFB-8 (2004) srms = 0.635 [MeV] HFB-9 (2005) srms = 0.733 [MeV] HFB-21 (2011) srms = 0.577 [MeV] No significant improvement of srms J. Rikovska Stone, J. Phys. G: Nucl. Part. Phys. 31 (2005) Main deficiencies at Nmagicand in shape-transition regions ! D. Lunney et al., Rev. Mod. Phys. 75, No. 3 (2003)

  17. Nuclear masses effect of Sn around N=82 shell closure catchword “shell-quenching” astrophys. parameters (T9, nn, τn) and T1/2 kept constant “static” calculations (Saha equation) break-out at N=82 130Cd “time-dependent” calculations (w.-p.) r-matter flow at A=130 peak K.-L. Kratz et al. Nucl. Phys. A630 (1998) B. Pfeiffer et al. Nucl. Phys. A693 (2001)

  18. Effects of N=82 "shell quenching" N/Z ) 0 w g 9/2 h 126 g 9/2 of p 1/2 i 7.0 f 13/2 112 5/2 p Units h ;f 3/2 i 9/2 5/2 13/2 p h 1/2 ( 6.5 9/2 f p 7/2 3/2 f 7/2 Energies h 11/2 70 6.0 h 11/2 g d 7/2 3/2 g d 7/2 s 3/2 1/2 5.5 s d 1/2 5/2 50 d 5/2 Single – Neutron g g 9/2 5.0 9/2 40 p 1/2 f 5/2 f p 5/2 1/2 70% 10% 100% 40% Strength of ℓ -Term 2 82 B. Pfeiffer et al., Acta Phys. Polon. B27 (1996) "Shell quenching" …reductionofthespin-orbit couplingstrength; causedby strong interactionbetweenboundandcontinuumstates; due todiffusenessof "neutron-skin" anditsinfluence on thecentral potential… • high-j orbitals  (e.g. nh11/2) • low-j orbitals  (e.g. nd3/2) • evtl. crossing of orbitals • new “magic” numbers / shell gaps • (e.g. 110Zr70, 170Ce112) change of • shell-gaps • deformation • r-process path (Sn) • r-matter flow (τn)

  19. The N=82 shell gap as a function of Z TheN=82shell closure dominates the matter flow of the „main“ r-process (nn ≥ 1023). Definition „shell gap“: S2n(82) – S2n(84) ↷ paired neutrons. Therefore request: experimental masses and reliable model predictions for the respective N=82 waiting-point nuclei 125Tc to 131In A≈130 Nr, peak FRDM Exp DZ Exp Groote EFTSI-Q HFB-14

  20. N=82 shell-quenching FRDM “trough” WARNING:FRDM not appropriate for r-process calculations !

  21. Deviation from SS-r: FRDM vs. ETFSI-Q • How to fill up the FRDM A  115 “trough” ? • if via T1/2 (as e.g. suggested by Nishimura, Kajino et al.; PRC 85 (2012)), on average all r-progenitors between 110Zr and 126Pd should have7.5 x T1/2(FRDM)  350 ms → 2 x T1/2(130Cd) at top of r-peak • it must be the progenitor masses, via Sn (and correlated deformation ε2)

  22. b-decay freeze-out Nuclear-data needs for the classical r-process • b-decay properties T1/2r-process progenitor abundances, Nr,prog Pn  smoothing Nr,prog Nr,final (Nr,) modulation Nr through re-capture • nuclear masses Sn-values  r-process path / “boulevard” Qb, Sn-values  theoretical b-decay properties, n-capture rates • neutron capture rates sRC + sDC  smoothing Nr,prog during freeze-out in “non-equilibrium” phase(s) • fission modes SF, bdf, n- and n-induced fission  “fission (re-) cycling”; r-chronometers • nuclear structure development • level systematics • “understanding” b-decay properties • - short-range extrapolation into unknown regions

  23. Effects of T1/2 on r-process matter flow T1/2x 3 T1/2: 3 T1/2 (GT + ff) • Mass model: ETFSI-Q • all astro parameters (T9, nn, τn) • kept constant • r-Process model: • “waiting-point approximation“ r-matter flow too slow r-matter flow too fast

  24. 132Sn 50 (n,) 134 135 136 137 133 131 165ms Pn~85% 278ms (n,) 134 135 132 130 162ms 131 132 133 129 46ms(g) 158ms(m) 130 128 133In84 49 131In82 49 127 130Cd82 48 r-process path 129Ag82 126 47 (n,) 128Pd82 46 127Rh82 45 130Cd – the key isotope at the A=130 peak …hunting for nuclear properties of waiting-point isotope 130Cd… already B²FH (Revs. Mod. Phys. 29; 1957) C.D. Coryell (J. Chem. Educ. 38; 1961) b “climb up thestaircase“ at N=82; major waiting point nuclei; “break-through pair“ 131In, 133In; K.-L. Kratz (Rev. Mod. Astr. 1; 1988) climb up the N= 82 ladder ... A  130 “bottle neck“ “association with the rising side of major peaks in the abundance curve“ ? T1/2(130Cd) Nr,ʘ(130Te)

  25. "Waiting-point" estimate T1/2(130Cd) If the historical "waiting-point" concept is valid for the A ≈ 130Nr,ʘ-peak, then in the simplest version with Sn(N=82)=const. From this assumption, in 1986 the waiting-point prediction for T½(130Cd) ≈ 595 ms. With a more realistic approach, taking into account that • the breakout from N=82 involves 131In und 133In (≈ 1:1) • 133In has a known Pn ≈ 90% …to be compared to the 1986 exp. value of 195 (35) ms, and to the 2001 improved value of 162 (7) ms.

  26. Nuclear models to calculate T1/2 106 103 1 Theoretically, the gross β-decay quantities, T1/2 and Pn, are interrelated via the so-called β-strength function [Sb(E)] “Theoretical” definition (Yamada & Takahashi, 1972) “Experimental” definition (Duke et al., 1970) b(E) Sb(E) = D-1 · M(E) ² · (E) [s-1MeV-1] [s-1MeV-1] Sb(E) = f(Z, Qb-E) · T1/2 b(E) absolute b-feeding per MeV, f(Z, Qb-E) Fermi function, T1/2 b-decay half-life. M(E)  average b-transition matrix element (E) level density D const., determines Fermi coupling constant gv² 1 T1/2 as reciprocal ft-value per MeV T1/2 = Sb(Ei) x f (Z,Qb-Ei) 0Ei Qb Sb(E) 6x105 Fermi function f(Z, Qb-Ei)  (Qb-Ei)5 3x103 T1/2 sensitive to lowest-lying resonances in Sb(Ei) Pn sensitive to resonances in Sb(Ei) just beyond Sn Qb same T1/2 ! 1 ↷ easily “correct” T1/2 with wrong Sb(E) 11 E*[MeV] 1 5 10

  27. T1/2 and Pn calculations in 3 steps – (I) “Typical spherical example”: • Mass model FRDM • ↷ Qb, Sn, e2 • Folded-Yukawa wave fcts. • SP shell model QRPA (pure GT) • with input from FRDM • potential: Folded Yukawa • pairing-model: Lipkin-Nogami Sn Qb (2) as in (1) with empirical spreading of SP transition strength, as shown in experimental Sb(E) (3) as in (2) with addition of first-forbidden strength from Gross Theory note: effects on T1/2 and Pn !

  28. T1/2 and Pn calculations in 3 steps – (II) …and a typical“deformed”case: spreading of SP strength to deformed“Nilsson spaghetti” Möller, Nix & Kratz; ADNDT 66 (1997) Möller, Pfeiffer & Kratz; PRC 67 (2003) Note: low-lying GT-strength; ff-strength unimportant!

  29. Pn effects at the A≈130 peak • Significant differences • smoothing of odd-even Y(A) • staggering • (2) importance of individual • waiting-point nuclides, • e.g. 127Rh, 130Pd, 133Ag, 136Cd • (3) shift left wing of peak

  30. Global T1/2 & Pn – calc. vs. exp. T1/2, Pn gross b-strength properties from theoretical models, e.g. QRPA in comparison with experiments. Requests: (I) prediction / reproduction of correct experimental “number” (II) full nuclear-structure understanding ↷full spectroscopy of “key” isotopes, like 80Zn50 , 130Cd82. Total Error = 3.73 Total Error = 5.54 Pn-values Half-lives QRPA (GT) QRPA (GT) QRPA (GT+ff) QRPA (GT+ff) (Möller, Pfeiffer, Kratz PR C67, 055802 (2003)) Total Error = 3.52 Total Error = 3.08

  31. b-decay freeze-out Nuclear-data needs for the classical r-process • b-decay properties T1/2r-process progenitor abundances, Nr,prog Pn  smoothing Nr,prog Nr,final (Nr,) modulation Nr through re-capture • nuclear masses Sn-values  r-process path / “boulevard” Qb, Sn-values  theoretical b-decay properties, n-capture rates • neutron capture rates sRC + sDC  smoothing Nr,prog during freeze-out in “non-equilibrium” phase(s) • fission modes SF, bdf, n- and n-induced fission  “fission (re-) cycling”; r-chronometers • nuclear structure development • level systematics • “understanding” b-decay properties • - short-range extrapolation into unknown regions

  32. E(2+) - landscape 90  A  150 Z • reduced pairing • rigid rotors • g7/2  g9/2 interaction • shell quenching E(2+) 90Zr 132Sn 96Zr 50 d5/2 56 110Zr 60 s1/2 g7/2 r-process path h11/2 • magic shells/subshells • shape transitions/coexistence • intruder states • identical bands d3/2 50 82 g9/2 40 N

  33. What is known experimentally ? Known 1+ states in n-rich even-A In isotopes OXBASH (B.A. Brown, Oct. 2003) 1+ 2181 1+ 2120 (new) 1+ 1382 1+ 1173 (old) 1731 keV Reduction of the TBME (1+) by 800 keV 1+ 688 1+ 243 3+ 473 3+ 0 3+ 0 3+ 0 3+ 389 124In75 126In77 128In79 1- 0 1- 0 130In81 130In81 Dillmann et al.; PRL 91 (2003) Configuration 1- : nh11/2 pg9/2 Configuration 3+ : nd3/2 pg9/2 Configuration 1+ : ng7/2 pg9/2 determines T1/2

  34. Short range extrapolation Beta-decay odd-mass, N=82 isotones nSP states in N=81 isotones extrapolation Known ! partly known E*[MeV] S1n=3.98MeV S1n=5.246MeV S1n=3.59MeV S1n=2.84MeV 2648 2643 ng7/2 7/2+ 7/2+ 2637 67% 4.1 45% 4.25 24% 4.5 2607 7/2+ 88% 4.0 ng7/2 2565 89% 4.0 P1n=25% P2n=45% P3n=11% P1n=39% P2n=11% P3n= 4.5% P1n=29% P2n= 2% S1n=1.81MeV Pn=4.4% Pn=9.3% P4n= 8.5% P5n= 1% T1/2 determined by Qb-E7/2 908 1/2+ 814 1/2+ 1/2+ 728 601 1/2+ 536 ns1/2 524 3/2+ 472 3/2+ 414 3/2+ 331 3/2+ 282 nd3/2 Ib log(ft) nh11/2 11/2- 11/2- 11/2- 11/2- 1.2% 6.3 0.6% 6.4 2.3% 6.3 0.9% 6.4 0.5% 6.45 0 123Mo81 125Ru81 131Sn81 127Pd81 129Cd81 42 44 46 50 48

  35. Surprising b-decay properties of 131Cd …just ONE neutron outside N=82 magic shell Experiment: T1/2 = 68 ms; Pn = 3.4 % QRPA predictions: T1/2(GT) = 943 ms; Pn(GT)= 99 % T1/2(GT+ff) = 59 ms; Pn(GT+ff)= 14 % nuclear-structure requests: higher Qβ, main GT lower, low-lying ff-strength; later, g-spectroscopic confirmation of decay scheme at ISOLDE

  36. The FK2L waiting-point approach (I) e.g.: Cameron, Clayton, Schramm, Truran, Kodama, Arnould, Woosley, Hillebrandt, Thielemann… 30 known r-process isotopes at that time: N=5079Cu, 80Zn, 81Ga N=82130Cd, 131In

  37. The FK2L waiting-point approach (II) Classical assumptions: global steady flow of r-process through N=5080Zn, N=82130Cd and N=126195Tm r-process matter flow at freeze-out temperature ; Calculation: at N=82 “imperfect” peak, r-process through 40 s 132Sn, instead of 195 ms 130Cd…

  38. The FK2L waiting-point approach (III)

  39. The FK2L waiting-point approach (IV) “…best fit so far…; long-standing problem solved…” W. Hillebrandt “…call for a deeper study… before rushing into numerical results… and premature comparisons with the observed abundances” M. Arnould birth of N=82 “shell-quenching” idea …

  40. Wide-spread ignorance of experimental r-process data • Two typical examples: • I. Dillmann & Y.A. Litvinov • Prog. Part. Nucl. Phys. 66 (2011) • “Up to now, one could only“scratch”the regions where the r-process takes place.” • M.R. Mumpower, G.C. McLaughlin & R. Surman • Ap.J. 752 (2012) • “…current experimental data on neutron-rich isotopes is sparse.” But …”recent developments using radioactive beams show promise[ Hosmer et al. (2005) 78Ni; Jones et al. (2009) 132Sn ].”

  41. History and progress in measuring r-process nuclei Already26 years ago, in 1986 a new r-process astrophysics era started: • at the ISOL facilities OSIRISand TRISTAN T1/2 ofN=50“waiting-point” isotope540 ms80Zn (top of A ≈ 80 Nr, peak) • at the ISOL facility SC-ISOLDE T1/2 ofN=82“waiting-point” isotope195 ms130Cd (top of A ≈130 Nr, peak) Both act as major “bottle-necks” for the matter flow of the classical r-process starting from an Fe-group seed

  42. Z N Experimental information on r-process nuclides Today, altogether ≈ 80 r-process nuclei known 82 84 86 88 90 92 94 Ba Cs heaviest isotopes with measured T1/2 Xe I new (MSU, 2009; RIKEN 2011) Te Sb Sn In Cd Ag g9/2 Pd Rh Ru Tc Mo Nb Zr p1/2 Y Sr Rb p3/2 Kr Br Se As f5/2 Ge Ga Zn Cu Ni f7/2 Co Fe 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 8082 h11/2 d3/2 g9/2 d5/2 g7/2 s1/2

  43. nn=1020 Z N Classical r-process path for nn=1020 82 84 86 88 90 92 94 Ba Cs Xe I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr Rb Kr Br Se As Ge Ga Zn Cu Ni Co Fe 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 8082 „waiting-point“ isotopes at nn=1020 freeze-out

  44. nn=1020 nn=1023 Z N Classical r-process paths for nn=1020 and 1023 82 84 86 88 90 92 94 Ba Cs Xe I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr Rb Kr Br Se As Ge Ga Zn Cu Ni Co Fe 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 8082 „waiting-point“ isotopes at nn=1023 freeze-out (T1/2 exp. : 28Ni – 31Ga, 36Kr – 40Zr, 47Ag – 51Sb)

  45. nn=1020 nn=1023 nn=1026 Z N r-Process paths for nn= 1020, 1023 and 1026 r-process “boulevard” 82 84 86 88 90 92 94 Ba Cs Xe I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr Rb Kr Br Se As Ge Ga Zn Cu Ni Co Fe 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 8082 „waiting-point“ isotopes at nn= 1026 freeze-out (T1/2 exp. : 28Ni, 29Cu, 47Ag – 50Sn)

  46. Summary “waiting-point” model seed Fe (still implies secondary process) superposition of nn-components …largely site-independent! T9 and nn constant; instantaneous freezeout “weak” r-process (later secondary process; explosive shell burning?) “main” r-process (early primary process; SN-II?) Kratz et al., Ap.J. 662 (2007)

More Related