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In detail: ap process Ga (31) Zn (30) Cu (29) Ni (28) 333 Co (27) Fe (26) 3132 Mn (25) Cr (24) 2930 V (23) Ti (22) 25262728 Sc (21) Ca (20) 2324 K (19) Ar (18) 2122 Cl (17) S (16) 17181920 P (15) Si (14) 12C a+a+a 1516 Al (13) Mg (12) 14O+a 17F+p 14 Na (11) 17F+p 18Ne Ne (10) 18Ne+a … 11 1213 F (9) O (8) 9 10 N (7) Alternating (a,p) and (p,g) reactions: C (6) For each proton capture there is an 7 8 B (5) Be (4) (a,p) reaction releasing a proton Li (3) 5 6 He (2) Net effect: pure He burning 3 4 H (1) 0 1 2 3a reaction ap process: Mass known < 10 keV Recent progress in mass measurements Mass known > 10 keV Only half-life known seen Measure: decay properties gs masses level properties rates/cross sections ISOLTRAP Rodriguez et al. NSCL Lebit Bollen et al. ANL CPT Savard et al. JYFL Trap NSCL Set of experiments use (p,dg) to determine level structure Reaction rates: • direct measurements difficult • “indirect” methods: • Coulomb breakup • (p,p) • transfer reactions stable beams and RIBS Figure: Schatz&Rehm, Nucl. Phys. A, Guide direct measurements Huge reduction in uncertainties If capture on excited states matters only choice Nuclear physics needed for rp-process: • b-decay half-lives (ok) (in progress) • masses (just begun) • reaction rates Xe (54) I (53) Te (52) Sb (51) Sn (50) In (49) Cd (48) Ag (47) Pd (46) Rh (45) Ru (44) 5758 Tc (43) Mo (42) Nb (41) Zr (40) Y (39) Sr (38) mainly (p,g), (a,p) 56 5455 Rb (37) Kr (36) Br (35) Se (34) 53 5152 4950 As (33) Ge (32) Ga (31) Zn (30) 45464748 424344 41 Cu (29) 37383940 Ni (28) Co (27) 33343536 Fe (26) Mn (25) 3132 Cr (24) V (23) 2930 Ti (22) Sc (21) 25262728 Ca (20) K (19) 2324 Ar (18) Cl (17) 2122 S (16) P (15) 17181920 Si (14) Al (13) 1516 Mg (12) Na (11) 14 Ne (10) F (9) 11 1213 O (8) N (7) 9 10 C (6) B (5) 7 8 Be (4) some experimental information available (most rates are still uncertain) Theoretical reaction rate predictions difficult near drip line as single resonances dominate rate: Hauser-Feshbach: not applicable Shell model: available up to A~63 but large uncertainties (often x1000 - x10000) Li (3) He (2) 5 6 H (1) 3 4 n (0) 2 0 1 (Herndl et al. 1995, Fisker et al. 2001) Need rare isotope beam experiments H. Schatz Techniques with rare isotope beams 21Na 1) Direct Measurements + p 22Mg Bishop et al. 2003 (TRIUMF) For p-capture only 2 cases so far ! Need RIA 2) First step: indirect techniques with low intensity rare isotope beams Many developed at a number of facilities: (ANL, GSI, MSU, ORNL, RIKEN, Texas A&M, …) Example: 32Cl + p 33Ar* 33Ar + g Resonant enhancement through states in 33Ar ? H. Schatz NSCL Experiment: Clement et al. PRL 92 (2004) 2502 Doppler corrected g-rays in coincidence with 33Ar in S800 focal plane: 34Ar g-rays from predicted 3.97 MeV state 33Ar excited Plastic d 33Ar level energies measured: 3819(4) keV (150 keV below SM) 3456(6) keV (104 keV below SM) reaction rate (cm3/s/mole) stellar reaction rate with shellexperimental model only data x 3 uncertainty x10000 uncertainty temperature (GK) H. Schatz Stellar Enhancement Factor SEF = 1/2+ Dominant resonance 5/2+ MeV 4.190 3.819 this work 7/2+ 2+ 90 keV stellar capture rate ground state capture rate 5/2+ 1+ 32Cl 3.456 3.364 3.343 NON Smoker 33Ar direct measurement of this rate is not possible – need indirect methods SEF’s should be calculated with shell model if possible H. Schatz Mass ejection in X-ray bursts ? Weinberg, Bildsten, Schatz 2005 Winds can eject <1% of accreted mass Does convection zone reach into the outer layers that get blown off ??? Wind ejects ashes in radius expansion bursts for wide range of parameters Neutron star interior Temperature (K) wind ? surface Column density (g/cm2) wind H. Schatz Reaction flow during burst rise in pure He flash 12C(a,g) bypass (a,p) 13N 16O slow (p,g) 12C Need protons as catalysts (~10-9 are enough !) Source: (a,p) reactions and feedback through bypass Increases risetime Triggers late reexpansion of convection zone enhances production of heavy elements vs. carbon H. Schatz Composition of ejected material 28Si 32S Weak p-capture on initial Fe seed Observable with current X-ray telescopes in wind on NS surface as spectral edges Explanation for enhanced Ne/O ratio in 4U1543-624, 4U1850-087, … ??? (ratios ~1 – ISM 0.18) H. Schatz Step 2: Deep ocean burning: Superbursts Neutron star surface H,He gas ashes ocean outer crust Inner crust ~ 20m, r=109 g/cm3 H. Schatz The origin of superbursts – Ashes to Ashes Accreting Neutron Star Surface Radiation transport H,He ~10s ~hours ~1 m fuel ~ x1000 longer burst duration ~ x1000 longer recurrence time ~ x1000 more energy Thermonuclear H+He burning (rp process) gas ashes ~10 m ocean ~100 m outer crust ~1 km 10 km Inner crust core Deep burning ? long duration through longer radiation transport long time to accumulate means long recurrence time more material means more total energy by same factor for same MeV/u) Ashes to ashes – the origin of superbursts ? 54 52 50 48 68 44 42 62 40 (Cumming & Bildsten 2001) 38 36 54 34 30 44 28 34 20 14 20 22 16 18 8 14 6 10 12 4 0 2 4 6 48 ~ 55% Energy 44 48 24 26 28 8 42 62 38 36 54 34 36 30 44 28 30 24 38 Time: 1.041e-04 s 20 Temperature: 180.850 GK 20 22 10 16 18 8 14 6 10 12 4 0 0 2 4 6 34 8 (Schatz, Bildsten, Cumming, ApJ Lett. 583(2003)L87 46 48 24 40 36 32 16 12 60 42 26 ~ 45% Energy 14 56 58 64 66 50 52 32 2 68 40 22 10 0 46 32 18 2 60 46 40 38 22 16 52 50 42 26 12 56 58 54 64 66 50 52 32 24 Burst peak (~7 70 46 Carbon can explode deep in ocean 30 Puzzle: The ocean is too cold s Time: 1.076e+03 Temperature: ignition about every 6.607 GK10 years instead of every year as observed 26 28 Energy generation in Superbursts (plus C->Ni fusion) And nuclear power plants only place in cosmos ? on earth Energy generation everywhere else in comos: • Stars • X-ray bursts, Novae H. Schatz Step 3: Crust burning Neutron star surface H,He gas ashes ocean outer crust Inner crust ashes ~ 25 – 70 m r=109-13 g/cm3 Surface of accreting neutron stars Neutron star surface Hydrogen, Helium X-ray bursts 1m gas 10m Ocean (palladium? Zinc?) Crust of rare isotopes Inner crust D. Page ashes Crust processes 106Pd Known mass 4.8 x 1011 g/cm3 106Ge 56Fe 1.8 x 1012 g/cm3 68Ca 2.5 x 1011 g/cm3 56Ar 72Ca 4.4 x 1012 g/cm3 1.5 x 1012 g/cm3 34Ne Haensel & Zdunik 1990, 2003 Gupta et al. 2006 Crust processes Recent mass measurements at GSI (Scheidenberger et al., Matos et al.) Recent mass measurements at Jyvaskyla (Hager et. al. 2006) Known mass Recent mass measurements at ISOLTRAP (Blaum et. al.) Q-value measurement at ORNL (Thomas et al. 2005) Recent TOF mass measurements at MSU (Matos et al.) Reach of next generation Rare Isotope Facility FRIB (here MSU’s ISF concept) (mass measurements) NEW JINA Result: S. Gupta, E. Brown, H. Schatz, K.-L. Kratz, P. Moeller 2007 Electron capture into excited states increases heating by up to a factor of ~10 Excitation energy of main transition Increased heating Enhanced crust heating New heating enhanced by x 5-6 Former estimate Heats entire crust and increases ocean temperature from 480 Mio K to 500 Mio K Impact of new crust modeling on superbursts Can the additional heating from EC into excited states make the crust hot enough to get the superburst ignition depth in line with observations ? Almost: Ignition depth Without excited states Inferred from observations Mass number of crust composition (pure single species crust) H. Schatz Observables: transients in quiescence Low crust conductivity, normal core cooling KS 1731-260 (Wijands 2001) Bright X-ray burster for ~12 yr Accretion shut off early 2001 Is residual luminosity cooling neutron star crust ? If yes: probe neutron star ! (Ouellette & Brown 2005) (Rutledge 2002) High crust conductivity, enhanced core coolin H. Schatz Comparison with observations during quiescence M. Ouellette Low crust conductivity Normal core cooling High crust conductivity Normal core cooling Low crust conductivity Enhanced core cooling High crust conductivity Enhanced core cooling (data from Wijnands 2004) but: a superburst has been observed from KS 1731-260 this indicates a hotter crust and low crust conductivity (Brown 2004) H. Schatz Superbursts as probes for NS cooling Superburst ignition depth (Ed Brown, to be published) (for accretion rate of 3e17 g/s and X(12C)=0.1) Low crust conductivity High crust conductivity Recurrence times (observed ~ 1yr) 1.4 yr 3.1 yr 5.2 yr “regular” core cooling 27 yr “enhanced” core cooling Recurrence time depends on crust conductivity and core cooling Observations require LOW conductivity and no enhanced cooling (incl. KS1731-260)