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The rapid proton capture process (rp-process)

The rapid proton capture process (rp-process). Nova Cygni 1992 with HST. This lecture. KS 1731-260 with Chandra. E0102-73.3 composite. Sites of the rp-process. n -wind in supernovae ?. Novae. X-ray binaries. “ r”p-process (not really a full rp-process) makes maybe 26 Al.

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The rapid proton capture process (rp-process)

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  1. The rapid proton capture process(rp-process)

  2. Nova Cygni 1992with HST This lecture KS 1731-260with Chandra E0102-73.3composite Sites of the rp-process n-wind insupernovae ? Novae X-ray binaries • “r”p-process (not really a full rp-process) • makes maybe26Al • makes maybe45Sc and 49Ti • if n accelerated(n interactions)maybe a major • nucleosynthesis • process? • full rp-process • unlikely to contribute to nucleosynthesis

  3. X-rays in the sky D.A. Smith, M. Muno, A.M. Levine, R. Remillard, H. Bradt 2002(RXTE All Sky Monitor)

  4. Cosmic X-rays: discovered end of 1960’s: 0.5-5 keV (T=E/k=6-60 x 106 K) Nobel Price in Physics 2002for Riccardo Giacconi

  5. H. Schatz Discovery Discovery of X-ray bursts and pulsars First X-ray pulsar: Cen X-3 (Giacconi et al. 1971) with UHURU T~ 5s Today:~50 First X-ray burst: 3U 1820-30 (Grindlay et al. 1976) with ANS 10 s Today:~70 burst sources out of 160 LMXB’s Total ~230 X-ray binaries known

  6. H. Schatz Burst characteristics • Typical X-ray bursts: • 1036-1038 erg/s • duration 10 s – 100s • recurrence: hours-days • regular or irregular Frequent and very brightphenomenon ! (stars 1033-1035 erg/s)

  7. Accreting neutron stars

  8. Accreting neutron stars

  9. H. Schatz The Model Donor Star(“normal” star) Neutron Star Accretion Disk The model Neutron stars:1.4 Mo, 10 km radius(average density: ~ 1014 g/cm3) • Typical systems: • accretion rate 10-8/10-10 Mo/yr (0.5-50 kg/s/cm2) • orbital periods 0.01-100 days • orbital separations 0.001-1 AU’s

  10. NASA

  11. H. Schatz 3 4He 12C G M mu = 200 MeV/u E = R Energy sources Energy generation: thermonuclear energy 6.7 MeV/u 4H 4He (“triple alpha”) 0.6 MeV/u (rp process) 6.9 MeV/u 5 4He + 84 H 104Pd Energy generation: gravitational energy Ratio gravitation/thermonuclear ~ 30 – 40(called a)

  12. H. Schatz Observation of thermonuclear energy Unstable, explosive burning in bursts (release over short time) Burst energythermonuclear Persistent fluxgravitational energy

  13. H. Schatz 3 4He 12C Burst ignition Burst trigger rate is “triple alpha reaction” enuc denuc decool Nuclear energy generation rate Ignition: > ecool ~ T4 dT dT Cooling rate Triple alpha reaction rate Ignition < 0.4 GK: unstable runaway (increase in T increasesenuc that increases T …) degenerate e-gas helps ! BUT: energy release dominated by subsequent reactions !

  14. H. Schatz At large (local) accretion rates at high localaccretion rates m > medd (medd generates luminosity Ledd) Triple alpha reaction rate Stable nuclear burning

  15. H. Schatz X-ray pulsar > 1012 Gauss ! High local accretion rates due to magnetic funneling of material on small surface area

  16. http://www.gsfc.nasa.gov/topstory/2003/0702pulsarspeed.html

  17. Golden Age for X-ray Astronomy ? XMM Newton Constellation X RXTE XMM Chandra RXTE

  18. H. Schatz Open question I: ms oscillations 4U1728-34 Rossi X-ray Timing Explorer Picture: T. Strohmeyer, GSFC Neutron Star spin frequency Now proof from 2 bursting pulsars (SAX J1808.4-3658, XTE J1814-338)(Chakrabarty et al. Nature 424 (2003) 42 Strohmayer et al. ApJ 596 (2003)67) • Origin of oscillations ? • Why frequency drift ?

  19. H. Schatz The bursting pulsar SAX J1808.4-3658 D. Chakrabarty et al. Nature 424 (2003) 42 PulsarFrequency Seconds since burst Origin of frequency drift in normal bursting systems ???(rotational decoupling ? Surface pulsation modes ?)

  20. H. Schatz Open question II: ignition and flame propagation Anatoly Spitkovsky (Berkeley)

  21. H. Schatz Regular burst duration (s) Regular burst rate /day a:~40 superbursts superbursts a: 500-5000 Accretion rate (Edd units) Accretion rate (Edd units) Cornelisse et al. 2003 Open question III: burst behavior at large accretion rates

  22. H. Schatz Open question IV: superbursts X 1000 duration ( can last ½ day) X 1000 energy 11 seen in 9 sources Recurrence ~1 yr ? Often preceeded by regular burst Superburst Normal Burst 4U 1820-30

  23. H. Schatz EXO0748-676 Cottam, Paerels, Mendez 2002 Open question V: abundance observations ?

  24. H. Schatz 97-98 2000 New era of precision astrophysics Uncertain models due to nuclear physics Precision X-ray observations(NASA’s RXTE) Galloway et al. 2003 Burst models withdifferent nuclear physicsassumptions  GS 1826-24 burst shape changes !(Galloway 2003 astro/ph 0308122) Woosley et al. 2003 astro/ph 0307425 But only with precision nuclear physics

  25. Neutron star surface Neutron star surface Neutron star surface Neutron star surface Neutron star surface Accreted matter (ashes) Fate of matter accreted onto a neutron star accretion rate: ~10 kg/s/cm2 Neutron star surface  Accreted matter is incorporated deeper into the neutron star  As the density increases interesting things happen

  26. H. Schatz Nuclear physics overview Accreting Neutron Star Surface H,He X-ray’s Spallation of heavy nuclei ? n’s fuel Thermonuclear H+He burning(rp process)  X-ray bursts ~1 m gas ashes Deep burning ? superbursts ocean ~10 m outer crust • Crust processes(EC, pycnonuclear fusion) • crust heating • crust conductivity ~100 m Innercrust ~1 km 10 km core

  27. Step 1: Thermonuclear burning in atmosphere Neutron star surface H,He X-ray burst gas ~ 4m, r=106 g/cm3 ocean outer crust Innercrust

  28. Woosley et al. 2003 Kippenhahndiagram depth time

  29. H. Schatz Ignition layer ocean Burst cooling J. Fisker Thesis (Basel, 2004) Ignition surface Conditions during an X-ray burst

  30. H. Schatz Visualizing reaction networks Protonnumber (a,g) (p,g) (a,p) 14 27Si (,b+) 13 neutron number Lines = Flow =

  31. Burst Ignition: Prior to ignition : hot CNO cycle ~0.20 GK Ignition : 3a : Hot CNO cycle II ~ 0.68 GK breakout 1: 15O(a,g) ~0.77 GK breakout 2: 18Ne(a,p) (~50 ms after breakout 1)Leads to rp process and main energy production

  32. H. Schatz How the rp-process works • Nuclear lifetimes: (average time between a …) • A+pB+gproton capture : t = 1/(Ypr NA <sv>) • b+ decay : t = T1/2/ln2 • B+gA+pphotodisintegration : t = 1/l(g,p) Z 43 (Tc) (for r=106 g/cm3, Yp=0.7, T=1.5 GK) 42 (Mo) 41 (Nb) 40 (Zr) 39 (Y) 38 (Sr) N=41 Proton number  Endpoint ?

  33. H. Schatz Proton capture lifetime of nuclei near the drip line Eventtimescale The endpoint of the rp-process • Possibilities: • Cycling (reactions that go back to lighter nuclei) • Coulomb barrier • Runs out of fuel • Fast cooling

  34. H. Schatz Waiting points Slow reactions  extend energy generation  abundance accumulation (steady flow approximation lY=const or Y ~ 1/l) Critical “wating points” can be easily identified in abundance movie

  35. Endpoint: Limiting factor I – SnSbTe Cycle The Sn-Sb-Te cycle Known ground statea emitter (Schatz et al. PRL 86(2001)3471) Collaborators: L. Bildsten (UCSB)A. Cumming (UCSC) M. Ouellette (MSU) T. Rauscher (Basel) F.-K. Thielemann (Basel) M. Wiescher (Notre Dame)

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