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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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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
X-rays in the sky D.A. Smith, M. Muno, A.M. Levine, R. Remillard, H. Bradt 2002(RXTE All Sky Monitor)
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
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
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)
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
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)
H. Schatz Observation of thermonuclear energy Unstable, explosive burning in bursts (release over short time) Burst energythermonuclear Persistent fluxgravitational energy
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 !
H. Schatz At large (local) accretion rates at high localaccretion rates m > medd (medd generates luminosity Ledd) Triple alpha reaction rate Stable nuclear burning
H. Schatz X-ray pulsar > 1012 Gauss ! High local accretion rates due to magnetic funneling of material on small surface area
Golden Age for X-ray Astronomy ? XMM Newton Constellation X RXTE XMM Chandra RXTE
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 ?
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 ?)
H. Schatz Open question II: ignition and flame propagation Anatoly Spitkovsky (Berkeley)
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
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
H. Schatz EXO0748-676 Cottam, Paerels, Mendez 2002 Open question V: abundance observations ?
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
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
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
Step 1: Thermonuclear burning in atmosphere Neutron star surface H,He X-ray burst gas ~ 4m, r=106 g/cm3 ocean outer crust Innercrust
Woosley et al. 2003 Kippenhahndiagram depth time
H. Schatz Ignition layer ocean Burst cooling J. Fisker Thesis (Basel, 2004) Ignition surface Conditions during an X-ray burst
H. Schatz Visualizing reaction networks Protonnumber (a,g) (p,g) (a,p) 14 27Si (,b+) 13 neutron number Lines = Flow =
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
H. Schatz How the rp-process works • Nuclear lifetimes: (average time between a …) • A+pB+gproton capture : t = 1/(Ypr NA <sv>) • b+ decay : t = T1/2/ln2 • B+gA+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 ?
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
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
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)