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The rapid proton capture process(rp-process)
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Nova Cygni 1992with HST
Sites of the rp-process
KS 1731-260with Chandra
E0102-73.3composite
Novae-wind insupernovae ? X-ray binaries
• “r”p-process (not really a full rp-process)
• makes maybe 26Al
•makes maybe 45Sc and 49Ti
• if n accelerated( interactions)maybe a majornucleosynthesisprocess?
• full rp-process
• unlikely to contribute to nucleosynthesis
This lecture
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D.A. Smith, M. Muno, A.M. Levine,R. Remillard, H. Bradt 2002(RXTE All Sky Monitor)
X-rays in the sky
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0.5-5 keV (T=E/k=6-60 x 106 K)
Cosmic X-rays: discovered end of 1960’s:
Nobel Price in Physics 2002for Riccardo Giacconi
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Discovery
First X-ray pulsar: Cen X-3 (Giacconi et al. 1971) with UHURU
First X-ray burst: 3U 1820-30 (Grindlay et al. 1976) with ANS
Today:~50
Today:~70 burst sources out of 160 LMXB’s
Total ~230 X-ray binaries knownTotal ~230 X-ray binaries known
T~ 5s
10 s
H. Schatz
Discovery of X-ray bursts and pulsars
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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
Burst characteristics
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Accreting neutron stars
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Accreting neutron stars
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Neutron Star
Donor Star(“normal” 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
The model
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NASA
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Energy generation: thermonuclear energy
Ratio gravitation/thermonuclear ~ 30 – 40(called )
4H 4He
5 4He + 84 H 104Pd
6.7 MeV/u
0.6 MeV/u
6.9 MeV/u
Energy generation: gravitational energy
E = G M mu
R= 200 MeV/u
3 4He 12C (“triple alpha”)
(rp process)
H. Schatz
Energy sources
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Unstable, explosive burning in bursts (release over short time)
Burst energythermonuclear
Persistent fluxgravitational energy
H. Schatz
Observation of thermonuclear energy
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0 1 10te m p e ra ture (G K)
10-15
10-14
10-13
10-12
10-11
10-10
10-9
rea
ctio
n ra
te (c
m2 s-1
mo
le-1
)
Burst trigger rate is “triple alpha reaction” 3 4He 12C
Ignition: dnuc
dTdcool
dT>
nuc
cool ~ T4
Ignition < 0.4 GK: unstable runaway (increase in T increases nuc that increases T …)
degenerate e-gas helps !
Triple alpha reaction rate
BUT: energy release dominated by subsequent reactions !
Nuclear energy generation rate
Cooling rate
H. Schatz
Burst ignition
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10-2
10-1
100
accretion rate (L_edd)
0.16
0.17
0.18
0.19
0.2
0.21
0.22
0.23
0.24
tem
pera
ture
(G
K)
0 1 10te m p e ra ture (G K)
10-15
10-14
10-13
10-12
10-11
10-10
10-9
rea
ctio
n ra
te (c
m2 s-1
mo
le-1
)
Triple alpha reaction rate
at high localaccretion rates m > medd
(medd generates luminosity Ledd)
Stable nuclear burning
H. Schatz
At large (local) accretion rates
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> 1012 Gauss !
High local accretion rates due to magnetic funneling of material on small surface area
H. Schatz
X-ray pulsar
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http://www.gsfc.nasa.gov/topstory/2003/0702pulsarspeed.html
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RXTEXMM
Chandra
XMM Newton
RXTE
Constellation X
Golden Age for X-ray Astronomy ?
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4U1728-34Rossi X-ray Timing ExplorerPicture: T. Strohmeyer, GSFC
Neutron Star spin frequency
• Origin of oscillations ?• Why frequency drift ?
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)
H. Schatz
Open question I: ms oscillations
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Seconds since burst
D. Chakrabarty et al. Nature 424 (2003) 42
SAX J1808.4-3658
PulsarFrequency
H. Schatz
The bursting pulsar
Origin of frequency drift in normal bursting systems ???(rotational decoupling ? Surface pulsation modes ?)
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Anatoly Spitkovsky (Berkeley)
H. Schatz
Open question II: ignition and flame propagation
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Regular burst rate /day
Accretion rate (Edd units)
Cornelisse et al. 2003
superbursts
Regular burst duration (s)
500-5000
superbursts
Accretion rate (Edd units)
H. Schatz
Open question III: burst behavior at large accretion rates
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4U 1820-30
Normal Burst
X 1000 duration ( can last ½ day)
X 1000 energy
11 seen in 9 sources
Recurrence ~1 yr ?
Often preceeded by regular burst
H. Schatz
Open question IV: superbursts
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Cottam, Paerels, Mendez 2002
EXO0748-676
H. Schatz
Open question V: abundance observations ?
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Galloway et al. 2003
97-98
2000
Precision X-ray observations(NASA’s RXTE)
Woosley et al. 2003 astro/ph 0307425
But only with precision nuclear physics
Uncertain models due to nuclear physics
Burst models withdifferent nuclear physicsassumptions
Burst models withdifferent nuclear physicsassumptions
GS 1826-24 burst shape changes ! (Galloway 2003 astro/ph 0308122)
H. Schatz
New era of precision astrophysics
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Neutron star surface
Neutron star surfaceAccreted matter (ashes)
Neutron star surface
Neutron star surface
Neutron star surface
Neutron star surface
Fate of matter accreted onto a neutron star
accretion rate: ~10 kg/s/cm2
Accreted matter is incorporated deeper into the neutron star
As the density increases interesting things happen
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Accreting Neutron Star Surface
fuel
ashesocean
Innercrust
outercrust
H,He
gas
core
’sX-ray’s
~1 m
~10 m
~100 m
~1 km
10 km
Thermonuclear H+He burning(rp process) X-ray bursts
Deep burning ? superbursts
Crust processes(EC, pycnonuclear fusion)crust heatingcrust conductivity
Spallation of heavy nuclei ?
H. Schatz
Nuclear physics overview
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Neutron star surface
ocean
Innercrust
outercrust
H,He
gas
Step 1: Thermonuclear burning in atmosphere
~ 4m, =106 g/cm3
X-ray burst
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depth
time
Kippenhahndiagram
Woosley et al. 2003
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Ignition layer
surface
ocean
Ignition
Burst cooling
J. FiskerThesis(Basel, 2004)
H. Schatz
Conditions during an X-ray burst
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27Si
neutron number13
Protonnumber
14
(p,) (,p)
(,)
(,)
Lines = Flow = dtdt
dY
dt
dYF
ij
j
ji
iji
,
H. Schatz
Visualizing reaction networks
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0 1
2
3 4 5
6
7
8
9 10
11 12
13 14
15 16
17 18 19 20
21 22
23 24
25 26 27 28
29 30
31 32
33 34 35 36
37 38 39 40
41 42 43 44
45 46
47 48 49 50
51 52 53 54
n (0)
H (1)
H e (2)
L i (3)
Be (4)
B (5 )
C (6)
N (7)
O (8)
F (9 )
N e (10)
N a (11)
M g (12)
A l (13)
S i (14)
P (15)
S (16)
C l (17)
A r (18)
K (19)
C a (20)
Sc (21)
Ti (22)
V (23)
C r (24)
M n (25)
Fe (26)
C o (27)
N i (28)
C u (29)
Zn (30)
G a (31)
G e (32)
As (33)
Se (34)
B r (35)
K r (36)
R b (37)
S r (38)
Y (39)
Zr (40)
N b (41)
M o (42)
Tc (43)
R u (44)
R h (45)
Pd (46)
Ag (47)
C d (48)
In (49)
Sn (50)
Burst Ignition:
Prior to ignition : hot CNO cycle~0.20 GK Ignition : 3
: Hot CNO cycle II
~ 0.68 GK breakout 1: 15O()
~0.77 GK breakout 2: 18Ne(,p)
(~50 ms after breakout 1)Leads to rp process and main energy production
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38 39 40 41 42 43neutron num ber
10-10
10-8
10-6
10-4
10-2
100
102
104
106
108
1010
Life
time
(s)
N=41
38 (Sr)
39 (Y)
40 (Zr)
41 (Nb)
42 (Mo)
43 (Tc)
Z
Proton number
Nuclear lifetimes: (average time between a …)• A+pB+ proton capture : = 1/(Yp NA <v>)• decay : = T1/2/ln2• B+A+p photodisintegration : = 1/p
(for =106 g/cm3, Yp=0.7, T=1.5 GK)
H. Schatz
How the rp-process works
Endpoint ?
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Possibilities: • Cycling (reactions that go back to lighter nuclei)• Coulomb barrier• Runs out of fuel• Fast cooling
Possibilities: • Cycling (reactions that go back to lighter nuclei)• Coulomb barrier• Runs out of fuel• Fast cooling
0 10 20 30 40 50 60 70 80charge num ber Z
10-10
10-8
10-6
10-4
10-2
100
102
104
lifet
ime
(s)
Proton capture lifetime of nuclei near the drip line
Eventtimescale
H. Schatz
The endpoint of the rp-process
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Slow reactions extend energy generation abundance accumulation (steady flow approximation Y=const or Y ~ 1/)
Critical “wating points” can be easily identified in abundance movie
H. Schatz
Waiting points
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0 1 2
3 45 6
7 8
9 10
11 12 13
14
15 16
17 18 19 20
21 22
23 24
25 26 27 28
29 30
31 32
33 34 35 36
37 38 39 4041
42 43 44
45 46 47 48
49 5051 52
5354 55
56
57 58
59
H (1)H e (2)L i (3)
Be (4) B (5) C (6) N (7)
O (8) F (9)
N e (10)N a (11)
M g (12)A l (13)S i (14) P (15)
S (16)C l (17)
A r (18) K (19)
C a (20)Sc (21)
Ti (22) V (23)
C r (24)M n (25)
Fe (26)C o (27)
N i (28)C u (29)
Zn (30)G a (31)
G e (32)As (33)
Se (34)B r (35)K r (36)R b (37)
S r (38) Y (39)
Zr (40)N b (41)
M o (42)Tc (43)
R u (44)R h (45)Pd (46)Ag (47)
C d (48)In (49)
Sn (50)Sb (51)
Te (52) I (53)
Xe (54)
The Sn-Sb-Te cycle
1 0 4S b 1 0 5S b 1 0 6 1 0 7S b
1 0 3S n 1 0 4S n 1 0 5S n 1 0 6S n
1 0 5Te 1 0 6Te 1 0 7Te 1 0 8Te
1 0 2In 1 0 3In 1 0 4In 1 0 5In
(,a )
S b
(p , )
Known ground state emitter
Endpoint: Limiting factor I – SnSbTe Cycle
Collaborators:L. Bildsten (UCSB)A. Cumming (UCSC)M. Ouellette (MSU)T. Rauscher (Basel)F.-K. Thielemann (Basel)M. Wiescher (Notre Dame)
(Schatz et al. PRL 86(2001)3471)