h. schatz michigan state university national superconducting cyclotron laboratory joint institute...
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H. Schatz Michigan State University
National Superconducting Cyclotron LaboratoryJoint Institute for Nuclear Astrophysics
The rp process in X-ray bursts astrophysics and experiments with fast radioactive beams
X-ray bursts
• Many new observations by Beppo-SAX, RXTE, Chandra, XMM-Newton lots of open questions
• Can learn about neutron stars• increase in mass, spin, temperature compared to isolated NS
• Bright and frequent (most common thermonuclear explosion in the universe)
Galloway et al. 2003
97-98
2000
Precision X-ray observations(NASA’s RXTE)
Woosley et al. 2003 astro/ph 0307425
Need much more precise nuclear data to make full use of high quality observational data
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)
Reality check: Burst comparison with observations
For example to determine XH distance, EOS
• Ejected composition (<few%) (Weinberg et al. 06 astro-ph/0511247 )
• Crust composition Crust heating (Gupta et al. astro-ph/0609828)
crust cooling superbursts
More observables – what about the produced nuclei ?
KS 1731-260
NASA/Chandra/Wijnands et al.
Likely no nucleosynthesis contributionGoal: understand systems and neutron stars
?
Mass known < 10 keV
Mass known > 10 keV
Only half-life known
seen
Figure: Schatz&Rehm, Nucl. Phys. A,
Reaction rates:• direct measurements difficult• “indirect” methods:
• Coulomb breakup• (p,p)• transfer reactions stable beams and RIBS
Guide direct measurements Huge reduction in uncertainties If capture on excited states matters only choice
NSCL Set of experimentsuse (p,d) to determinelevel structure
ISOLTRAPRodriguez et al.NSCL Lebit
Bollen et al.
ANL CPTSavard et al.
Recent progress in mass measurements
JYFL TrapKankainen et al.
SHIPTRAPMeasure: decay properties gs masses level properties rates/cross sections
Why measuring excitation energies ?
Coulombpenetrability
Boltzmann e-E/kT
+_100 KeV
Shellmodel(OXBASH)
32Cl(p,g)33Ar Reaction rate for T=0.4 x 109 KExample: contribution from one individual resonance (5/2+)
mole s
cmeMeV][)(1054.1
39T
MeV][rE605.11
2/39
11
ATvN A1
2 1
(2 1)(2 1)pr
T
J
J J
Focal plane:identify 33Ar
Plastic target34Ar (p,d) 33Ar
Radioactive 34Ar beam84 MeV/u T1/2=844 ms(from 150 MeV/u 36Ar)
33Ar
34Ar
Beamblocker
n-removal related to astrophysical 32Cl+p 33Ar+rate
-rays from predicted 3.97 MeV state
Doppler corrected -rays in coincidence with 33Ar in S800 focal plane:
SEGA
x 3 uncertainty(from x 1000)
New rates: Clement et al. PRL 92 (2004) 2502, Galaviz et al.
33Ar 33Ar
Sp 3343(8)
SM (Brown) Exp
3970 5/2+
104(6) keV150(4) keV
3560 7/2+
reac
tion
rate
(cm
3/s
/mol
e)
Clement et al.
Ex by
32Cl+p
Rate dominated by capture on low lying (90 keV) first excited state in 32Cl
Rate dominated by capture on low lying (90 keV) first excited state in 32Cl
32Cl(p,)33Ar
H. Schatz
Stellar Enhancement Factor
SEF = stellar capture rate
ground state capture rate
this work
NON Smoker
direct measurement of this rate is not possible – need indirect methods SEF’s should be calculated with shell model if possible
1+
2+90 keV
3.364
3.456
3.819
4.190
33Ar
32Cl
5/2+
7/2+
5/2+
1/2+MeV
3.343
Dominantresonance
Advantages of method:• reach as beam is less n-deficient (see chart) and thick targets can be used (fast beams, ’s)• measure isotones simultaneously• precise energies due to -detection
Limitations:- need -decay branch (d-spectroscopy being developed)- better for low level density (match with shell model/mirror, statistics limited for ) - has to be coordinated with precision mass measurements
Reach of method
Nuclei that can be studied at NSCL
Clement et al. PRL92,17502 (2004)Schatz et al. PRC72, 065804 (2005)
Program continued by D. GalavizM. AmthorA. Chen
HIRA experimentswith particle detection(Famiano, Lynch)
Summary
• Fast beams are important tool for rp-process reaction rate studies especially when reach to most exotic nuclei is required (p,d) in inverse kinematics is a useful method
a wide range of reactions is within reach at the NSCL
• Other tools are also needed low energy beams for direct rate measurements
New facility at MSU/NSCL is planned (gas stopping and reacceleration to astrophysical energies)
stable beams interdisciplinary environment Joint Institute for Nuclear Astrophysics (JINA) (www.jinaweb.org)
NSCL Reacceleration Stage Options
A1900/ Cyclotron Stopper/ Charge Breeder/ RFQ/ LINAC
Reaccelerated beam area
Stage I 1-2 MeV/u
Stage II 12 MeV/u
NSCL Layout with Stopping Station
At this stage, the lay-out of the low energy arena is for illustration only and requires significant user input (incl. user provided equipment)
x 3 uncertainty(from x 1000)
New rates: Clement et al. PRL 92 (2004) 2502, Galaviz et al.
33Ar 33Ar
Sp (3343)
SM (Brown) Exp
32Cl(p,)33Ar32Cl(p,)33Ar
3970 5/2+
104(6) keV150(4) keV
3560 7/2+
reac
tion
rate
(cm
3/s
/mol
e)
Clement et al.
Ex by
32Cl+p
29P+p
Other reactions in preparation Other reactions in preparation
30S 30S
4888 2+
4733 3+Sp (4399)
reac
tion
rate
(cm
3/s
/mol
e)
Temperature (GK)
X ~2.5 uncertainty(from x 10)
29P(p,)30S29P(p,)30S
Galaviz et al.
Preliminary
(Ozel Nature 441 (2006) 1115)
Example: understand bursts to constrain NS
X-ray bursts from EXO0748−676:• O,Fe absorption lines ( redshift)• Tc/Fcool ( ~surface area)• Eddington luminosity
X-ray bursts from EXO0748−676:• O,Fe absorption lines ( redshift)• Tc/Fcool ( ~surface area)• Eddington luminosity
XH=0.661
2
erg/
g/s/
1e1
7
XH=0.55
XH=0.29
Mass uncertaintieswithin AME95Brown et al. 2002
Masses for key waiting points
150
Sp needed (withest. uncertaintyin keV from Coulomb shift)
ISOLTRAP
CPT
LEBIT
Future trap measurements: 65As,66Se,70Kr,74Sr Mass measurements with reactions: 69Br, 73Rb
Future trap measurements: 65As,66Se,70Kr,74Sr Mass measurements with reactions: 69Br, 73Rb
180
160
100
100
100
160
Current effective lifetime uncertainties from masses:64Ge: up to x2068Se: up to x472Kr: up to x2
Current effective lifetime uncertainties from masses:64Ge: up to x2068Se: up to x472Kr: up to x2
N=Z
Nuclear physics needed for rp-process:
0 12
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
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)Sb (51)
Te (52) I (53)
Xe (54)
some experimental information available(most rates are still uncertain)
Theoretical reaction rate predictions difficult neardrip line as single resonances dominate rate:
Hauser-Feshbach: not applicable
Shell model: available up to A~63 but large uncertainties (often x1000 - x10000)
(Herndl et al. 1995, Fisker et al. 2001)
Need radioactive beams
• -decay half-lives• masses• reaction rates mainly (p,), (,p)
(ok)
(in progress)
(just begun)
Summer research project of NSCL graduate student Matt Amthor at LANLprior to his NSCL thesis experiment to determine rp-process reaction rates
Opportunities for students
Simulated Light Curves from Kepler
0.5
0.7
0.9
1.1
1.3
1.5
1.7
0 5 10 15 20 25 30
Time from start of Burst (s)
Bu
rst
Lu
min
os
ity
(1
0^
38
erg
/s)
Low Rates/Burst 2
High Rates/Burst 2
Simulated Light Curves from Kepler
0.5
0.7
0.9
1.1
1.3
1.5
1.7
0 5 10 15 20 25 30
Time from start of Burst (s)
Bu
rst
Lu
min
os
ity
(1
0^
38
erg
/s)
Low Rates/Burst 2
High Rates/Burst 2
30S(p,g)* 31Cl
36K(p,g)** 37Ca
40Sc(p,g) 41Ti
46Cr(p,g) 47Mn
Vary by factor 100
M. Amthor, A. Heger, H. Schatz, B. Sherrill
Comparable to observed differences
97-98
2000
Precision X-ray observations(NASA’s RXTE)
Need precise nuclear datato make full use of high quality observational data
Example: determine accreted hydrogen mass fraction by comparing model with observations distance estimate Stringent EOS constraints (Oezel 2006)
GS 1826-24 burst shape changes ! (Galloway 2003 astro/ph 0308122)
Observables of nuclear processes in X-ray bursts: Lightcurve
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