# Presentation: 125074

## The rp process in X-ray bursts  astrophysics and experiments with fast radioactive beams 

**H. Schatz  **
**Michigan State University **
**National Superconducting Cyclotron Laboratory**
**Joint Institute for Nuclear Astrophysics**

- The rp process in X-ray bursts  astrophysics and experiments with fast radioactive beams

## Slide 2

## X-ray bursts 

- 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)

## Precision X-ray observations(NASA’s RXTE)

**Galloway et al. 2003**

**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

-  GS 1826-24 burst shape changes !     (Galloway 2003 astro/ph 0308122)

**Reality check: Burst comparison with observations**

- For example to determine XH  distance, EOS

**Notes:**
Not talking about understanding every little detail, but about taking observations and making full use of them
SHWN THAT THERE IS LINK BETWEEN observation and nuclear physics – nuclear physics not good enough
Slight increase in accretion rate observed

## ?

-  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 ?

- Likely no nucleosynthesis contribution
- Goal: understand systems and neutron stars

## Reaction rates:

- 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

## Why measuring excitation energies ?

- Coulombpenetrability

- Boltzmann e-E/kT

- 32Cl(p,g)33Ar Reaction rate for T=0.4 x 109 KExample: contribution from one individual resonance (5/2+)

## 33Ar

**Focal plane:****identify ****33****Ar**

**Plastic target**
**34****Ar ****(p,d) ****33****Ar**

**Radioactive ****34****Ar beam****84 MeV/u T****1/2****=844 ms****(from 150 MeV/u ****36****Ar)**

**33****Ar**

**34****Ar**

**Beam****blocker**

**n-removal related to astrophysical ****32****Cl+p ******** ****33****Ar+********rate**

- -rays from predicted 3.97 MeV state

- Doppler corrected -rays in coincidence with 33Ar in S800 focal plane:

**SEGA**

## 32Cl(p,)33Ar

**x 3 uncertainty**
**(from x 1000)**

- New rates: Clement et al. PRL 92 (2004) 2502, Galaviz et al.

**33****Ar**

**33****Ar**

**S****p**** 3343(8)**

**SM ****(Brown)**

**Exp**

**3970 5/2****+**

******104(6) keV**

******150(4) keV**

**3560 7/2****+**

- reaction rate (cm3/s/mole)

**Clement et al. **

- Ex by

**32****Cl+p**

-  Rate dominated by capture on low lying (90 keV)     first excited state in 32Cl

- 32Cl(p,)33Ar

## Stellar Enhancement Factor

**H. Schatz**

- 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

## Reach of method

_**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

**Nuclei that can ****be studied at ****NSCL**

**Clement et al. PRL92,17502 (2004)**
**Schatz et al. PRC72, 065804 (2005)**

**Program continued by ****D. Galaviz**
**M. Amthor**
**A. Chen**

**HIRA experiments****with 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)

## New rates: Clement et al. PRL 92 (2004) 2502, Galaviz et al. 

**x 3 uncertainty**
**(from x 1000)**

- New rates: Clement et al. PRL 92 (2004) 2502, Galaviz et al.

**33****Ar**

**33****Ar**

**S****p**** (3343)**

**SM ****(Brown)**

**Exp**

- 32Cl(p,)33Ar

**3970 5/2****+**

******104(6) keV**

******150(4) keV**

**3560 7/2****+**

- reaction rate (cm3/s/mole)

**Clement et al. **

- Ex by

**32****Cl+p**

## (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

## 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

- 180

- 160

- 100

- 100

- 100

- 160

- Current effective lifetime uncertainties from masses:	64Ge: up to x20
- 	68Se: up to x4
- 	72Kr:  up to x2

- N=Z

##  Need radioactive beams

- _Nuclear physics needed for rp-process:_

- 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)

- (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)**

## Opportunities for students

| 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

## Slide 20

## Slide 21

**Notes:**
Say something about crust comp

## Precision X-ray observations(NASA’s RXTE)

**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

**Notes:**
Not talking about understanding every little detail, but about taking observations and making full use of them
SHWN THAT THERE IS LINK BETWEEN observation and nuclear physics – nuclear physics not good enough
Slight increase in accretion rate observed