Nucleosynthesis and gamma-rayemission in nova explosions

Alain COC

CSNSM, Orsay, France

Nova nucleosynthesis

Progress in 17O and 18F nucleosynthesis

Progress in 22Na, 26Al and 30P nucleosynthesis

Why study classical novae ?

• Nucleosynthesis

15N and 17O origin and 7Li and 13C contribution

• Gamma ray astronomy (INTEGRAL, future ACT)

Potential source of 7Be (478 keV), 18F (511 keV),22Na (1.275 MeV) and 26Al (1.809 MeV)

• Presolar grains in meteorites

•Frequency

Novae SNIIEjected mass ~ 10-5 ~ 10 M

Frequency ~ 30 ~ 10-2 (y -1 galaxy -1)Luminosity ~ 105 ~ 1011 LNucleosynthesis ≤ S ∼Fe (+ «r»)

Classical novaeAccreting binary system : a White Dwarf and a normal star:

White Dwarf (M < 1.35 M) : remnant of the evolution of stars with massMZAMS < ~ 10 M stabilized by the pressure of degenerate electrons.

H rich mater

1. Accretion of mater (H) fromcompanion (Maccr. = 10-4 -10-6 M,Δt=103-4 years)

2. Mixing with White Dwarf mater(C,O or O,Ne,….) → CNO cycle

3. Burning (TNR) starts at base ofenvelope (degenerate)

4. Nucleosynthesis in convectiveenvelope (T∼100 MK, Δt∼100 s)

5. Envelope expansion and ejection(Δt∼1 year)

Nova scenario

White Dwarf (C,O or O,Ne)

Questions :

A. Mixing mechanism ?

B. Ejected mass ? Nova Cygni 1992

CONVECTION

tconv. ≈ tnucl

Temperature

TMAX

Mr= « mass coordinate »Expanding envelope (10-6-- 10-4 MSun.)

Whi

te D

war

f≈

1 M

Sun

X =

« m

ass f

ract

ion

»

Courtesy J. José

Important reactions in nova nucleosynthesis

Parametrized models [e.g. van Wormer et al. 1994] Semi-analytical model [Coc et al. 1995] Post-processing of hydrodynamic calculations[Iliadis et al. 2002, Parete-Koon et al. 2003, Moazen et al.2007,…] Full 1-D hydrodynamic model of José and Hernanz 1998 :

• Hot CNO [Coc, José, Hernanz & Thibaud 2000 (CJHT00)]• NeNa-MgAl region [José, Coc & Hernanz 1999 (JCH99)]• “Heavy” elements [José, Coc & Hernanz 2001 (JCH01)]

Investigation of individual nuclear reactionsuncertainties with :

Time to review the experimental progress made

Nova models [José & Hernanz 1998]

4100310024002700160019001200VEJECT (km/s)

325245220205200170150TMAX (106 K)

0.441.41.91.34.72.36.4MEJECT (10-5 M)

1.351.251.151.151.01.00.8MWD (M)

ONeONeONeCOONeCOCOType/composition

White Dwarf initial composition :• CO nova : 12C and 16O• ONe nova : 16O and 20Ne with some 23Na, 24,25Mg, 27Al

Hot pp nucleosynthesis (7Be and 7Li nucleosynthesis in novae)

Production : from accreted 3He(~10-5) through 3He(4He,γ)7Bereaction competing with3He(3He,2p)4He

Destruction : by 7Be(p,γ)8B atlow temperature but protectedby 8B(γ,p) 7Be above T≈108 K(photodisintegration).

7Be and γ-ray astronomy 7Li origin1. Big-Bang (together with H, D

and 3He)2. Spallation by cosmic rays3. Stellar source (AGB, novae,..)

Hernanz, José, Coc & Isern 1996

Prompt γ-ray emission atE ≤ 511 keV from 18F βdecay and e+ annihilation

Origin of 17O

• 16O seed in CO and ONenovae

• Large nuclear uncertainty(JCHT00) on 18F (and 17O)yield(s) from :

18F(p,α)15O

17O(p,γ)18F and17O(p,α)14N

17O and 18F nucleosynthesis(Hot-CNO)

• Main uncertainty from 183 keVresonance (ΓT, Γγ [Rolfs et al. 1973],Γp upper limit [Landré et al. 1989],(ωγ)αγ known [Tilley et al. 1995] usedin NACRE and CJHT00

• Factor of ~10 uncertainty on 18F

17O+p reactions (I)

Many new experiments :

•ER= 183.2±0.6 keV [Chafa et al. 2005,2007]; also Fox et al. 2005, Moazen etal. 2007

•(ωγ)pα = 1.6±0.2 meV [Chafa et al.2005, 2007] also Newton et al. 2007;Moazen et al. 2007

•(ωγ)pγ= 1.2±0.2 µeV [Fox et al. 2004,2005]; also 2.2±0.4 µeV [Chafa et al.2005, 2007]

17O+p reactions (II) Importance of 65 keV resonance innovae and red giants!

(ωγ)pα = (4.7±0.8)×10-9 eV deducedfrom Blackmon et al. 1995 measurement

Trojan Horse method in Catania[Sergi et al., poster]

17O(p,γ)

17O(p,α)

Relative contributions to rates

Spectroscopy of 19Ne [Utku et al. 1998]

Direct measurements of 3/2- 330 […,Bardayan et al. 2002] and 3/2+ 660 keV[Coszach et al. 1995,… ] resonances at ORNL(Oak Ridge) and LLN (Louvain-la-Neuve)

Importance of low energy, 8and 38 keV 3/2+ resonances

A factor of 300 uncertainty in18F yield and gamma ray emission(in 2000)

18F+p reactions in 2000

1) 8 and 38 keV 3/2+resonance strengths ?

2) Interferences between thefour 3/2+ resonances ?

18F(p,α)15O

Transfer reaction experiments (I)

Study of the 3/2+ 6.497 and 6.528 MeV19F levels assumed [Utku et al. 1998] tobe the analogs of the 6.419 and 6.449MeV 19Ne levels corresponding to the yetunobserved 8 and 38 keV resonances

d (18F, p) 19F* α + 15N

LLN

ORNL

D(18F,pα)15N transfer reaction experiments (II)

LLN

ORNL

14 MeV at LLN (Louvain-la-Neuve)or 108 MeV at ORNL (Oak Ridge)isotopically pure 18F beams of ~106 pps

~100 µg/cm2 CD2 targets

Silicon strip detectors

Internal energy calibration

One of the two 3/2+ levels is dominant

C2S (6.497+6.528) ≈ 0.17 (LLN) [de Sérévile etal. 2003; 2007] but 6.528 MeV preferred

C2Sl=0 (6.497) = 0.11±0.04 C2Sl=0 (6.528)~0(ORNL) [Kozub et al. 2005; 2006]

Analog level assignment in 19Ne ?

6.419 and 6.449 MeV 19Ne levels cannot beneglected and can interfer with higher 3/2+ levels

CH2

18F

α

15O

LEDA 1 LEDA 2

Al

Interference study : H(18F,α)15N experiment (I)

= 110 min) :

Louvain la Neuve :• Beam : 13.8 MeV 18F, ~106 pps,18O/18F < 0.5% 17 bunches of ~2hover 1½ week

• Target : CD2 ≈ 70 µg/cm2

• Degrader : Al (95, 500, 670 mg/cm2)→ Ec.m. = 726, 665, 485, 400 keV

• Detection : LEDA silicon strip

• Normalisation : elastic scattering18F+12C in LEDA2 and CD2stoechiometry

[de Séreville et al., submitted]

Coincidences LEDA1 x LEDA2

→ very clean selection of events

Ecm = 485 keV → 180 eventsEcm = 400 keV → 35 events

Interference study : H(18F,α)15N experiment (I)

[de Séreville et al., submitted]

Interference study : H(18F,α)15N experiment (II)

Er = 665 keV, R-matrix

Good agreement with the Er = 665 keV resonance parameters Good agreement with previous experimental data

ORNL [Bardayan et al. 2002]

LLN [de Séreville et al., submitted]

Interference study : 3/2+ levels

• Which one of the two (8 or 38 keV) resonance is contributing most ?

• Parametrisation from λ=0 (pure 8 keV) to λ=1 (pure 38 keV)

• Three levels R-matrix calculations

• Influence of R matrix radius !

[de Séreville et al., submitted]

Interference study : reaction rates

New 18F(p,α) upper and lower rate limits :

• Three level interferences

• Dominant 3/2+ 8 or 38 keV resonance

(Relative to CHJT00)

1/2+ level contributions

Dufour & Descouvemont (2007)

Microscopic two cluster modelprediction of 1/2+ levels :• Broad EX = 7.8 (ER ≈ 1.4 MeV), analogof 8.65 MeV in 19F, single particle stateas 3/2+ at 7.07MeV

• Below threshold

Would affect 18F(p,α) rate at nova T !

EX = 7.420 MeV[Bardayan et al. 2004](ER ≈ 1. MeV) but assigned to 7/2+ or 5/2+

19Ne spectroscopy at LLN

Inelastic scattering experiment : 19Ne(p,p’)19Ne*→α+15O

ΔE - E

ΔE – E(CD PAD)

CH2

19Ne p

19Ne

α

• Beam : 171 MeV 19Ne

• Protons detected at 0°

• α in coincidence

EX~7.89 MeVΓ~200 keV

EX~7.89 MeVPROVISIONALDalouzy, de Oliveira Santos et al.

EX=7.61 MeV3/2+

•26Alg from 24,25Mgand 23Na seeds

25Al(p,γ)26Si26Alg(p,γ)27Si (?)

•22Na from 20Ne seed21Na(p,γ)22Mg22Na(p,γ)23Mg

22Na and 26Alg

production /destruction

Improvements in 22Na related reaction rates21Na(p,γ)22Mg : EX(ER) = 5.714, 5.837, 5.962 Mev levels wereassumed to contribute to rate at nova T

TRIUMF-ISAC : 21Na beam, gas target, BGO array and DRAGONrecoil spectrometer →direct resonance strength measurements

ER = 206 keV (EX=5.714) resonance , ωγ = 1.03±0.16±0.14 meV[Bishop et al. 2003] dominates over others [D’Auria et al. 2004].

22Na(p,γ)23Mg : Gammasphereexperiment [Jenkins et al. 2004],trough 12C(12C,n)23Mg and23Al β decay [Iacob et al. 2006]→improved 23Mg spectroscopy

25Al(p,γ)26Si : Orders of magnitude uncertaintiesfrom missing 3+(l=0) and 4+ 26Si levels in 2000

26gAl(p,γ)27Si : main uncertaintyfrom ER=188 keV resonancestrength 55±9 µeV [Vogelaar 1989,but unpublished]TRIUMF ~109 26gAl beam (~1015

26gAl total) → 119 27Si (DRAGON)and γ (BGO) coincidencesωγ = 35±4stat±5sys µeV[Ruiz et al. 2006]

Improvements in 26Al relatedreaction rates

Missing levels investigated by Bardayan et al.,2002; 2006; Caggiano et al. 2002; Parpottas et al. 2004;Seweryniak et al. 2007

(From Mg-Al)

Si-Arnucleosynthesis

No “seed” nuclei above Al

Leaks out of the Mg-Al“cycle”

Depends on 30P(p,γ)31S rate

30P halflife : 2.5 mn

“Heavy elements”production

Isotopic 28,29,30Sicomposition of somepresolar grains [Amariet al. 2001]

30P(p,γ)31S rate No measured resonances

Poor 31S spectroscopy

Rate from statistical(Hauser-Feshbach) model,inappropriate for this A and T

Factor ~100 uncertainty (?) Improved spectroscopy byJenkins et al. 2005; 2006;Kankainen et al. 2006; Ma etal. 2007; Wrede et al. 2007Rate ~H.F. but no measuredωγ or C2S No 30P beam !

•Classical novae are primary objectives for gamma-ray astronomy

•New way to constrain nova models : isotopic grain composition

• Nuclear physics of novae

Recent experimental progress for many important reactions :21Na(p,γ), 22Na(p,γ), 23Na(p,γ), 25Al(p,γ), 17O(p,γ), 17O(p,α),….

Recent progress for the 18F(p,α) important reaction but muchremains to be done experimentally : TRIUMF and RIKEN

Further experimental investigation of the 30P(p,γ)31S reaction

Conclusions

Novae will become the first explosive site where all nuclear reactionrates are derived from experimentally measured cross sections !

Main collaborators and contributors

J. José, M. Hernanz (Barcelona) ,

N. de Séréville, F. Hammache (Orsay),

C. Iliadis (TUNL),

C. Spitaleri, S. Cherubini and collaborators (Catania),

F. de Oliveira Santos, J.C. Dalouzy (GANIL),

P. Descouvemont (Bruxelles),

C. Angulo (Louvain-la-Neuve)