FIVE REGIMES OF NUCLEAR BURNING IN DENSE STELLAR MATTER
description
Transcript of FIVE REGIMES OF NUCLEAR BURNING IN DENSE STELLAR MATTER
FIVE REGIMES OF NUCLEAR BURNING IN DENSE STELLAR MATTERFIVE REGIMES OF NUCLEAR BURNING IN DENSE STELLAR MATTER
D.G. Yakovlev
Ioffe Physical Technical Institute, St.-Petersburg, Russia
Thermonuclear burning
Physical conditions
Summary
Moscow, December, 2004
Screening in thermonuclearreactions
Pycnonuclear burning
General outlook and applications
PHYSICAL CONDITIONS
i
ippp
mL
i
m
neZT
Ta
eZT
na
aT
eZ
22
22
3/122
4,
175;1
.4
3,
...21 cZZZ
PHYSICAL STATES OF IONS
Gas Strongly coupledclassical system
Strongly coupledquantum system
1
22
a
eZT
1
22
a
eZTp
1
22
a
eZT p
Classical theory of thermonuclear reactions
...21 cZZZ
Reaction rate:
scm
reactions3
12
21
1
v
nnR
)(/3
0
Evv TE
ed
Z1 Z2
exp)(,)()(
EPE
EPESE
v
eZZrprE
a
b
2212
)(d2
Classical theory of thermonuclear reactions
-expT
ES
M
Ev pkpk )(
3
24
12
2733/1
2
422
21
2
T
eZMZ
T
Epk
Reaction rate R depends mainly on T
History
Example
G. Gamow, H. Bethe, C. Critchfield, E. Salpeter,
C. Von Weizsacker, A. Cameron, W. Fowler, G. Rivers
Carbon burning: ...MgCC *241212 Rnt i /,cmg10 3-9 = burning time
T=109 K t~ 1 min
T=108 K t~1036 yr No burning at low T!
Nobel Prize, 1967
1938
PLASMA SCREENING IN THERMONUCLEAR REACTIONS
)()(2
21 rr
eZZrU
Created byneighbors
ar ~
Consider: pt TTar
Then trrconstr for )(
Two-stage process: (1) approaching the barrier(2) penetrating the barrier
The reaction rate: R=R0E
E>1 enhancement factor
TffffE j
j
),exp( 1221
Basic ideas:Salpeter 1954, 1961Salpeter & Van Horn 1969 DeWitt, Graboske & Cooper 1973
Thermodynamic function
STRONG PLASMA SCREENING
122
pTTa
eZ Thermonuclear regimewith strong screening
1exp 1221 fffE
1for 9.0)(with
Carlo, Monte OCP from - )(
4
3,,
)( :rule additive;
3/1
3/122
f
f
naZaa
Ta
eZ
ffT
f
eeej
j
jj
jjj
j
+ 1
Salpeter’s model:
1 and for )057.1exp( 21 ZZE
21 ZZ
1 2 12
Pycnonuclear reactions
exp)(,)()(
EPE
EPESE
6/1
2
0
1)(d
2
r
drprE
a
b
Coulomb lattice of nuclei, T=0 d
Zero-point vibrations,
m
rE
~,~ 0
m
neZ ip
224~
=ion plasma frequency
WKB tunneling:
?1~
The reaction rate exponentiallyincreases with growing density!
PYCNONUCLEAR BURNING OF DENSE STELLAR MATTERPYCNONUCLEAR BURNING OF DENSE STELLAR MATTER
tburn~1075 yrs tburn~0.1 s
Gamow and Wildhack
Later History
Zel’dovich (1957)
Cameron (1959)
Kirzhnits (1960)
Kopyshev (1964)
Wolf (1965)
Van Horn (1966)
Salpeter & Van Horn (1969)
Schramm & Koonin (1990)
Err-brr-mrr!!
THERMALLY ENHANCED PYCNONUCLEAR BURNING
Increase T from T=0: )0(/)( RTREpyc = enhancement factor
Salpeter and Van Horn 1969
a
eZ
Ta
eZE
T
EfnE
pk
nnn
220
22
0
exp
1exp;2
1
INTERMEDIATE THERMO-PYCNONUCLEAR BURNING
const)( ;Z
~;~ ;~22
ra
eEarTT pktp
Most difficult for the theory!Many attempts!
FIVE REGIMES OF BURNING IN DENSE MATTER
Thermonuclear
Intermediate
Pycnonuclear
Cla
ssic
al
Str
on
g
scre
enin
g
T-e
nh
ance
d
T=
0
1 2
3
4 5
TEMPERATURE DEPENDENCE
GENERAL OUTLOOK
CARBON IGNITION CURVE
1. Accreting massive white dwarfs -- SNIa
2. Accreting neutron stars -- superbursts
Applications of pycnonuclear burning
White dwarfs and neutron stars (particularly, accreting)
Mas
s de
nsit
y, g
cm
-3
106
109
1010
1012
1013
HHe
C
ASHES
BURN!
No hydrogen in WDsWDs as SN IaX-ray bursters
Accreting neutronstars – soft X-raytransients
48Mg+48Mg -> 96CrDeepest burning:
SUMMARY
1. There are five regimes of nuclear burning 2. Classical thermonuclear regime is well elaborated; other regimes – much less 3. The problem belongs to the physics of strongly coupled Coulomb plasma: quantum tunneling in random and fluctuating plasma potential 4. Theory goes back in time!