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V.S.Imshennik, O.G.Ryazhskaya
A Rotating Collapsar
And
Possible Interpretation
Of The LSD Neutrino Signal
From SN 1987A
The work deals with a possible explanation of the results, obtained by underground
detectors during Supernova SN1987A explosion.
The name "SN" came from the observational astronomy data and deals with an instant appearance of a very bright star, with luminosity of about tens millions of the solar one.
Indeed, this is not the birth of a new star, but the destruction of the star, exhausted its nuclear fuel.
During the lifetime of the star (its evolution) nuclear forces as well as gravitational, rotating and magnetic field forces act on it.
The simplest case: the star is spherically symmetric, non-rotating, non-magnetic.
Stable state:The forces of hot gas pressure compensate the gravitational ones. The temperature of the hot gas is supported by the nuclear radiation. Fn=Fg
In the beginning of its evolution the star consists mainly of hydrogen. During the time due to the nuclear synthesis reaction
Fn
Fg
The forming of Fe nuclei takes place in the core Fn<Fg . The star starts to compress, to collapse. Fe - nuclei are destroyed, electrons are practically pressed in the atomic nuclei under the action of gravitational forces. The electron neutrinos are emitted.
Total energy 2%10 cM star 10 % energy of state
the energy which keeps the star in equilibrium is released. After the production of Fe nuclei, the further evolution requires the energy consumption.
~60 years ago the problem looked like the science fiction mixed with a some joke.
On April 1st, 1941 Phys. Rev. has published «Neutrino Theory of Stellar Collapse» by G.Gamov and M.Schoenberg
«The processes of absorption and reemission of free electrons by atomic nuclei which are abundant in stellar matter may lead to such tremendous energy losses through the neutrino emission that the collapse of the entire stellar body with an almost free-fall velocity becomes quite possible»
~
1
1
eNN
NeNA
ZA
Z
AZ
AZ URCA-process
The idea was born in Rio casino “Urca” where it was possible to lose a lot of money very quickly.
«We have developed the general views regarding the role of neutrino emission in the vast stellar catastrophes known to astronomy, while the neutrinos are still considered as highly hypothetical particles because of the failure of all efforts made to detect them».
G.Gamov, M.Schoenberg
e
e
epn
nep
~
1957 F. Reines and C. Cowan detect antineutrinos from reactor.
1959 An active discussion of the role of neutrinos in astrophysics starts. B. Pontecorvo states, that e-scattering may lead to macroscopic effects.
1965 Ya.B. Zel’dovich and O.H.Guseinov show, that gravitational collapse is accompanied by powerful and short (~10 ms) pulse of neutrino radiation.
1965 The first proposal to search for collapsing starts (c.s.) using neutrino detectors by G.V.Domogatsky and G.T. Zatsepin
1965 The birth of an experimental neutrino astrophysics.
1964-1966 W. Fowler, F. Hoyle investigate the role of neutrinos in the last stages of stellar evolution. The dissociation of iron core plays an important role in stability loss by massive stellar envelopes.
1966 The first calculation of collapse dynamics by S. Colgate, R.White
1966-1967 The process of an implosion for stars with 32; 8; 4; or 2 solar masses has been studied. The parameters of neutrino radiation are obtained (W. Arnett).
1967-1978 The structure of neutrino burst , energy spectra was studied by V.S.Imshennik, L.I.Ivanova, D.K.Nadyozhin, I.V.Otroshenko (Model I) in the first time . Also it was shown that the main flux of the neutrinos is emitted during the cooling stage of a new born neutron star. The duration of neutrino pulse was shown to be ~ 10 s.
1980-1982 The time structure and energy spectra of for the initial stage of collapse (<0.1 ms)
are obtained by R.Bowers, J.Wilson (Model II).
1987 S. Bruenn’s calculations
ee ~and
,,,~ee
Neutrino detection from a collapsing star makes it possible:
- To detect gravitational collapse even it is “silent” (isn’t accompanied by Supernova explosion);- To investigate the dynamics of collapse;- To estimate the temperature in the star center.
If the star is nonmagnetic, nonrotating, spherically symmetrical the parameters of neutrino burst are the following (Standard model):
ModelModel
Total Total energy,energy,
Total Total energy of energy of
Total Total energy of energy of
Duration, Duration, ss
Model IModel I
3-143-14 0.5-2.30.5-2.3 0.10.1
12.612.6 10.510.5 -- ~~2020
Model IIModel II
1010 88 2525 55
erge5310,~ erge
5310,MeVE
e,~ MeVE
e,
MeV
Е e )(
From the theory of the Standard collapse it follows that the total energy,carried out by all types of neutrinos , corresponds to ~ 0.1 of star core mass and is divided among these 6 components in equal parts.
~,,~,,~, ee
erg5310
Until now, Cherenkov (H2O) and scintillation (СnH2n) detectors which are capable of detecting mainly , have been used in searching for neutrino radiation, This choice is natural and connected with large -p cross-section
As was shown at the first time by G.T.Zatsepin, O.G.Ryazhskaya, A.E.Chudakov (1973), the proton can be used for a neutron capture with the following production of deuterium (d) with - quantum emission with 180 – 200 µs.
2.2n p d E МэВ
2 44 2~ 9.3 10e p e
E см
e~
e~
nepе ~
General idea
How can one detect the neutrino flux from collapsing stars?
The specific signature of event
MeVE 2.2
MeVEe
5.0
How can the neutrino burst be identified ?
T
The detection of the burst of N impulses in short time interval T
i Ethr
iiiMdEEEI
RN )()(
4
1~
2
А
t
The possibility to observe the neutrino burst depends on background conditions
1. Cosmic rays 0<E< а) muons б) secondary particles generated by muons (e,,n and long-
living isotopes) с) the products of reactions of nuclear and electromagnetic
interactions2. Natural radioactivity Е<30 MeV, mainly Е<2.65 MeV а) , b) n, (n ), U238, Th232 c) , (n) d) Rn222
1. Deep underground location2. Using the low radioactivity materials 3. Anti-coincidence system4. Using the reactions with good signature5. The coincidence of signals in several detectors
The source of background:
Background reduction:
Develop new models of collapse
Experimentalists
The theory predicts the possibility of gravitational collapse without envelope drop (without supernova appearance) once per 10 yrs.
5 supernovae were observed in Our Galaxy:
1604 (Kepler) 1572 (Ticho Brage)11811054 (Crab Nebula)1006
Theoreticians
Develop registration methods
Due to these events are very rear the detectors should operate with a maximum time and should be multipurpose ones (underground observatories).
1977 Arteomovsk Scintillation Detector (INR RAS) has scintillator mass of 105 t, good signature of events (the possibility to detect both particles in the reaction)
1978 Baksan Underground Scintillation Telescope (INR RAS) with a total mass of 330 t
1984 LSD – (Liquid Scintillation Detector, USSR – Italy), scintillator mass - 90 t, good signature of events (the possibility to detect both particles in the reaction : )
*dpn
nep
МэВEd 2.2
nep~
MeV
ArteomovskBST
Soudan
KamiokaGran Sasso
HomestakeMt Blanc
Sudbury
KGF
The muon depth-intensity curve (underground data): curves are calculated by Bugaev et al., 1998
The large volume detectors are the underground observatories for:
- Neutrino astrophysics
- Cosmic Rays physics
- Search for point sources of cosmic rays
- Study of neutrino oscillations
- Search for rare events predicted by the theory (proton decay, monopoles, dark matter...)
- Geophysical phenomena
Neutrinos from collapsing stars
)~(
)~(
)~(
ee
P,, A
0 0, , ,,
K Kp n
eEAS
Muon beams
, ,( )
. .эл мeливни
( )
Hadronic shower
0, ,,
адронныйКливеньp n
,( ),
?
Neutrinos from point sources
em. shower
s
Solar neutrinos
hadronic shower
It is possible to study cosmic rays underground using their penetrating component
February 23, 19872 h 52 min.
# of# of eventevent
TimeTime, , UTUT±2ms±2ms
Energy,Energy,MeVMeV
11
22
33
44
55
2:52:36,792:52:36,79
40,6540,65
41,0141,01
42,7042,70
43,8043,80
6,2 – 76,2 – 7
5,8 – 85,8 – 8
7,87,8 –11–11
7,0 – 77,0 – 7
6,8 – 96,8 – 9
11
22
7:36:00,547:36:00,54
7:36:18,887:36:18,88
88
99
Events, detected by LSD
February,23, 1987 г. (SN 1987 A)
On February,23, 1987 A Supernova explosionin the Large Magellanic Cloud
occured.
+4
+6
+8
+10
+12
0h 2h52m 7h36m 9h22m 15h54m
Sk – 69o202
McNaught
Radio (21cм)
?
Shelton Jones
DiscoveryJones
Mont Blanc
Kamioka,IMB,
Baksan S W(У В)
1987А
mv
UTFeb24 Feb25
Shelton
DetectorDepth,
meters of water
equivalent
Fiducial volume,
tons
Material Energy
threshold, MeV
Detection
efficiency Background rate
s-1е+ spectrum
of reactionе- spectrum of reaction
BUST
USSR 850130
(200)
160
CnH2n
Fe
10 0.6 0.15
(0.54)
0.013
(0.033)
LSD
USSR –
Italy
520090
200
CnH2n
Fe
5-7 0.9 0.4(0.7) 0.01
KII
Japan –
USA
27002140 H2O 7-14 0.7 0.17
(0.54)
0.022
IMB
USA 15705000 H2O 20-50 0.1 0.02
(0.18)
3.5x10-6
nepe~ ee ii
Kamiokande
BaksanIMB
LSD
February 23, 1987
Optical
Geograv
LSD
KII
IMB
BUST
1 3 5 7
2:52:35,4
2:52:34
2:52:34
7:36:00
7:35:35
7:35:41
7:36:06
44
43,8 19
47
:47
21
5
2(4)
1 6
2
12
8
v m =6vm =12 m
observations
2:52:36,8
m
9 11
February 23, 1987
1 3 5 7 9 11
mv=6mmv=12m
Geograv
LSD
KII
IMB
BUST
2:52:35,42:52:36,8
43,82:52:3
444
2:52:34
7:36:00
7:35:35
7:35:41
7:36:06
19474721
2
12
8
6
5
2
1
(4)
The detector responses to the standard stellar collapse in the Large Magellanic Cloud
DetectorDetector
LSDLSD
BUSTBUST
KIIKII
IMBIMB
1.51.5
22
1717
66
0.0430.043
0.0520.052
0.530.53
0.40.4
0.0240.024
0.0360.036
0.360.36
0.350.35
)1(eK )2()2( baK
e )2( bK
e
)(1
~)(~
2
211
~2
kT
ЕеMeVsФ
MeVkT 2~
LSDLSD BUSTBUST KIIKII IMBIMB
1.71.7
2.12.1
0.10.1
0.10.1
2.12.1±1.0±1.0
1.8±0.81.8±0.8
55
55
0.20.2
0.50.5
55±2.5±2.5
12±612±6
00
00
MeVkT ,эрг
We
,1054~ ik
The total energy of neutrino radiation from SN1987A is more than an order of magnitude higher than the binding energy of neutron star with a baryon mass of about 2М ergWE
etot55
~ 10)21(6
if
The short review of the rotational mechanism:
On the threshold of gravitational collapse the Fе-O-C stellar core
Mt – total mass, I0 – total angular momentum
are conserved during the collapse of the core
into a rotating collapsar
The possible solution is : A rotating collapsar
The collapsar with the high probability falls into the region of the dynamical instability.
The criterion:27.0
grav
rot
Total rotational energyTotal gravitational energy
During the collapse increases greatly compared to , which is also an increasing quantity
rot grav
This instability grows with the characteristic hydrodynamic time and leads to the breakup of the collapsar into pieces.
The Two-Stage Gravitational Collapse Model[Imshennik V.S., Space Sci Rev, 74, 325-334 (1995)]
12 MM
222 , JM
12 111, JM
A rotating collapsar
~,
e
above
aside
The rotation effects make it possible:
1. To resolve the problem of the transformation of collapse into an explosion for high-mass and collapsing supernovae (all types of SN, except the type Ia – thermonuclear SN)
2. To resolve the problem of two neutrino signals from SN 1987A, separated by a time interval of 4.7 h.
Tc~5x1012
KTc~5x1010
K
The difference of neutrino emission in the standard model and in the model of rotating
collapsar.
MeVE
MeVE
MeVE
e
e
)2520(
10
12
~,,~,
~
The main reaction – URCA-process:
MeVE
nep e
)5030(
e e
e~
~
~
e
e
e
e
e
314106.2~ cmg
erg53~, 103.5 erg
eee
52~, 109.8
Let us consider how the various detectors operated during the explosion
of SN1987A could record the neutrino signals in terms of the model of a
rotating collapsar, which reduces to the following:
1. Two neutrino bursts separated by a time tgrav~5 h must exist.2. The neutrino flux during the first burst consists of electron neutrino with a total energy of 8.9х1052 erg: the neutrino energy spectrum is hard and asymmetric with mean energies in the range of 25-50 MeV; the duration of the neutrino radiation is t ~ 2.4 - 6 s.3. The second neutrino burst corresponds to the theory of standard collapse.
Liquid Scintillator Detector (LSD)
General view of LSD
Fe (2 cm)
Fe (10 cm)
H=5200 m.w.e. 72 counters 90 tons of СnH2n (n~9), 200 tons of Fe
4.5 m
8m
6 m
150 cм
100
100
PM FEU - 49B ( 15 cм)
Bugaev E.V., Bisnovaty-Kogan G.S. et al., 1979
The comparison of the total reduced cross-sections with νn cross-section on a free neutron for the reaction
*)1,(),( ZAeZAe
eCoFee56
27
56
26
1+ GT __________10,589 1+ GT __________ 7,589 1+ GT __________ 4,589 0+ IAS __________ 3,589 1+ __________ 1,72 4+ __________ Co
56
27
MeVFeECoE 056.456
26
56
27
MeVE 40
MeVeKE 84.30, MeVE 1MeVE 82.1 MeVE
n72.1
2401027.1 cm
2401005.1 cm
2411041.6 cm
2401027.1 cm
F
GT
GT
GT
0+
24024.4 cmEtot
n
eK
MeVEMeVE
MeVE
72.182.1
84.31,
E
n
eK
MeVEMeVE
MeVEMeVE
72.182.1
484.27,
Yu.V. Gaponov, S.V. Semenov
n
eK
MeVEMeVE
MeVEMeVE
72.182.1
784.24,
СnH2n
CoeFe e5656
СnH2n
CoeFe e5656
СnH2n
CoeFe e5656
MeVE 72.1
EEE oe
MeVE 82.1 MeVE 72.1
MeVE 4
MeVE 82.1
MeVE 7
e
MeVE 82.1EEE oe EEE oe
e
e
Energy spectrum of the particles, coming from 2,8 cm iron plate (Geant4 calculations; histogram – total energy deposit)
0 5 10 15 20 25 30 35 40Energy, MeV
106
105
104
103
102
10
1
Events
Energy range, detected by LSD
DetectorDetector EnergyEnergy
thresholdthreshold
Estimated number ofEstimated number of
eeAA interaction interaction
EstimatedEstimated
EffectEffect Exp.Exp.
NN11 NN22 NN33 NN44
LSDLSD 5 – 75 – 7 3.23.2 5.75.7 3.53.5 4.94.9 3.23.2 55
KIIKII 7 – 147 – 14 0.90.9 3.13.1 1.21.2 2.52.5 2.72.7 22**
BUSTBUST 1010 2.82.8 5.25.2 ~1~1 11****
2N
130 (N )e
E MeV 240 (N )e
E MeV
35 (N )e
f E with
47.5 (N )e
f E with e
kT
5.34ckT MeV
14 32.6 10 /g cm
* De Rujula, 1987 ** Alexeyev, 1987
AMANDA
Baikal
LVD
KGF
KamLANDSK
IMB
SNO
SOUD
ArteomovskLSD
Baksan
AMANDA
NEUTRINO DETECTORS
SUPER K
LVD SuperK
LVD
KamLand
SNO
DetectorDepthm.w.e
Mass,ktons
Thre-shold,MeV
EfficiencyNumber of
events Back-ground
s-1
ArteomovskASD
Russia570
0.1CnH2n
5 0.97 0.8 0.85 57 2.1 9.5 0.16
BaksanBUST
Russia
850 0.13(0.2)CnH2n
10 0.6 - 0.2 45(67)
1.4(2.2)
2.8(4.3)
0.013(0.033)
KamLAND USAJapan
27001.
CnH2n~ 4
-500 22
30054
Gran SassoLVD
Italy,Russia
3300
0.95Fe1.1
CnH2n
4 – 6 0.9 0.6 0.5-
550
470
24
300
60< 0.1
KamiokaSuper-K
Japan,USA2700
22.5H2O
5.5 0.7 - --
6000
750
220-
SNOCanada 6000
1.4H2O
1 D2O5 530
37770
C12,
eipe~ne Ae Ce
Radon peaks distribution vs time (November – March, 1997)
The counting rate of the LVD during the earthquake in Italy,
1997.Arrows mark the moments of
seismic shocks.
Neutrons generated by muons underground
0 200 400 600 μs
Number of Events
Reactions for scintillation and Cherenkov counters2n nС H 2H O
e p e n 2 44 2~ 9.3 10e p e
E см
e ee e 2 45 2~ 9.4 10eee
E см
i ie e 2 45 2~ 1.6 10iie
E см
i ie e 2 45 2~ 1.3 10iie
E см
12 12* 15.1C C МэВ 12 (15.1 )С МэВ
0.5e
E МэВ
1.3e
E E МэВ
eNCe1212
eC12
eBCe1212~
~12 eC
MeVEthr 34.17 ms9.15
MeVEthr 4.14 ms3.29
242,
242
1023.1)20(
10066.0)10(
cmMeVЕ
cmMeVE
е
ee
cm2
cm2
cm2
cm2
MeV
MeV
The simplest case
Double neutron star (NS)
Almost all of the angular momentum can turn into an orbital angular momentum, Jоrb≤Jo, J= Jo-Jоrb becomes the spin angular momentum of the NS themselves especially in the more massive component of this binary. The NS binary is formed through the hydrodynamic fragmentation of a rotating collapsar.
e – spectra of volume radiation for B-nucleonic gas + FD-electronic gas
ee p n The only reaction of URCA-processes:
Neutrino radiation luminosity per gramm(Ivanova et al, 1969; Imshennik, Nadyozhin, 1971, 1972)
,n e
p
NN kT
15
1 12
0
1 ln 2 11 exp sec
1e e
enp
qg
m ft m c kT
5 5
2
1~
1 exp1 expe
ee kT
q x
m c x
00 2.52.5 5.05.0 7.57.5 1010 2020
XXmaxmax(()) 5.0335.033 5.3035.303 6.3276.327 8.0088.008 10.0010.00 18.9718.97
Y(Y()) 5.5095.509 6.7506.750 7.2967.296 8.7578.757 10.5710.57 19.3219.32
1. Central parameter of rotating collapsar (t ~ 2.5 sec)2. Total energy of neutrino radiation (t ~ 6 sec)
(Imshennik, Nadyozhin, 1977, 1992):
2.5 10 ( ~ 10 100)c
52~ 8.9 10e e e
erg
max max~ ~ 30 50ckT x MeV
KTc10102.6
314106.2 cmgc)34.5( MeVkTc
MeV)5030(
The signal detected by LSD is
the first detection of a neutrino burst from the collapse of SN
1987A
?
The simplest case: the star is spherically symmetric, nonrotating, nonmagnetic.
Gravitational energy, the energy of nuclear radiation
George Gamow excluded completely the possibility of using 1D-spherical-symmetric collapse for explanation of SN explosion
«It is, in fact, much more likely that the lack of supporting pressure in the stellar interior will cause a very irregular motion of gas masses, some of them precipitating towards the center and other being ‘squeezed out’ and thrown away in the form of vigorous prominences»…
«The rotation of the star will exercise some kind of directing influence on this phenomenon since the presence of centrifugal force will hinder the inward motions of matter in equatorial regions». [Gamov G.: 1944, Phys. Rev., 65,20]