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. F n =F g In the beginning of its evolution the star consists mainly of hydrogen. During the time due to the nuclear synthesis reaction FnFgFnFg The forming of Fe nuclei takes place in the core F n <F g. 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 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»

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

1957 F. Reines and C. Cowan detect antineutrinos from reactor An active discussion of the role of neutrinos in astrophysics starts. B. Pontecorvo states, that e-scattering may lead to macroscopic effects Ya.B. Zel’dovich and O.H.Guseinov show, that gravitational collapse is accompanied by powerful and short (~10 ms) pulse of neutrino radiation 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 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 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) 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 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) S. Bruenn’s calculations

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): Model Total energy, Total energy of Duration, s Model I ~20 Model II 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.

Until now, Cherenkov (H 2 O) and scintillation (С n H 2n ) 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. General idea How can one detect the neutrino flux from collapsing stars? The specific signature of event

How can the neutrino burst be identified ? T The detection of the burst of N impulses in short time interval T 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 interactions 2. Natural radioactivity Е<30 MeV, mainly Е<2.65 MeV а) , b) n, (n  ), U 238, Th 232 c) , (  n) d) Rn Deep underground location 2. Using the low radioactivity materials 3. Anti-coincidence system 4. Using the reactions with good signature 5. 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) (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 : ) MeV

Arteomovsk BST Soudan Kamioka Gran Sasso Homestake Mt 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 P, , A Muon beams Hadronic shower ? Neutrinos from point sources em. showers Solar neutrinos hadronic shower It is possible to study cosmic rays underground using their penetrating component

February 23, h 52 min.

# of event Time, UT±2ms Energy, MeV :52:36,7940,6541,0142,7043,80 6,2 – 7 5,8 – 8 7,8 –11 7,0 – 7 6,8 – 9 127:36:00,547:36:18,8889 Events, detected by LSD February,23, 1987 г. (SN 1987 A)

On February,23, 1987 A Supernova explosion in the Large Magellanic Cloud occured.

h 2 h 52 m 7 h 36 m 9 h 22 m 15 h 54 m Sk – 69 o 202 McNaught Radio (21cм) ? Shelton Jones DiscoveryJones Mont Blanc Kamioka, IMB, Baksan S W (У В) 1987А mvmv UT Feb24 Feb25 Shelton

Detector Depth, meters of water equivalent Fiducial volume, tons MaterialEnergy threshold, MeV Detection efficiency Background rate s -1 е + spectrum of reaction е - spectrum of reaction BUST USSR (200) 160 C n H 2n Fe (0.54) (0.033) LSD USSR – Italy C n H 2n Fe (0.7)0.01 KII Japan – USA H2OH2O (0.54) IMB USA H2OH2O (0.18) 3.5x10 -6

Kamiokande Baksan IMB LSD

February 23, m v =6 m m v =12 m Geograv LSD KII IMB BUST 2:52:35,4 2:52:36,8 43,8 2:52: :52:34 7:36:00 7:35:35 7:35:41 7:36: (4)

The detector responses to the standard stellar collapse in the Large Magellanic CloudDetector LSDBUSTKIIIMB LSDBUSTKIIIMB ± ± ±2.5 12±600 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  if

The short review of the rotational mechanism: On the threshold of gravitational collapse the Fе-O-C stellar core M t – total mass, I 0 – 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: Total rotational energy Total gravitational energy During the collapse increases greatly compared to, which is also an increasing quantity 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, (1995)] A rotating collapsar 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.

T c ~5x10 12 K T c ~5x10 10 K The difference of neutrino emission in the standard model and in the model of rotating collapsar. The main reaction – URCA-process:

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 t grav ~5 h must exist. 2. The neutrino flux during the first burst consists of electron neutrino with a total energy of 8.9х10 52 erg: the neutrino energy spectrum is hard and asymmetric with mean energies in the range of MeV; the duration of the neutrino radiation is t ~ 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 counters90 tons of С n H 2n (n~9), 200 tons of Fe 4.5 m 8m8m 6 m

150 cм 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 + GT __________10, GT __________ 7, GT __________ 4, IAS __________ 3, __________ 1, __________ F GT 0+0+ Yu.V. Gaponov, S.V. Semenov

С n H 2n e e e

Energy spectrum of the particles, coming from 2,8 cm iron plate (Geant4 calculations; histogram – total energy deposit) Energy, MeV Events Energy range, detected by LSD

DetectorEnergythreshold Estimated number of e A interaction e A interactionEstimatedEffectExp. N1N1N1N1 N2N2N2N2 N3N3N3N3 N4N4N4N4 LSD 5 – KII 7 – *2*2*2* BUST ~1 1** * De Rujula, 1987 ** Alexeyev, 1987

AMANDA Baikal LVD KGF KamLAND SK IMB SNO SOUD Arteomovsk LSD Baksan AMANDA NEUTRINO DETECTORS

SUPER K LVD SuperK LVD KamLand SNO

Detector Depth m.w.e Mass, ktons Thre- shold, MeV Efficiency Number of events Back- ground s -1 Arteomovsk ASD Russia C n H 2n Baksan BUST Russia (0.2) C n H 2n (67) 1.4 (2.2) 2.8 (4.3) (0.033) KamLAND USA Japan C n H 2n ~ Gran Sasso LVD Italy, Russia Fe 1.1 C n H 2n 4 – < 0.1 Kamioka Super-K Japan, USA H 2 O SNO Canada H 2 O 1 D 2 O

Radon peaks distribution vs time (November – March, 1997) The counting rate of the LVD during the earthquake in Italy, Arrows mark the moments of seismic shocks.

Neutrons generated by muons underground μs Number of Events

Reactions for scintillation and Cherenkov counters cm 2 MeV

The simplest case Double neutron star (NS) Almost all of the angular momentum can turn into an orbital angular momentum, J оrb ≤J o,  J= J o -J оrb 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 The only reaction of URCA-processes : Neutrino radiation luminosity per gramm (Ivanova et al, 1969; Imshennik, Nadyozhin, 1971, 1972)

 X max (  ) Y(  ) Central parameter of rotating collapsar (t ~ 2.5 sec) 2. Total energy of neutrino radiation (t ~ 6 sec) (Imshennik, Nadyozhin, 1977, 1992):

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]