The gravitational collapse of iron-oxygen stars with masses of 2M ⊙ and 10M ⊙ II

The collapse of iron-oxygen stars with masses of 2M has been calculated. The commencement of the collapse is due to dissociation of iron-group nuclei into free nucleons. After a while, the collapse proceeds in consequence of intensive energy losses due to neutrino volume radiation. At an intermediate stage of the collapse, the core — opaque with respect to neutrino radiation (neutrino core) — is formed inside the collapsing star. Both the gradual increase of the mass of the neutrino core and the partial absorption of neutrinos radiated from the surface of the neutrino core by the stellar envelope (deposition) were taken into account in our calculations. The kinetics of oxygen burning in the outer layers of the envelope was also allowed for. Neither the deposition, nor the oxygen burning, result in ejection of stellar envelopes.     

The collapse of iron-oxygen stars: Physical and mathematical formulation of the problem and computational method

A statement of the problem of gravitational collapse and a computational method are described. The main feature of the collapse — its extremely high heterogeneity — is taken into account. The structure of a collapsing star is characterized by a dense and hot nucleon core which is opaque with respect to neutrino radiation and is embedded in to and extended envelope, almost transparent to neutrinos. The envelope is gradually being accreted onto the core. The enormous amount of energy, radiated in the form of neutrinos and antineutrinos, make us pay particular attention to relatively small absorption of neutrino radiation by extended envelope (so-called energy of deposition). The inclusion of the energy deposition in the calculations is of importance for the problem of transformation of an implosion into an explosion. The deposition is taken into consideration in the approximation of diluted neutrino radiation which escapes from neutrino photosphere and is partially absorbed in the envelope. Both the generation of energy due to deposition and the change of neutronto-proton ratio are taken into account. The increase of the mass of the core, which is opaque with respect to neutrino radiation, is fully taken into account in the calculations of the gravitational collapse.     

The neutrino radiation for a hot neutron star formation and the envelope outburst problem

With the equations of neutrino heat conductivity being used, the neutrino light curve is calculated for the spherically symmetrical collapse of an iron-oxygen 2M star (Figure 1) up to the formation of a hot hydrostatically equilibrium neutron star. The total energy, radiated in the form of muon and electron neutrinos, is 5.8×10⁵³ erg (0.16Mc ²). The mean neutrino particle energy is 12 MeV for all the time the collapse proceeds. The maximum neutrino luminosity value is equal to 3×10⁵³ erg s^–1. For a 10M star collapse, the luminosity maximum 3×10⁵⁴ erg s^–1 takes place just at the moment of the formation of a black hole inside the collapsing star. The total radiated energy in this case is about 0.08Mc ². The set of calculations, allowing for the deposition of momentum by means of neutrino-nuclear coherent scattering, brings us to a conclusion that the envelope outburst is only possible if the scattering cross-section is 50 times larger than the value experimentally accepted (inequality 20)).     

A new representation of theH-functions of radiative transfer

The energetics involved in the formation of neutron stars in close binaries as a result of supernova explosions are considered. The gravitational binding energy of the neutron star must find proper outlets. The mass ejection and cosmic ray particles can carry away only a small fraction (up to a few per cent) of this energy. Most of the binding energy goes into rotational kinetic energy, gravitational radiation and neutrino emissions. A scenario is considered in which most of the gravitational binding energy goes into rotational kinetic energy and is, ultimately, radiated away as gravitational waves.     

LS I +61 303 as a potential neutrino source on the light of magic results

Very high energy γ-rays have recently been detected from the microquasar LS I +61 303 using the MAGIC telescope. A phenomenological study on the concomitant neutrinos that would be radiated if the γ-ray emission is hadronic in origin is herein presented. Neutrino oscillations are considered, and the expected number of events in a km-scale detector such as ICECUBE is computed under different assumptions including orbital periodicity and modulation, as well as different precision in the modeling of the detector. We argue that the upper limits already imposed on the neutrino emission of LS I +61 303 using AMANDA-II and the forthcoming measurements by ICECUBE may significantly constrain – in an independent and unbiased way – the γ-ray to neutrino flux ratio, and thus the possibility of a hadronic origin of the γ-rays. The viability of hadronic models based on wind–jet interactions in the LS +61 303 system after MAGIC measurements is discussed.     

Stopping power of matter and energy losses of solar neutrinos

The effects of neutrino mass and oscillations are investigated in the calculations of energy losses of solar neutrinos. In these calculations, we take into account the full energy dependence of the stopping power of matter for neutrinos. The case of Majorana neutrinos are also investigated. It is found that the total losses of energy of solar neutrinos are too small to account for the solar neutrino problem.     

Possible indication for non-zero neutrino mass and additional neutrino species from cosmological observations

The constraints on total neutrino mass and effective number of neutrino species based on CMB anisotropy power spectrum, Hubble constant, baryon acoustic oscillations and galaxy cluster mass function data are presented. It is shown that discrepancies between various cosmological data in Hubble constant and density fluctuation amplitude, measured in standard ΛCDM cosmological model, can be eliminated if more than standard effective number of neutrino species and non-zero total neutrino mass are considered. This extension of ΛCDM model appears to be ≈3σ significant when all cosmological data are used. The model with approximately one additional neutrino type, N _eff ≈ 4, and with non-zero total neutrino mass, Σmν ≈ 0.5 eV, provide the best fit to the data. In the model with only one massive neutrino the upper limits on neutrino mass are slightly relaxed. It is shown that these deviations from ΛCDM model appearmainly due to the usage of recent data on the observations of baryon acoustic oscillations. The larger than standard number of neutrino species is measured mainly due to the comparison of the BAO data with direct measurements of Hubble constant, which was already noticed earlier. As it is shown below, the data on galaxy cluster mass function in this case give the measurement of non-zero neutrino mass.     

Evidence for solar neutrino flux variability and its implications

Although KamLAND apparently rules out resonant-spin-flavor-precession (RSFP) as an explanation of the solar neutrino deficit, the solar neutrino fluxes in the Cl and Ga experiments appear to vary with solar rotation. Added to this evidence, summarized here, a power spectrum analysis of the Super-Kamiokande data reveals significant variation in the flux matching a dominant rotation rate observed in the solar magnetic field in the same time period. Three frequency peaks, all related to this rotation rate, can be explained quantitatively. A Super-Kamiokande paper reported no time variation of the flux, but showed the same peaks, there interpreted as statistically insignificant, due to an inappropriate analysis. This modulation is small (7%) in the Super-Kamiokande energy region (and below the sensitivity of the Super-Kamiokande analysis) and is consistent with RSFP as a subdominant neutrino process in the convection zone. The data display effects that correspond to solar-cycle changes in the magnetic field, typical of the convection zone. This subdominant process requires new physics: a large neutrino transition magnetic moment and a light sterile neutrino, since an effect of this amplitude occurring in the convection zone cannot be achieved with the three known neutrinos. It does, however, resolve current problems in providing fits to all experimental estimates of the mean neutrino flux, and is compatible with the extensive evidence for solar neutrino flux variability.     

Evidence for solar neutrino flux variability and its implications

Although KamLAND apparently rules out resonant-spin-flavor-precession (RSFP) as an explanation of the solar neutrino deficit, the solar neutrino fluxes in the Cl and Ga experiments appear to vary with solar rotation. Added to this evidence, summarized here, a power spectrum analysis of the Super-Kamiokande data reveals significant variation in the flux matching a dominant rotation rate observed in the solar magnetic field in the same time period. Three frequency peaks, all related to this rotation rate, can be explained quantitatively. A Super-Kamiokande paper reported no time variation of the flux, but showed the same peaks, there interpreted as statistically insignificant, due to an inappropriate analysis. This modulation is small (7%) in the Super-Kamiokande energy region (and below the sensitivity of the Super-Kamiokande analysis) and is consistent with RSFP as a subdominant neutrino process in the convection zone. The data display effects that correspond to solar-cycle changes in the magnetic field, typical of the convection zone. This subdominant process requires new physics: a large neutrino transition magnetic moment and a light sterile neutrino, since an effect of this amplitude occurring in the convection zone cannot be achieved with the three known neutrinos. It does, however, resolve current problems in providing fits to all experimental estimates of the mean neutrino flux, and is compatible with the extensive evidence for solar neutrino flux variability.     

Is an 11 eV sterile neutrino consistent with clusters, the cosmic microwave background and modified Newtonian dynamics?

In this paper, we show that if a single sterile neutrino exists such that     , it can serendipitously solve all outstanding issues of the Modified Newtonian Dynamics. We focus on fitting the angular power spectrum of the cosmic microwave background (CMB) in detail which is possible using a flat Universe with     and the usual baryonic and dark energy components. One cannot match the CMB if there is more than one massive sterile neutrino, nor with three active neutrinos of 2 eV. This model has the same expansion history as the Λ cold dark matter  (ΛCDM)  model and only differs at the galactic scale, where the modified dynamics outperform  ΛCDM  comprehensively. We discuss how an 11 eV sterile neutrino can explain the dark matter of galaxy clusters without influencing individual galaxies and potentially match the matter power spectrum.     

A global analysis searching for neutrinos associated with black hole merger gravitational wave events

Several neutrino observatories have searched for coincident neutrino signals associated with gravitational waves induced by the merging of two black holes. No statistically significant neutrino signal in excess of the background level was observed. These experiments use different neutrino detection technologies and are sensitive to various neutrino types. A combined analysis was performed on the KamLAND, Super-Kamiokande and Borexino experimental data with a frequentist statistical approach to achieve a global picture of the associated neutrino fluence. Both monochromatic and Fermi-Dirac neutrino spectra were assumed in the calculation. The final results are consistent with null neutrino signals associated with the process of a binary black hole merger. The derived 90% confidence level upper limits on the fluence and luminosity of various neutrino types are presented for neutrino energy less than110 MeV.     

Effect of Coulomb collisions on time variations of the solar neutrino flux

We consider the processes that might suppress the time variations in the solar neutrino flux produced by the radial motion of the Earth through the neutrino interference pattern. We calculate these time variations and the extent to which they are suppressed by Coulomb collisions of the neutrino-emitting nuclei. This is done for both the 0.862-MeV ⁷Be neutrino line and the continuous neutrino spectrum, assuming a Gaussian energy response function of the neutrino detector. We find that the collisional decoherence averages out the time variations for neutrino masses A simple and clear physical picture of the time-dependent solar neutrino problem is presented and qualitative coherence criteria are discussed.     

Neutron star electrodynamics in curved space

We calculate the fields surrounding and the power radiated by a slowly rotating neutron star with a frozen-in magnetic dipole field, tilted with respect to the rotation axis, including the effects of spacetime curvature. The general relativistic effects suppress the radiated power relative to flat space by factors up to 1/7 for magnetic dipole radiation and 1/50 for the associated electric quadrupole radiation. This suppression exceeds that which might be expected from a surface red shift alone.Numerical results are found using power series which describe the behavior of electromagnetic fields exterior to a black hole or slowly rotating neutron star. These new solutions, appropriate near the stellar surface, converge for all radii exterior to the neutron star (or black hole) making analytic continuation of the power series unnecessary as well as allowing matching to a linear combination of asymptotic expansions, appropriate for large radius. Typical numerical values for these functions are presented as well as techniques for accelerating the convergence of their respective power series which make them attractive alternatives to numerical integration.Supported in part by NSF Grant PHY 77 28356.     

Radiation from a dipole in an anisotropic plasma medium containing time-varying irregularities

The expression for power radiated from a dipole within an anisotropic plasma has been obtained in presence of a current source and time-varying irregularities. This may be useful for numerical computation in lossy media.     

A heuristic remark on the periodic variation in the number of solar neutrinos detected on Earth

Four operating neutrino observatories confirm the long standing discrepancy between detected and predicted solar neutrino flux. Among these four experiments the Homestake experiment is taking data for almost 25 years. The reliability of the radiochemical method for detecting solar neutrinos has been tested recently by the GALLEX experiment. All efforts to solve the solar neutrino problem by improving solar, nuclear, and neutrino physics have failed so far. This may also mean that the average solar neutrino flux extracted from the four experiments may not be the proper quantity to explain the production of neutrinos in the deep interior of the Sun. Occasionally it has been emphasized that the solar neutrino flux may vary over time. In this paper we do address relations among specific neutrino fluxes produced in the proton-proton chain that are imposed by the coupled systems of nonlinear partial differential equations of solar structure and kinetic equations by focusing our attention on a statistical interpretation of selected kinetic equations of PPII/PPIII branch reactions of the protonproton chain. A fresh look at the statistical implications for the outcome of kinetic equations for nuclear reactions may shed light on recent claims that the⁷ Be-neutrino flux of the Sun is suppressed in comparison to the pp- and⁸B neutrino fluxes and may hint at that the solar neutrino flux is indeed varying over time as shown by the Homestake experiment.     

Neutrino chemical potential and neutrino heat conductivity with allowance for neutrino scattering

The equations of neutrino hydrodynamics are derived in two different approximations taking into consideration the neutrino scattering from stellar material. In a thermal-conductivity approximation which holds good when neutrino optical depth with respect to absorption exceeds 1, the neutrino scattering is taken into account, analogously with photon radiative conductivity, by introducing the transport cross-section in the neutrino mean free path. In a practically important case when the neutrino optical thickness with respect to scattering is high enough, whereas that concerning absorption is sufficiently low, another approximation of Comptonized neutrinos is valid. In this case, the neutrino and antineutrino chemical potentials are independent of each other. They have to be calculated from equations of continuity established for neutrino and antineutrino alongside with the diffusion equation expressing the law of lepton-charge conservation. The equations of neutrino hydrodynamics are written out both with and without inclusion of muon neutrinos and antineutrinos.The equations obtained are established to deal properly with neutrino diffusion inside collapsing stars.     

Schwarzschild electrodynamics: Black holes,neutron stars

We present a number of calculations involving the production and propagation of electromagnetic waves in the Schwarzschild metric. They are based on algorithms developed from the power series solutions of the Schwarzschild radial equation (Regge-Wheeler equation) of Arenstorf, Cohen and Kegeles. These include the scattering of electromagnetic plane waves from a Schwarzschild black hole where we find that previous approximate and numerical work is correct and extend those results to higher frequencies and multipolarities. Exact results for the absorption cross-section are presented. We calculate the power radiated from a radially vibrating neutron star and find that the radiation can be hyperemissive. For example, we find for a surface radius of 1.8 Schwarzschild radii the power radiated is enhanced by as much as factor of 3.7, 4.1, 5.1, for dipole, quadrupole and octupole radiation respectively, making electromagnetic radiation a more effective damping mechanism than in flat space. The Schwarzschild radial functions are extensively treated in the appendices and numerical results are presented for various frequencies and radii. A simple asymptotic expansion for one of the connection constants, appropriate for high frequency, is also given.Supported in part by NSF Grant PHY 77-28356.     

The approximation of neutrino heat conduction with neutrino scattering

We have developed an algorithm for taking into account the neutrino scattering in the approximation of neutrino heat conduction. We show that in the case of incoherent neutrino scattering (e.g., by electrons), the coefficients of the temperature and chemical potential gradients are averaged over the neutrino energy using functions that can be found by numerically solving integral equations. The coherent scattering by free nucleons and atomic nuclei can be described by introducing a transport cross section. We suggest a new method for calculating the neutrino—electron scattering functions that is based on Fermi—Dirac functions of integer indices.     

Standard and Non-Standard Solar Models

We summarize the physical input and assumptions commonly adopted in modern standard solar models that also produce good agreement with solar oscillation frequencies. We discuss two motivations for considering non-standard models: the solar neutrino problem and surface lithium abundance problem. We begin to explore the potential for mixed core models to solve the neutrino problem, and compare the structure, neutrino flux, and oscillation frequency predictions for several models in which the inner 25% of the radius is homogenized, taking into account the effects of non-local equilibrium abundances of ³He. The results for the neutrino flux and helioseismic predictions are far from satisfactory, but such models have the potential to reduce the predicted ⁷Be/⁸B neutrino flux ratio, and further studies are warranted. Finally, we discuss how much the neutrino problem can be alleviated in the framework of the standard solar model by using reaction rates, abundances and neutrino capture cross-sections at the limits of their uncertainties, while still satisfying the constraints of helioseismology.     

On the long-period variations and magnitude of the solar neutrino flux

We analyze the solar neutrino flux fluctuations using data from the Homestake, GALLEX, GNO, SAGE, and Super Kamiokande experiments. Spectral analysis and direct quantitative estimations show that the quasi-five-year periodicity is the most stable neutrino flux variation. Revised mean solar neutrino fluxes are presented. These are used to estimate the observed pp flux of the solar electron neutrinos near the Earth. We consider two alternative explanations for the origin of the variable component of the solar neutrino deficit.