Supernova SN1987A Research Articles

Bayesian analysis of neutrinos observed from supernova SN 1987A

We present a Bayesian analysis of the energies and arrival times of the neutrinos from supernova SN 1987A detected by the Kamiokande II, IMB, and Baksan detectors, and find strong evidence for two components in the neutrino signal: a long time scale component from thermal Kelvin-Helmholtz cooling of the nascent neutron star, and a brief $(\ensuremath{\sim}1 \mathrm{s}),$ softer component similar to that expected from emission by accreting material in the delayed supernova scenario. In the context of this model, we show that the data constrain the electron antineutrino rest mass to be less than 5.7 eV with 95% probability. Our analysis takes advantage of significant advances that have occurred in the years since the detections in both our understanding of the supernova mechanism and our ability to analyze sparse data. This has led to significant improvement over previous studies in two important respects. First, our comparison of the data with parametrized models of the neutrino emission uses a consistent and straightforward Bayesian statistical methodology. This methodology helps us distinguish the complementary tasks of parameter estimation and model assessment, and fully accounts for the strong, nonlinear correlations between inferred values of neutrino emission model parameters. It also clarifies and improves the derivation of the likelihood function (the probability for the data), improving on earlier derivations in two ways: more consistent accounting for the energy-dependent efficiencies of the detectors; and inclusion of the empirically measured detector background spectra. These improvements lead to significant differences between our inferences and those found in earlier studies. Inclusion of detector background spectra proves crucial for proper analysis of the Baksan data and for demonstrating its consistency with data from other detectors. Second, we compare the data with a much wider variety of neutrino emission models than was explored previously, several of them inspired by recent numerical calculations of collapse and explosion based on the delayed supernova mechanism. This allows us to compare predictions of both the prompt and delayed mechanisms with the data, and ensures that our conclusions are robust. We find that two-component models for the neutrino signal are $\ensuremath{\sim}100$ times more probable than single-component models. Moreover, single-component models imply a radius and binding energy for the nascent neutron star significantly larger than those implied by even the stiffest acceptable equations of state for neutron star matter. In contrast, the radius and binding energy implied by two-component models are in agreement with predictions. Taking this agreement with prior expectations into account increases the odds in favor of two-component models by more than an order of magnitude. The inferred characteristics of the neutrino emission are in spectacular agreement with the salient features of the theory of stellar collapse and neutron star formation that had developed over several decades in the absence of direct observational data. We compare our work with previous work that used more conventional ``frequentist'' methods (including our own previous maximum likelihood analysis). We identify several methodological and technical weaknesses in earlier analyses, and show how these are overcome in our Bayesian analysis.

SN 1987A Revisited as a Major Production Site for [CLC][ITAL]r[/ITAL][/CLC]-Process Elements

The origin of nucleosynthesis products of rapid neutron capture reactions (the r-process) is a long-standing astrophysical problem. Recent analyses of elemental abundances for extremely metal-poor stars shed light on the elemental abundances of individual supernovae. Comparison of the abundance distributions of some extremely metal-poor stars with those of the best-observed supernova SN 1987A clearly indicates that the overabundances of barium and strontium found in SN 1987A that have been ascribed to the slow neutron capture process must be results of r-process nucleosynthesis. The mass of freshly synthesized barium in SN 1987A is estimated to be 6 × 10-6 M☉ based on the observed surface abundance and detailed hydrodynamical models for this supernova. These new findings lead to the conclusion that 20 M☉ stars, one of which is the progenitor star of SN 1987A, are the predominant production sites for r-process elements in the Galaxy and the r-process element donors for notable neutron capture-rich giant stars, CS 22892-052 and CS 31082-001.

How a quark–gluon plasma phase modifies the bounds on extra dimensions from SN1987a

The shape of the neutrino pulse from the supernova SN1987a provides one of the most stringent constraints on the size of large, compact, “gravity-only” extra dimensions. Previously, calculations have been carried out for a newly-born proto-neutron star with a temperature of about 50 MeV at nuclear matter density. It is arguable that, due to the extreme conditions in the interior of the star, matter might be a quark–gluon plasma, where the relevant degrees of freedom are quarks and gluons rather than nucleons. We consider an energy-loss scenario where seconds after rebounce the core of the star consists of a hot and dense quark–gluon plasma. Adopting a simplified model of the plasma we derive the necessary energy-loss formulae in the soft-radiation limit. The emissivity is found to be comparable to the one for nuclear matter and bounds on the radius of extra dimensions are similar to those found previously from nuclear matter calculations.

Large lepton mixing and supernova 1987A

We reconsider the impact of $\bar\nu_e \leftrightarrow \bar\nu_{\mu,\tau}$ neutrino oscillations on the observed $\bar\nu_e$ signal of supernova SN 1987A. Performing a maximum-likelihood analysis using as fit parameters the released binding energy $\Eb$ and the average neutrino energy $\Ee$, we find as previous analyses that $\bar\nu_e \leftrightarrow \bar\nu_{\mu,\tau}$ oscillations with large mixing angles have lower best-fit values for $\Ee$ than small-mixing angle (SMA) oscillations. Moreover, the inferred value of $\Ee$ is already in the SMA case lower than those found in simulations. This apparent conflict has been interpreted as evidence against the large mixing oscillation solutions to the solar neutrino problem. In order to quantify the degree to which the experimental data favour the SMA over the large mixing solutions we use their likelihood ratios as well as a Kolmogorov-Smirnov test. We find within the range of SN parameters predicted by simulations regions in which the LMA-MSW solution is either only marginally disfavoured or favoured compared to the SMA-MSW solution. We conclude therefore that the LMA-MSW solution is not in conflict with the current understanding of SN physics. In contrast, the vacuum oscillation and the LOW solutions to the solar neutrino problem can be excluded at the $4\sigma$ level for most of the SN parameter ranges found in simulations. Only a marginal region with low values of $\Ee$, $<E_{\bar\nu_{\mu,\tau}}>$ and $\Eb$ is left over, in which these oscillation solutions can be reconciled with the neutrino signal of SN 1987A.

An introduction to the spectroscopy of H3+

The infrared spectra of H3+ and D3 were first observed almost simultaneously in 1980. Since then there has been extensive laboratory work on H3 and its D-isotopomers. In addition, the spectrum of H3+ has been observed in emission from the atmospheres of the giant planets Jupiter, Saturn and Uranus, and probably from the supernova SN1987A, and recently in absorption in interstellar clouds. In this introductory paper, the assignment of the spectra and some of the characteristic features associated with the strong anharmonicity are discussed. As the convergence of the perturbation series is poor, the large centrifugal effects are best calculated in a variational type of approach, where the rotational energy in the Hamiltonian can be treated essentially exactly. Ab initio calculations have steadily improved over the years, and recent work has given completely theoretical vibration–rotation term values for the low vibrational states with an accuracy better than 0.1 cm-1 in almost all cases, adequate for most spectroscopic assignment purposes.

Dissociative Charge Transfer between Ground‐State He+and CO at Electron‐Volt Energies

The major mechanism for the destruction of CO in the ejecta of the supernova SN 1987A has been assumed to be the fast dissociative charge transfer reaction of He+(1s) + CO → products. However, no direct experimental data were available to confirm this hypothesis. In this measurement, we used the ion storage technique to measure the rate coefficient of this reaction within the temperature range of the ejecta. The measured rate coefficients are 1.33(±0.15) × 10-9, 1.48(±0.15) × 10-9, and 1.44(±0.12) × 10-9 cm3 s-1 at 2.9 × 103, 8.7 × 103, and 1.2 × 104 K, respectively. The measured rate coefficients do not appear to be temperature dependent within this temperature range. Our measured value is consistent with the value used in the chemical modeling of the supernova SN 1987A ejecta.

Axion searches

The strong CP problem and its resolution through the existence of an axion are briefly reviewed. The constraints on the axion from accelerator searches, from the evolution of red giants and from supernova SN1987a combine to require m a < 3 · 10 −3 eV, where m a is the axion mass. On the other hand, the constraint that axions do not overclose the universe implies m a ≳ 10 −6 eV. If m a ∼ 10 −5 eV, axions contribute significantly to the cosmological energy density in the form of cold dark matter. Dark matter axions can be detected by resonant conversion to microwave photons in a cavity permeated by a static magnetic field and tuned to the axion mass. Experiments using this effect are described, as well as several other types of axion searches.

Carbon Monoxide Formation in SN 1987A

The formation of carbon monoxide in the supernova SN 1987A at 200 days is investigated. Rather than the one-zone that have previous been employed, this work utilizes a radially dependent radiative transport model to compute the temperature and ionization structure and the destruction of CO and CO+ by ultraviolet radiation. The CO profile is computed assuming chemical equilibrium. Two models for the density and abundance profiles are examined: model 10H (unmixed) and model 10HMM (mixed) of Pinto & Woosley. Sensitivity to adopted rates and temperature as it might be affected by CO cooling is examined. The models give a total mass of 10-4 M_sun at 200 days for the unmixed model, which is comparable with the estimated observed abundance by Syromilio et al. but nearly 2 orders of magnitude less than the estimated observed and that computed in thermal-chemical models by Liu & Dalgarno. The effect of different model assumptions and results concerning ionization structure and radiative transfer are discussed. We confirm that CO+ is not expected to be produced in significant amounts and that the amount of CO is sensitive to the degree of the mixing of the composition of various elements present in the ejecta.

Neutrinos in cosmology

About neutrinos, we only know that the three left handed \(\nu_{\rm e_{\rm{L}}} , \nu_{\mu_{\rm{L}}} , \nu_\tau\) exist, that they have weak interactions and that they are much lighter than their corresponding charged leptons. They may be massive or massless, stable or not. If they are massive, they may be the left-handed part of the Majorana or Dirac fermions. If neutrinos are Majorana fermions, the right-handed neutrinos νR may or may not exist and may be heavy or light. If neutrinos are Dirac fermions, the νR must exist. Neutrinos may have new interactions, other than weak, which may allow them to annihilate or decay faster. Not just laboratory experiments can investigate these possibilities: because neutrinos were present in large numbers in the early universe, their properties affect the evolution and the present structure of the universe. Our knowledge of the history of the universe is thus used as a laboratory for placing limits on the mass, lifetime and number of flavours of neutrinos. Also astrophysics leads to limits on neutrinos, the recent observations of neutrinos from the supernova SN 1987A being an outstanding example. On the other hand, the knowledge of some properties of neutrinos may be crucial for cosmology and astrophysics. For example, the solution to a major cosmological problem would be given by a neutrino mass of around 30eV. This would mean that the “dark matter” consists of light neutrinos.

Kamiokande and Super-Kamiokande

Neutrino astrophysics has begun in 1987 when Kamiokande observed the neutrino burst from a supernova SN1987A. Kamiokande succeeded to observe solar neutrinos and demonstrated at the first time that the observed neutrinos are comig from the direction of the sun and confirmed the long standing solar neutrino problem. The atmospheric neutrino anomaly was first pointed out by the Kamiokande experiment in 1988 and is now thought to be an evidence of a neutrino oscillation. Super-Kamiokande, the bigger successor of Kamiokande, started its operation in April 1996. The accumulated data have already exceeded those of Kamiokande in its quality and quantity. New insights into neutrino masses will be obtained from the results of SK in very near future.

Signals from SN 1987A in Amaldi-Weber antennas as the possible detection of scalar gravitational waves

An equation is obtained for the cross section of a metal Weber cylinder for scalar gravitational waves, which are possible within the framework of the field theory of gravitation. It is shown that the signals detected by the Amaldi and Weber antennas during the explosion of supernova SN 1987A can be interpreted as the result of the action of scalar gravitational waves on solid-state detectors. The required energy of the gravitational waves is about 1 M⊙c2. Together with the observed excess (about 1 %) of gravitational radiation from the binary system containing the pulsar PSR 1913+16, the signals from SN 1987A are the second piece of observational evidence for the actual existence of scalar gravitational waves. The present-day, third-generation, solid-state antennas are capable of detecting scalar waves from events like SN 1987A at a distance up to 5 Mpc. The expected level of the signal from SN 19931 is about 7 mK. An experimental test of the longitudinal nature of scalar waves is possible using interferometric antennas based on free masses.

Type II Supernovae SN 1987A and SN 1993J

The optical and ultraviolet emission from the type II supernova SN 1987A is currently powered by the radioactive decay of titanium-44. In contrast, the emission from SN 1993J is dominated by radiation from the interaction of the supernova shock wave with a dense, stellar wind released before the explosion. The dense wind around SN 1987A was displaced by the fast wind from the compact progenitor star, and the interaction of the supernova with dense gas is now being detected at x-ray and radio wavelengths. The expected neutron stars or black holes at the centers of these supernovae are not yet significant power sources.

Molecules and Dust in Supernovae

Observations of molecules and dust in supernova SN 1987a and SN 1995ad are summarised and the inferred masses of CO and SiO are presented. The chemistry is used to argue that macroscopic mixing occurred in which the interpenetrating clumps in the ejecta retained their microscopic integrity. An explanation of the anomalous temperature structure is advanced. Molecular candidates for some of the unidentified spectral features are proposed.

Formation of the SN1987A Ring due to magnetic pressure

Several weeks after the explosion of supernova (SN) SN1987A, the UV flash of the SN illuminated a ring-like structure in the circumstellar material at about 0.65 ly from the SN. The interaction between the stellar winds from the SN progenitor is considered to be the candidate for the formation of the circumstellar structure. In the case that the stellar winds are spherically symmetric, the interaction should result in a shell-like structure. However, Washimi, Shibata &amp; Mori (1996) show that the magnetic field in the winds causes an anisotropy which leads to the formation of a ring-like structure. When the fast wind of the blue supergiant phase of the progenitor sweeps up the surrounding slow wind of the red-supergiant phase, the magnetic field as well as the wind material are piled up in the interaction region. Since the magnetic energy increases in proportion to the square of the amplitude, the magnetic field exhibits its effect prominently at the interaction region; due to the magnetic pressure force the material at lower latitudes is compressed into a ring-like structure. It is suggested that this magnetic process can also explain the newly observed pair of rings of the SN1987A nebula. We note that the idea of a magnetic field effect is consistent with the radio observation of a supernova remnant, detected by Staveley-Smith et al. (1992) at about 1200 days after the explosion. This radio emission is explained by the collision of the supernova blast wave with the shocked blue wind. This position corresponds to the averaged expansion speed of the supernova ejecta ∼ 0.08 ly which is consistent with the estimation by Shigeyama and Nomoto (1990). The estimated magnetic-energy density by the minimum-energy argument is ∼ 4 × 10–8f–4/7N m–2, where f is the fractional volume of the radiating acceleration region, suggesting a magnetic field of a few milli-Gauss or more (Chevalier 1992). This field intensity is consistent with an intensity of ≈ 2 · 10–4 Gauss obtained between the reverse shock and the contact surface shown, if one takes into account a further enhancement of the field due to the sweeping-up process by the supernova blast wave. When the SN ejector collides with the ring at the end of this century or at the beginning of the next one, we can also expect more intense radio emission at rather middle and high latitudes where the magnetic intensity is greater, rather than at the equator where the ring-like structure is located.

Strangeness in stellar matter

A protoneutron star is formed immediately after the gravitational collapse of the core of a massive star. At birth, the hot and high density matter in such a star contains a large number of neutrinos trapped during collapse. Trapped neutrinos generally inhibit the presence of exotic matter -- hyperons, a kaon condensate, or quarks. However, as the neutrinos diffuse out in about 10-15 s, the threshold for the appearance of strangeness is reduced; hence, the composition and the structure of the star can change significantly. The effect of exotic, negatively-charged, strangeness-bearing components is always to soften the equation of state, and the possibility exists that the star collapses to a black hole at this time. This could explain why no neutron star has yet been seen in the remnant of supernova SN1987A, even though one certainly existed when neutrinos were detected on Feb. 23, 1987. With new generation neutrino detectors it is feasible to test different theoretical scenarios observationally.

Radio Observations of SN 1987A at 843 MHz

view Abstract Citations (30) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radio Observations of SN 1987A at 843 MHz Ball, Lewis ; Campbell-Wilson, D. ; Crawford, D. F. ; Turtle, A. J. Abstract We report here the entire history to date of the radio observations of SN 1987A at 843 MHz. These data provide the most comprehensive time sampling of the radio emission from this unique source. Two phases of radio emission from supernova SN 1987A in the Large Magellanic Cloud have been detected with the Molonglo Observatory Synthesis Telescope (MOST) at 843 MHz. At the time of the first observations on 1987 February 25, 2 days after the explosion, the first phase had already begun. The radio flux density peaked within the next 2 days and then decayed monotonically. The flux density dropped below the 3 σ detectability limit ∼200 days after the explosion, although the decreasing trend suggests that the emission persisted somewhat longer. In 1990 June, around day 1200, it became apparent that SN 1987A had reappeared at 843 MHz. Later analysis revealed that the onset of this second phase of radio emission occurred considerably earlier. Since then the radio flux density has increased monotonically, and regular observations of SN 1987A with the MOST are continuing. Publication: The Astrophysical Journal Pub Date: November 1995 DOI: 10.1086/176446 Bibcode: 1995ApJ...453..864B Keywords: RADIO CONTINUUM: STARS; STARS: SUPERNOVAE: INDIVIDUAL ALPHANUMERIC: SN 1987A full text sources ADS | data products SIMBAD (5) NED (2)

AN ALGORITHM FOR A PERIOD SEARCH IN A SPARSELY COVERED TIME SERIES AT A FIXED PHASE

Abstract. Researchers are sometimes faced with a set of observations that constitute a sparse coverage of a time series, suspected to be periodic. The period is unknown, but one can identify in the observed data a few points that are presumed to occur at the same phase, in different cycles of the unknown periodicity. We propose an algorithm that finds all periods which are compatible with such observed data, and suggest how to assess their statistical significance. The algorithm also provides stringent limits on the epochs of the fixed phase. We give three examples, from the field of astronomy, for application of our new algorithm. In the first one the algorithm reveals, on the basis of very few photometric observations, a highly significant period in the light curve of the recent classical Nova Herculis 1991. In the second example, in the series of arrival times of neutrinos from the supernova SN1987A, our algorithm yields a definite negative result. It proves that no significant exact periodicity is present in the data. In the third application, the algorithm provides new constraints on the epoch of one of the minima in the light curve of the stellar binary system 44i Bootis. We compare the method with other period search techniques, pointing out a few of its advantages, as well as some of its weaknesses.

Iron whiskers in supernova SN 1987A

The far-infrared flux measurements for supernova SN 1987A are modelled in terms of length distributions of iron whiskers. The excess emission detected at ⋋ ≡ 1.3µm can be explained on the basis of such a model.

What astronomy has learned from observations of

We review the uses to which [Formula: see text] astronomical observations have been put, in the five years since the first detection of this molecular ion in the aurorae of Jupiter. Spectroscopy of Jupiter shows that the ionospheric temperature is high (~1000 K) compared with the lower atmosphere and that auroral column densities are between 1012 and 1013 cm−2. The molecule is also distributed widely across the planet in concentrations about 10% of peak auroral densities. Imaging in [Formula: see text]-sensitive wavelengths links the aurorae to open magnetic field lines, rather than those encompassing the Io plasma torus. Uranus shows [Formula: see text] emission intensities of a few percent of the peak jovian auroral lines, with somewhat weaker emission from Saturn. On Uranus, [Formula: see text] is distributed fairly evenly across the planet, with some indication that auroral enhancement is not more than a factor of two. Saturnine [Formula: see text] appears to be concentrated more towards the magnetic poles. The identification of [Formula: see text] in the spectrum of the type II supernova SN1987a constrains models of the explosion to avoid microscopic mixing during much of the first year of the event. So far no reliable detection of [Formula: see text] in the interstellar medium has been reported.

NEUTRINOS FROM SUPERNOVAE

The historic detection of neutrinos from supernova SN1987A demonstrated that they are an invaluable source of information about neutrino properties and the dynamics of gravitational stellar collapse. A number of experiments are currently being prepared for the next detection of the supernova neutrino burst. This article reviews the data of SN1987A, the puzzles they presented and the lessons about neutrino properties that they provided. A special emphasis is put on the preparation for future detections and evaluation of an improvement in understanding basic neutrino properties that can be achieved.