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NASA NTRS1987

When will a pulsar in supernova 1987a be seen?

The means by which a pulsar might be detected in the remnant of supernova 1987a in the Large Magellanic Cloud is examined. One possibility is that the slower-than-radioactive decay typically seen in the type II light curves is itself the sign of powering by the underlying pulsar, with the decline representing not the spinning down of the pulsar but rather the declining nebular opacity that would allow increasing amounts of the energy to escape as gamma rays. The test of this hypothesis (if the supernova conforms to type II expectations) would be to look for the 'missing' energy in the form of those gamma rays that escape from the remnant instead of powering it.

Michel, F. Curtis↗

NASA NTRS1987

Light echoes - Supernovae 1987A and 1986G

The sudden brilliance of a supernova (SN) eruption will be reflected on surrounding dust grains to create a phantom nebula. The paper presents a series of calculations in which the apparent brightness of this 'light echo' is predicted for a variety of situations where the dust is part of the interstellar medium (ISM). It is found that the supernova 1987 A will have a very bright echo off the ISM that may perhaps be visible with binoculars for many years. At a time of 400 days past maximum, the SN 1986G is found to be 2.7 mag brighter than would be predicted by an extrapolation of its light curve. This unique property has an easy explanation as a light echo off the dust in the dust lane of Cen A.

Schaefer, Bradley E.↗

NASA NTRS1988

A mechanism for strong shock electron heating in supernova remnants

It is shown that collisionless shock waves propagating away from a supernova may be directly responsible for the 10 keV X-ray emission seen in supernova remnants. A sequence of plasma instabilities (Buneman and ion acoustic) between the reflected and/or transmitted ions and the background electrons at the foot of the shock front can give rise to rapid anomalous heating of electrons. Hybrid simulations of a perpendicular collisionless shock are presented to demonstrate that this heating can arise within a self-consistently computed shock structure.

Cargill, P. J.↗

NASA NTRS1988

Observations of supernova SN1987a

Supernova SN1987a was discovered on February 23, 1987, in the Large Magellanic Cloud, a nearby galaxy that is visible only from the Southern Hemisphere. The NASA program for observations of SN1987a, which was developed rapidly after the discovery of the explosion, was designed to be implemented through a series of coordinated campaigns of gamma-ray, X-ray, ultraviolet, and infrared observations from spacecraft, rockets, balloons, aircraft and the ground. The author summarizes models for supernovae, recent results for SN1987a, and the NASA plans for further observations.

Riegler, Guenter R.↗

NASA NTRS1988

The influence of supernovae and passing stars on comets in the Oort cloud

It is demonstrated here that the passage of luminous stars through the Oort Cloud over the age of the solar system will subject all comets to heating episodes up to at least 16 K, and a sizeable fraction to 30 K. Stochastic supernovae have even more striking effects during monthlong events; conservative estimates of the supernovae are in the Galactic disk suggest that most comets have been heated to 45 K, and a fraction to about 60 K. These results imply that comets are not fully pristine relics of solar system formation.

Stern, S. Alan↗

NASA NTRS1989

Computer simulations of cosmic-ray diffusion near supernova remnant shock waves

A plasma simulation model was used to study the resonant interactions between streaming cosmic-ray ions and a self-consistent spectrum of Alfven waves, such as might exist in the interstellar medium upstream of a supernova remnant shock wave. The computational model is a hybrid one, in which the background interstellar medium is an MHD fluid and the cosmic-rays are discrete kinetic particles. The particle sources for the electromagnetic fields are obtained by averaging over the fast cyclotron motions. When the perturbed magnetic field is larger than 10 percent of the background field, the macro- and microphysics are no longer correctly predicted by quasi-linear theory. The particles are trapped by the waves and show sharp jumps in their pitch-angles relative to the background magnetic field, and the effective ninety-degree scattering time for diffusion parallel to the background magnetic field is reduced to between 5 and 30 cyclotron periods. Simulation results suggest that Type 1 supernova remnants may be the principal sites of cosmic ray acceleration.

Max, C. E.↗

NASA NTRS1989

Are supernova remnants quasi-parallel or quasi-perpendicular accelerators

Observations of shock waves in the solar system which show a pronounced difference in the plasma wave and particle environment depending on whether the shock is propagating along or perpendicular to the interplanetary magnetic field are discussed. Theories for particle acceleration developed for quasi-parallel and quasi-perpendicular shocks, when extended to the interstellar medium suggest that the relativistic electrons in radio supernova remnants are accelerated by either the Q parallel or Q perpendicular mechanisms. A model for the galactic magnetic field and published maps of supernova remnants were used to search for a dependence of structure on the angle Phi. Results show no tendency for the remnants as a whole to favor the relationship expected for either mechanism, although individual sources resemble model remnants of one or the other acceleration process.

Spangler, S. R.↗

NASA NTRS1989

Pair production of helicity-flipped neutrinos in supernovae

The emissivity was calculated for the pair production of helicity-flipped neutrinos, in a way that can be used in supernova calculations. Also presented are simple estimates which show that such process can act as an efficient energy-loss mechanism in the shocked supernova core, and this fact is used to extract neutrino mass limits from SN 1987A neutrino observations.

Perez, Armando↗

NASA NTRS1988

Supernova remnants and the interstellar medium - Constraints from cosmic-ray acceleration

The reacceleration rate of cosmic rays by supernova (SN) remnants is calculated and expressed in terms of the parameters determining the cosmic ray model and the SN expansion. It is shown that the constraint on reacceleration derived from the B/C data leads to constraint on the expansion of SN remnants in the ISM and on the effective density of ISM. The effect of cloud evaporation is estimated and the expansion rate of supernova remnants, cosmic ray reacceleration, and the state of the ISM are solved for simultaneously. In the resulting self-consistent solution, SN remnants produce a reacceleration rate and an effective acceleration shock strength which is consistent with the values indicated by the cosmic ray data.

Wandel, A.↗

NASA NTRS1989

X-ray halos around supernova remnants

The results are reported of an Einstein Observatory imaging proportional counter investigation of the X-ray halos of the four brightest young Galactic supernova remnants: the Crab Nebula, Cas A, Tycho's, and Kepler's supernova remnant. It is found that the size, shape, and rough intensity of each of these sources are consistent with the measured properties of the X-ray halos of compact Galactic X-ray sources, and as such are consistent with an origin due solely to the scattering of X-rays by interstellar grains.

Mauche, Christopher W.↗

NASA NTRS1988

Infrared opportunities for supernova 1987A

IR observations of SN 1987A are reviewed, focusing on the IR processes in the supernova. IR line emission, IR emission from supernova condensates, IR echoes, IR emission from shock-heated dust, and IR emission from a cometary cloud are examined. A list is given of IR studies of SN 1987A and the characteristics of the instruments used in these studies. Preliminary results from several IR studies are considered.

Dwek, Eli↗

NASA NTRS1989

On evidence for quasi-parallel and quasi-perpendicular acceleration in supernova remnants

An attempt is made to determine whether or not the structure of supernova remnant shells is dependent on the angle between the line of sight and the Galactic magnetic field and if this structure can be explained either by quasi-parallel or quasi-perpendicular acceleration. The method used to determine the line of sight angles to the magnetic field is described. A model for the emissivity of a supernova remnant is developed.

Leckband, James A.↗

NASA NTRS1989

Does Supernova 1987A contain a rapidly vibrating neutron star?

If the recently reported 0.5 ms-period pulsed optical signal from the direction of Supernova 1987A originated in a young neutron star, its interpretation as a rotational period has difficulties. The surface magnetic field would have to be much lower than expected, and the high rotation rate may rule out preferred nuclear equations of state. It is pointed out here that a remnant radial vibration of a neutron star, excited in the supernova event, may survive for several years with about the observed (gravitationally redshifted) period. Heavy ions at the low-density stellar surface, periodically shocked by the vibration, may efficiently produce narrow pulses of optical cyclotron radiation in a surface field of about a trillion gauss.

Wang, Q.↗

NASA NTRS1989

The late behavior of supernova 1987A. I - The light curve. II - Gamma-ray transparency of the ejecta

Observations of the late (t = 20-1500 days) bolometric light curve and the gamma-lines and X-rays from supernova 1987A are compared to theoretical models. It is found that 0.073 + or - 0.015 solar masses of freshly synthesized Ni-56 must be present to fit the bolometric light curve. The results place limits on the luminosity and presumed period of the newly formed pulsar/neutron star. In the second half of the paper, the problem of computing the luminosities in gamma-ray lines and in X-rays from supernova 1987A is addressed. High-energy observations suggest the development of large-scale clumping and bubbling of radioactive material in the ejecta. A model is proposed with a hydrogen envelope mass of about 7 solar masses, homologous scale expansion velocities of about 3000 km/s, and an approximately uniform mass distribution.

Arnett, W. David↗

NASA NTRS1989

Mystery spot in supernova 1987A - Reflection or fluorescence by an interstellar cloud?

This paper explores fluorescence and reflection models of the companion to SN 1987A obseved by speckle interferometry, recalling a 1901 precedent. The apparent small angular size of the companion is a severe constraint. A fluorescence model cannot reach the observed brightness unless the ultraviolet burst from the supernova contained as many as 2 x 10 to the 58th ionizing photons. This is about 25 times stronger than generous current models. Even then, the expected line ratios and widths do not fit the observations. The absence of narrow H-alpha and H-beta lines in the supernova spectrum, the ratio of fluxes of the companion in H-alpha and forbidden N II line filters, the invisibility of the companion at 4861 (H-beta), and its detection at 5330 fail to agree with theory. A dust-reflection model is more promising, and the color can be reddened by the evaporation of small grains, but the model still falls more than about 1 mag short in brightness. Furthermore, a dust reflection should have increased in relative brightness in May-June 1987, rather than disappearing as the mystery spot did. If all the observations are correct, neither model is likely to work.

Felten, James E.↗

NASA NTRS1989

Radio emission from young supernova remnants - Effects of an inhomogeneous circumstellar medium

The evolution of young supernova remnants has been modeled using a one-dimensional hydrodynamics code. Rayleigh-Taylor instabilities and the growth of Rayleigh-Taylor fingers have been included in the code. Turbulent dynamo amplification of magnetic fields and both turbulent and shock acceleration of relativistic electrons have been included macroscopically. From this, the distribution of synchrotron luminosity in the remnant has been calculated. It is found that the radio morphology of model remnants expanding into a homogeneous medium does not agree with observations. Expansion into a circumstellar medium with many small cloudlets does produce radio shells which agree with observations. It is suggested that supernova remnants reflect the interaction of ejected matter with a cloudy circumstellar medium.

Dickel, John R.↗

NASA NTRS1988

Supernova 1987A

Supernova 1987A (February 23, 1987) in the Large Magellanic Cloud is the brightest supernova to be observed since SN 1604 AD (Kepler). Detection of a burst of neutrinos indicates that a neutron star was formed. Radioactive decay of about 0.07 solar mass of Co-56 is responsible for the observed optical light as well as hard X-rays and gamma-ray lines. Ultraviolet, optical, and infrared 'light echoes' and soft X-rays provide information on the distribution of circumstellar matter and the evolution of the progenitor star.

Mccray, Richard↗

NASA NTRS1989

The interaction of supernovae with circumstellar bubbles

This paper examines the interaction of a massive star supernova with the shell created by the fast wind from a blue supergiant, either in the main-sequence phase or in a late evolutionary phase. Making a number of idealizations, the general features of shell interaction are described by semianalytical solutions. The expected properties of the supernova and its environment are discussed, and the hydrodynamics of the interaction is described. It is found that, typically, the shock traversal occurs before the energy transfer is significant. Applications of the model to observed objects are considered, with special attention given to the interaction of SN 1987A with its circumstellar shell, which is expected to occur within decades.

Chevalier, Roger A.↗