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NASA NTRS1989

IUE investigations of SN 1987A

IUE observations of the SN 1987A began shortly after the discovery and have been frequent through 1988 and 1989, using the fine error sensor for photometry, low dispersion spectra for the supernova spectrum, and high dispersion observations for the interstellar medium when the supernova was bright and for circumstellar gas surrounding the supernova as the initial event faded. The UV data were very useful in determining which star exploded, assessing the ionizing pulse produced as the shock hit the surface of the star, and in constraining the stellar evolution that preceded the explosion through observations of a circumstellar shell.

Kirshner, Robert P.↗

NASA NTRS1988

ISM chemical abundances in two intermediate-velocity clouds in the line of sight to SN 1987A

The earliest IUE high-resolution spectra of SN 1987A have been studied and reveal the presence of several clouds in the line of sight to the LMC. In particular, there are two clouds with radial velocities of about 130 km/s and about 180 km/s. These clouds' velocities are between those of Galactic clouds at 0-80 km/s and those of LMC gas at about 270 km/s. Chemical-abundance determinations may help to determine the origin and location of these clouds. Curve-of-growth analysis and 21-cm observations show that they may be underabundant in heavy elements by about a factor of 2 as compared to solar abundances. No depletion indicative of grain formation can be seen.

Morgan, Siobahn↗

NASA NTRS1988

Upper limits to the high-energy gamma-ray and hard X-ray flux from SN 1987A on day 55

A balloon-borne experiment was carried out on April 19, 1987 from Alice Springs, Australia to detect high-energy gamma-rays and hard X-rays from the supernova SN 1987A in the Large Magellanic Cloud. An optical spark chamber for measuring the high-energy gamma-rays and a multiwire proportional counter for measuring the hard X-rays shared a common balloon platform. No positive emission was observed by either detector. The gamma-ray upper limit obtained indicates that either the expanding supernova shell was opaque to gamma-rays at the time of the flight, or that the supernova cosmic ray luminosity was less than about 10 to the 40th erg/s. The X-ray upper limit obtained confirms the opacity of the shell to Comptonized hard X-rays.

Sood, R. K.↗

NASA NTRS1988

Gamma-ray observations of Co-56 in SN 1987A

During observations of SN 1987A 286 days after the supernova explosion using a JPL high-resolution gamma-ray spectrometer, a line feature was found in the net supernova spectrum at an energy of 1240.8 + or - 1.7 keV, with an intrinsic width of 8.2 + or - 3.4 keV FWHM, and a net flux of 0.0021 + or - 0.0007 photons/sq cm per s. This feature is interpreted as the 1238 keV line from the decay of Co-56 in the supernova remnant. The blueshift and intrinsic broadening of the 1238 keV line are consistent with models incorporating mixing of the radioactive cobalt in the expanding eject.

Mahoney, W. A.↗

NASA NTRS1988

High-resolution observations of gamma-ray line emission from SN 1987A

Observations of SN 1987A made with a balloon-borne gamma-ray spectrometer comprising an array of high-purity germanium detectors on October 29-31, 1987 are presented. High resolution data, typically 2.5 keV at 1.33 MeV, were obtained for two transists of the supernova with interspersed background data. A preliminary estimation of line flux is presented. It is found that there is evidence of dynamical broadening of the 847 keV line. It is suggested that this line may be an emission from the first excited state of Fe-56 due to the radioactive decay of Co-56 providing evidence for nucleosynthesis in the supernova.

Sandie, W. G.↗

NASA NTRS1989

Limits to the radiative decays of neutrinos and axions from gamma-ray observations of SN 1987A

Gamma-ray observations obtained by the SMM gamma-ray spectrometer in the energy range 4.1-6.4 MeV are used to provide limits on the possible radiative decay of neutrinos and axions emitted by SN 1987A. For branching ratio values for the radiative decay modes of less than about 0.0001, the present limits are more stringent than those based upon the photon flux from decaying relic neutrinos. The data are also used to set an axion mass limit.

Kolb, Edward W.↗

NASA NTRS1988

Infrared spectroscopy of SN 1987A from the NASA Kuiper Airborne Observatory

The near-infrared (1.5-3.0 microns) spectrum of SN 1987A was recorded on UT 16.3 April 1987 from the NASA Kuiper Airborne Observatory. The dominant spectral features included multicomponent P-alpha emission at 1.9 micron and a sharp edge in the continuum at 2.7 microns. The interpretation of these features relates to physical conditions in the supernova atmosphere and to the role of dust around supernovae.

Larson, H. P.↗

NASA NTRS1988

Neutrinos from SN 1987A and cooling of the nascent neutron star

The implications of the detection of neutrinos from SN 1987A for the cooling of the nascent neutron star are considered. The nu-bar(e) number N, the apparent temperature, the cooling time scale measured by the Kamioka and IMB detectors, and the inferred neutron star apparent radius and binding energy are all found to provide striking verification of current supernova theory.

Lamb, D. Q.↗

NASA NTRS1988

Gamma-ray observations of SN 1987A with an array of high-purity germanium detectors

A balloonborne gamma-ray spectrometer comprising an array of high-purity n-type germanium (HPGe) detectors surrounded by an active NaI(T1) collimator and Compton suppressing anticoincidence shield was flown on May 29-30, 1987. The average column depth of residual atmosphere in the direction of SN 1987A at float altitude was 6.3 g/sq cm during the observation. The 3-sigma upper limit obtained for the 1238-keV line from Co-56 is 0.0013 photons/sq cm s. The corresponding limit for the 847-keV line is 0.0017 photons/sq cm s.

Sandie, W. G.↗

NASA NTRS1988

The NASA SN 1987A program - Gamma-ray observations

The existing and planned experiments for making gamma-ray observations of SN 1987A are reviewed. The main emphasis is on the NASA program which consists primarily of balloon-borne instruments. Some 11-13 experiments are or will be available. Four have already flown from Alice Springs, Australia with null results. Long duration flights from Australia to South America are planned for January 88 and 89.

Teegarden, B. J.↗

NASA NTRS1989

Sanduleak's Star (LMC Anonymous) - Its similarity in the far-ultraviolet with the luminous object Eta Carinae and SN 1987A

Low-resolution IUE SWP spectra of the peculiar object LMC Anonymous (Sanduleak's Star) indicates strong evidence for CNO-processed nebula in the vicinity of the star. The far-UV spectrum of LMC Anonymous closely resembles that of the S Condensation of Eta Carinae. The similarity between LMC Anonymous and the S Condensation is apparent from the absolute intensity of the N V, semiforbidden N IV, and semiforbidden N III emission lines compared with the reduced strength of C IV or semiforbidden C III emission. IUE spectra of the S Condensation and SN 1987A may provide important clues concerning the nature of LMC Anonymous, which indicates departures from normal cosmic abundances of nitrogen relative to carbon that are extreme. This may suggest that carbon envelope burning and dredge-up occurred simultaneously during the helium-burning stage.

Michalitsianos, A. G.↗

NASA NTRS1988

Recent results on SN 1987A

The results from observational studies of SN 1987A are reviewed. The evolution of the blue supergiant pre-supernova star is examined, including the composition and core structure of the star and nitrogen enhancements. The study of heavy elements and isotopes in the ejecta is discussed. Also, consideration is given to possible mixing of supernova composition in velocity space, the profiles of observed IR lines and their red-shifted wings, and the question of what happened to the neutron star.

Woosley, S. E.↗

NASA NTRS1988

High energy gamma-ray observations of SN 1987A

Results are presented from observations of SN 1987A made with a combined high energy gamma ray and hard X-ray payload carried on a balloon flight over Alice Springs, Australia on April 5, 1988. The payload instrumentation is described, emphasizing the characteristics of the gamma-ray detector. The gamma-ray emission profile is illustrated and the preliminary results of the observations are summarized.

Sood, R. K.↗

NASA NTRS1990

A systematic study of superconductivity in BiPb(Sn)-Sb Sr-Ca-Cu-O systems

Superconducting transition above 160 K has been reported in the Bi-Pb-Sb-Sr-Ca-Cu-O system. Results of a systematic study emphasizing the correlations between the type and amount of dopant, and superconducting transition is presented. The effect of Sn (instead of Pb) substitution is also highlighted.

Akbar, Sheikh A.↗

NASA NTRS1989

Gamma rays, X-rays, and optical light from the cobalt and the neutron star in SN 1987A

Recent developments in modeling the X-ray and gamma-ray emission from SN 1987A are discussed by taking into account both the decaying cobalt and the buried neutron star. The light curve and the spectra evolution of X-rays and gamma-rays are well modeled up to day of about 300 if mixing of Co-56 into hydrogen-rich envelope is assumed. However, the 16-28 keV flux observed by Ginga declines very slowly, whereas the spherical mixing model predicts that the flux should have decreased by a large factor at t greater than 300d. It is shown that this problem can be solved if the photoelectric absorption of X-rays is effectively reduced as a result of the formation of chemically inhomogeneous clumps. Based on the adopted hydrodynamical model and the abundance distribution, predictions are offered for future optical, X-ray, and gamma-ray light curves by taking into account other radioactive sources and various types of the central source, e.g., a buried neutron star accreting the reinfalling material or an isolated pulsar.

Kumagai, Shiomi↗

NASA NTRS1989

Signatures of particle acceleration at SN 1987A

At least eight experiments are currently monitoring SN 1987A for photons or neutrinos with energies in the TeV range or higher. Observation of such signals would indicate that the supernova is the site of acceleration of charged particles to even higher energies. The way that the acceleration might occur is discussed, and the prospects for detection of such signals in light of current limits on power in the supernova from sources other than the nickel-cobalt-iron decay chain are evaluated. It is pointed out that signals of particle acceleration may show up in continuum MeV gamma rays as well as in the 100 MeV range.

Gaisser, T. K.↗

NASA NTRS1989

Hard emission at late times from SN 1987A

A model for the explosion that has been successful in predicting and explaining the evolution of SN 1987A during its first one and one-half years is used to calculate the future photometric evolution of the supernova in the UV-optical-IR, X-ray, and gamma-ray bands using Monte Carlo techniques. Special attention is given to the contribution from radioactive isotopes other than Co-56, notably Co-57, Ti-44, and Na-22, and to the possible appearance, probably within the next year, of X-rays from an accreting magnetic neutron star at the center of the supernova. The signature of a radio pulsar like the Crab is also considered. In both cases the time history of the bolometric light curve may be a more sensitive diagnostic than the existence of either pulses or hard emission, but will become confused in the near future by contributions from the rare radioactivities. A source as faint as the pulsed emission of the Crab pulsar will never be discernable in the bolometric light curve. Pulsed hard emission is best sought near 30 keV near the end of 1989 (and thereafter), although more sensitive instrumentation than hitherto employed may be necessary.

Woosley, S. E.↗

NASA NTRS1989

Search for soft X-ray emission from SN 1987A with a CCD X-ray imaging spectrometer

The results of soft X-ray observations of SN 1987A over the energy band 0.65-2.0 keV are reported. The upper limits on the soft X-ray flux are inconsistent with an extrapolation of the spectrum measured by the Ginga Satellite to the energy band and require a turnover in the X-ray spectrum between 2 and 4 keV. If this turnover is due to absorption by intervening material, a neutral column density associated with the supernova of at least 2.8 x 10 to the 21st/sq cm is required. The background rate for the Texas Instruments 800 x 800 pixel CCD, measured between 150 and 285 km altitude, was 1.1 counts/sq cm s. The background spectrum has a broad peak at 350 electrons, corresponding to charge deposited in the detector by minimally ionizing particles.

Burrows, D. N.↗