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At least 91 records · Page 5
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DOE OSTI2025

Strontium-84 Enrichments in Presolar Grains Provide First Evidence of p -process Nucleosynthesis in Core-collapse Supernovae

This study reports detection of rare p-process isotopes within presolar grains. Presolar grains are relic dust grains from dying stars. These microscopic dust particles are found in primitive solar system materials. Their distinct isotopic compositions record the nucleosynthetic processes in their parent stars and the Galactic chemical environment in which these stars formed. We studied presolar graphite grains of high-density type from the Murchison meteorite and found five grains with subgrains that show enrichments in 84 Sr compared to the solar abundance. 84 Sr is the neutron-deficient isotope of strontium that can be produced in the deep oxygen-rich interior of high-mass stars that end their lives as core-collapse supernovae. The observed 84 Sr excesses cannot be produced in low-mass asymptotic giant branch stars, the source of most high-density presolar graphites found in meteorites. High-density graphites with embedded 84 Sr excesses are, instead, compatible with a core-collapse supernovae origin. The graphite subgrains condensed from carbon-rich materials in the outer layers of core-collapse supernovae, where 84 Sr was destroyed by neutron captures during hydrostatic evolution of the stars and their final explosion. Based on current theoretical stellar models, a few percent of contribution from the inner regions of core-collapse supernovae, which are enriched in p-process nuclides, to the outer carbon-rich regions is the most likely explanation for the observed enrichment of 84 Sr in the subgrains of the high-density graphites. In this study, we present the first observational evidence that core-collapse supernovae produce and eject isotopes made by the p-process.

Astronomy and AstroPhysics↗
NASA NTRS1978

Supernovae and the formation of the solar system

The evidence that a supernova explosion may have triggered the formation of the solar system is reviewed. It cannot be said on the basis of the investigation that the supernova trigger is absolutely necessary for planetary system formation. However, it does appear according to the isotopic evidence that a supernova did blow up within a few million years of the solidification of objects in the solar system. If such an event occurred, it is reasonable to assume that the resultant supernova shock had a causal connection with the formation of the solar system and that a supernova may be one stimulus for formation of low-mass stars.

Schramm, D. N.↗
NASA NTRS1979

An upper limit for the total energy of relativistic particles contained in the early stages of supernova explosions

A model is proposed for the emission of X-rays from supernova explosions wherein the thermal distribution of photons from a supernova photosphere is inverse Compton scattered by relativistic electrons within or near the surface of the star. Using this model, upper limits for the number of relativistic electrons and their total energy are established on the basis of upper limits to the observed X-ray luminosity of a supernova during maximum light. These upper limits, in conjunction with radio frequency upper limits obtained by Brown and Marscher, strongly suggest that supernovae do not produce significant numbers of relativistic particles until at least 70 years after the initial outburst. This, in turn, implies that young supernovae cannot account for the radio and X-ray variability of active galactic nuclei and quasars.

Beall, J. H.↗
NASA NTRS1979

Supernovae - A new selection effect

A sample of 228 supernovae that occurred in galaxies with known redshifts is used to show that the mean projected linear supernova distance from the center of the parent galaxy increases with increasing redshift. This effect is interpreted as an observational bias: the discovery rate of supernovae is reduced in the inner parts of distant, poorly resolved galaxies. Even under the optimistic assumption that no selection effects work in galaxies closer than 33 Mpc, about 50% of all supernovae are lost in the inner regions of galaxies beyond 150 Mpc. This observational bias must be taken into account in the derivation of statistical properties of supernovae.

Shaw, R. L.↗
NASA NTRS1981

Two X-ray supernova remnants - G296.1 - 0.7 and 1E 1149.4 - 6209

Using the imaging X-ray detectors on the Einstein Observatory, what appear to be two overlapping galactic supernova remnants are discovered, one of which is clearly identified with the previously cataloged radio remnant G296.1-0.7. The other feature has no radio or optical counterpart. It is a nearly complete ring with a diameter of 20-25 arcmin, designated 1E 1149.4-6209. Because of its morphology, because there is evidence for supernova events in the vicinity, and because there seems to be no plausible alternative, 1E 1149.4-6209 is classified as a supernova remnant. This remnant and others like it, which may be found first in X-rays rather than radio or optical waves, may have important implications regarding the evolution of supernova remnants and the rate of supernovae in our Galaxy.

Markert, T. H.↗
NASA NTRS1982

An optimist's guide to supernovae

There are some hints that a satisfactory agreement between observations and models is developing in several areas of supernova research. The light curves and spectra of Type I supernovae look so much like the models that they may well have their origin in the synthesis of Ni-56 in the explosion of a compact star. Type II supernovae are found where massive stars form, have light curves that correspond to 10 to the 51st ergs suddenly deposited inside a red supergiant, and may in fact be the explosions of massive stars. Some young supernova remnants, such as Cas A, show abundance patterns that bear a striking resemblance to those seen deep inside models of massive stars on the verge of destruction. Observations of old supernova remnants provide energy estimate of 10 to the 51st ergs - just the amount needed for the models of the outbursts.

Kirshner, R. P.↗
NASA NTRS1983

The infrared echo of a type II supernova with a circumstellar dust shell - Applications to SN 1979c and SN 1980k

Merrill (1980) and Telesco et al. (1981) have reported observations according to which supernovae developed a thermal infrared excess about 7-9 months after visual maximum. The two supernovae involved are SN 1979c in NGC 4321 and SN 1980k in NGC 6946. The infrared behavior of these supernovae is almost identical to that observed in several novae. The present investigation is concerned with the question whether the thermal infrared radiation from SN 1979c and SN 1980k could have been emitted by dust particles which were present in a circumstellar shell prior to the supernova event. The obtained results confirm the suggestion of Bode and Evans (1980) that the thermal emission from SN 1979c may have originated from preexisting dust present in a circumstellar shell and heated up by the UV-visual output of the supernova. The thermal infrared emission from SN 1980k may have a similar origin.

Dwek, E.↗
NASA NTRS1984

Interstellar absorption lines in the spectrum of supernova Evans in M83 (NGC 5236)

It is pointed out that supernovae in other galaxies create spontaneous opportunities to probe spectroscopically the gaseous material in galactic halos. Because of their brightness, supernovae offer an unparalleled chance to obtain spectra with high wavelength resolution and/or signal-to-noise ratio. The present investigation is concerned with observations of visual interstellar lines in the spectrum of a supernova discovered on July 3, 1983, and identified as Type I. The supernova was located 124 arc sec south and 122 arc sec west of the nucleus of M83. Evidence is obtained that for velocities near that of M83, the line of sight toward the supernova contains a complex array of absorption features of Ca II. In both Ca II and Na I, the absorptions associated with M83 are far more prominent than those halfway through the disk (and halo) of the Milky Way Galaxy. It is felt that many of the displaced velocity components in the M83 system arise from a gaseous halo.

Rodgers, A. W.↗
NASA NTRS1988

Infrared supernova light curves and asymmetric stellar mass loss

Infrared dust emission echos from Type II supernovae are a natural consequence of the heating of circumstellar dust by the supernova light. Red supergiants, the likely progenitors of most Type II supernovae, are known in some cases to have asymmetric circumstellar envelopes. It is noted that an asymmetric dust distribution can have a substantial effect on the evolution of an infrared echo and results are presented for an ellipsoidal dust distribution. The angle between the symmetry axis and the line of sight is unknown in any particular case so that detailed observations of a number of supernovae will be necessary to test for asymmetries. Asymmetries may also be observable in the radio structure of supernovae and in a possible scattered-light echo.

Emmering, Robert T.↗
NASA NTRS1988

Supernova 1987A - A radiosphere resolved with VLBI five days after the neutrino burst

The results of VLBI observations of SN1987A are reported. No emission from the supernova above a level of about 20 percent of the supernova's total flux density was detected, although signals were detected from two calibrator sources with amplitudes roughly equal to those determined in earlier VLBI observations. It is inferred that the supernova's radiosphere was resolved, and a lower bound on the radiosphere's radius of 2.2 mas is estimated from an epoch 5.2 days after the neutrino burst. Given the photometric data from the supernova, a distance to the LMC of 50 + or - 5 kpc, and an apparent expansion velocity that varied systematically with time from 18,000-16,000 km/s, as estimated from the blue-shifted H-alpha absorption lines on the days preceding the observations, it is concluded that 5.2 days after the neutrino burst the supernova's radiosphere was at least 2.5 times larger than the inferred blackbody photosphere, and at least as large as the H-alpha line-forming region.

Jauncey, D. L.↗
NASA NTRS1987

Gravitational lensing of supernovae by dark matter candidates of mass M greater than about 0.001 solar masses

A review is presented concerning the gravitational lensing of supernovae by intervening condensed objects, including dark matter candidates such as dim stars and black holes. the expansion of the supernova beam within the lens produces characteristic time-dependent amplification and polarization which depend upon the mass of the lens. The effects of the shearing of the beam due to surrounding masses are considered, although the study of these effects is confined to isolated masses whose size is much less than that of the supernova (about 10 to the 15th cm). Equations for the effects of lensing and graphs comparing these effects in different classes of supernovae are compared. It is found that candidates for lensing would be those supernovae at least as bright as their parent galaxy, or above the range of luminosities expected for their spectral class.

Wagoner, Robert V.↗
NASA NTRS1988

On relative supernova rates and nucleosynthesis roles

It is shown that the Ni-56-Fe-56 observed in SN 1987A argues that core collapse supernovae may be responsible for more that 50 percent of the iron in the galaxy. Furthermore it is argued that the time averaged rate of thermonuclear driven Type I supernovae may be at least an order of magnitude lower than the average rate of core collapse supernovae. The present low rate of Type II supernovae (below their time averaged rate of approx. 1/10 yr) is either because the past rate was much higher because many core collapse supernovae are dim like SN 1987A. However, even in this latter case they are only an order of magnitude dimmer that normal Type II's due to the contribution of Ni-56 decay to the light curve.

Arnett, W. David↗
NASA NTRS1989

On relative supernova rates and nucleosynthesis roles

It is shown that the Ni-56-Fe-56 observed in SN 1987A argues that core collapse supernovae may be responsible for more than 50 percent of the iron in the galaxy. Furthermore it is argued that the time averaged rate of thermonuclear driven Type I supernovae may be at least an order of magnitude lower than the average rate of core collapse supernovae. The present low rate of Type II supernovae (below their time averaged rate of approx. 1/10 yr) is either because the past rate was much higher because many core collapse supernovae are dim like SN 1987A. However, even in this latter case they are only an order of magnitude dimmer that normal Type II's due to the contribution of Ni-56 decay to the light curve.

Arnett, W. David↗
NASA NTRS1989

IR line emission from supernovae in molecular clouds

The absorption of the x rays from a supernova explosion in the surrounding molecular gas is discussed. A supernova explosion in a molecular cloud results in a supernova remnant which radiates a fraction of the approximately 10 to the 51st power erg kinetic energy of the supernova explosion in the form of x rays. The absorption of these x rays in the surrounding molecular gas produces ionization, dissociation, and heating. It is found that a 10(exp 51) erg supernova explosion in a uniform molecular cloud of density equal to 1000 per cubic centimeter results in the emission of photons in the H2 line. This process may contribute appreciably to the strong S(1) line emission seen from some starburst galaxies, such as NGC 6240.

Draine, B. T.↗
NASA NTRS1991

Gamma ray constraints on the Galactic supernova rate

We perform Monte Carlo simulations of the expected gamma ray signatures of Galactic supernovae of all types to estimate the significance of the lack of a gamma ray signal due to supernovae occurring during the last millenium. Using recent estimates of the nuclear yields, we determine mean Galactic supernova rates consistent with the historic supernova record and the gamma ray limits. Another objective of these calculations of Galactic supernova histories is their application to surveys of diffuse Galactic gamma ray line emission.

Hartmann, D.↗
NASA NTRS1992

Gamma ray constraints on the galactic supernova rate

Monte Carlo simulations of the expected gamma-ray signatures of galactic supernovae of all types are performed in order to estimate the significance of the lack of a gamma-ray signal due to supernovae occurring during the last millenium. Using recent estimates of nuclear yields, we determine galactic supernova rates consistent with the historic supernova record and the gamma-ray limits. Another objective of these calculations of galactic supernova histories is their application to surveys of diffuse galactic gamma-ray line emission.

Hartmann, D.↗
NASA NTRS1994

Inside the supernova: A powerful convective engine

We present an extensive study of the inception of supernova explosions by following the evolution of the cores of two massive stars (15 and 25 Solar mass) in multidimension. Our calculations begin at the onset of core collapse and stop several hundred milliseconds after the bounce, at which time successful explosions of the appropriate magnitude have been obtained. Similar to the classical delayed explosion mechanism of Wilson, the explosion is powered by the heating of the envelope due to neutrinos emitted by the protoneutron star as it radiates the gravitational energy liberated by the collapse. However, as was shown by Herant, Benz, & Colgate, this heating generates strong convection outside the neutrinosphere, which we demonstrate to be critical to the explosion. By breaking a purely stratified hydrostatic equilibrium, convection moves the nascent supernova away from a delicate radiative equilibrium between neutrino emission and absorption, Thus, unlike what has been observed in one-dimensional calculations, explosions are rendered quite insensitive to the details of the physical input parameters such as neutrino cross sections or nuclear equation of state parameters. As a confirmation, our comparative one-dimensional calculations with identical microphysics, but in which convection cannot occur, lead to dramatic failures. Guided by our numerical results, we have developed a paradigm for the supernova explosion mechanism. We view a supernova as an open cycle thermodynamic engine in which a reservoir of low-entropy matter (the envelope) is thermally coupled and physically connected to a hot bath (the protoneutron star) by a neutrino flux, and by hydrodynamic instabilities. This paradigm does not invoke new or modified physics over previous treatments, but relies on compellingly straightforward thermodynamic arguments. It provides a robust and self-regulated explosion mechanism to power supernovae that is effective under a wide range of physical parameters.

Herant, Marc↗
NASA NTRS1995

High-velocity, high-excitation neutral carbon in a cloud in the Vela supernova remnant

HD 72089 is situated behind the Vela supernova remnant, and the interstellar absorption lines in the spectrum of this star are remarkable for two reasons. First, there are six distinct velocity components that span the (heliocentric) velocity range -60 to +121 km/s in the lines of Na I and Ca II. Second, two of the components at high velocity, one at +85 km/s and another at +121.5 km/s, have densities that are large enough to produce observable lines from neutral carbon. The gas moving at +121.5 km/s has such a large pressure that the excited fine-structure levels of the ground electronic state of C I are collisionally populated nearly in proportion to their level degeneracies. This high-velocity gas exhibits unusually low column densities of Mg I and Na I, compared to that of C I. We propose that the +121.5 km/s component represents gas that has cooled and recombined in a zone that follows a shock driven into a cloud by the very recent passage of a supernova blast wave. A representative preshock density of n(sub H) approximately = 13/cc and velocity v(sub s) = 100 km/s is indicated by the strength of diffuse (O III) emission lines seen in directions very near HD 72089. The strong collisional population of excited C I and apparent absence of excited levels of O I give a most favorable fit to the conditions 1000 less than n(sub H) less than 2900/cc over a temperature range 300 less than T less than 1000 K. The fact that the compression is not substantially more than this indicates that the preshock gas may have had an embedded, transverse magnetic field with a strength B greater than or approximately = 1 micro-G. The large dynamical pressure of the supernova blast wave that would be needed to create the cloud shock that we describe implies that the energy of the supernova was 8 x 10(exp 51) ergs, if the Vela remnant is 500 pc away. We can bring this value much closer to typical supernova energies E less than or approximately = 10(exp 51) ergs if the distance to the remnant is revised downward by at least a factor of 2.

Jenkins, Edward B.↗