[en] The number of Frenkel pairs produced per ion was measured at 5 K for various heavy ion irradiations of thin chromium films. Values much lower than those predicted by transport theory were found. The divergence of experimental and theory was correlated with the maximum elastic deposited energy density and the average concentration of Frenkel pairs. For a given ion mass, the rate at which the damage annealed out of the chromium films was dependent on the irradiation energy. The difference between the annealing rates of 20 and 100 keV ion induced damage was most prominent for the heavier masses (I⁺, Br⁺). The presence of unannealed damage at 80K suggest that at least some clustering of defects did occur. For the 20-50 keV/atom range, N⁺ and N₂⁺ ions of equal velocities had the same defect production rate. No difference in the annealing rates of the damage from these two beams was detected. It is speculated, however, that a higher mass atom would have different damage rates (per atom) associated with its monomer and dimer ions of equal velocity

[en] A small number of Type I supernovae exhibit well-defined peculiarities. In particular some Type I supernovae do not have the characteristic Si II 6150 A feature, and some do not have the 1.2μm absorption. It is noted that all supernovae which lack the infrared absorption also lack the 6150 A feature. Therefore it is proposed that these supernovae constitute a single sub-class of Type I supernovae and that the absence of Si is responsible for the lack of both the 6150 A and 1.2μm absorptions. Si is an excellent candidate as the cause of the infrared absorption because Si I has a dense array of strong lines near 1.2μm. (author)

[en] Supernova 1984A was a remarkable Type Ia event which exhibited extremely high-velocity material in its spectrum. The optical light curve of this supernova is marked by a rapid decline, which further distinguishes it from common Type Ia events, but the optical spectra are, apart from the persistent, unusually larger Doppler shifts, practically identical to previously well-observed Type Ia supernovae such as SN 1981B. In contrast to the extreme optical peculiarity of this supernova, the IR light curves are almost normal. Only one other Type I supernova is known to have a light curve which is as fast as SN 1984A-SN 1885 in M31, S Andromedae. S Andromedae has been classified as a peculiar Type I on account of its unusual light curve. But now that such a fast light curve is no longer unprecedented, S Andromedae can be classified as a Type Ia supernova. 31 references

[en] The mechanisms responsible for the observed emission spectrum of SN 1987A during May-July 1987 are considered theoretically. Particular attention is given to the increasing strength of the 1.083-micron He I emission, tentatively attributed to ionization by gamma rays from Co-56 decay. It is suggested that the onset of gamma emission escape from the SN may coincide with the He I strengthening. 27 references

[en] The white dwarf star G29-38 has an infrared excess which may be due to a cool low-mass companion, probably a brown dwarf, or to circumstellar dust. If the excess is due to dust, then changes in luminosity of the white dwarf, which is a ZZ Ceti variable, may cause the infrared excess to vary in phase with the optical pulsations. Simultaneous optical and infrared light curves of G29-38 have been obtained to search for variability of the excess. The known 614 s period of G29-39 is seen at B and J, with amplitudes and phases which are in excellent agreement with the predictions of adiabatic, g-mode pulsation theory. No variability with a 614 s period is found at K above that expected from the white dwarf photosphere. Two significant periodicities are discovered in the K light curve at 181 + or - 10 s and 243 + or - 15 s. These periods are not found at shorter wavelengths, and it is concluded that they must be due to variations in the strength of the infrared excess, rather than the photospheric emission from the white dwarf. A model is proposed which invokes a dust ring around the white dwarf to explain the infrared excess and variability in this system. 17 refs

[en] This paper reports on the discovery of a compact, unresolved infrared nucleus, coincident with the radio core, in the prototypical powerful radio galaxy Cygnus A (3C 405). The infrared colors and magnitudes of the nucleus can be explained as a highly reddened extension of the radio continuum. The implied restframe extinction is A(V) equal to about 50 + or - 30 magnitudes. The extinction-corrected luminosity of the object is in the quasar range. This discovery gives some support to the unification models for quasars and powerful radio galaxies. 35 refs

[en] The size of the emission region of NGC 4151 at 11.2 microns has been measured to be 0.16 + or - 0.04 arcsec (1 sigma). This size is in agreement with that expected from thermal emission from dust grains heated by a central luminosity source, but is inconsistent with nonthermal emission. 19 refs

[en] In a previous paper it was established that the infrared radiation observed from supernova 1982e originated from a pre-existing circumstellar dust cloud, and was produced by an echo of the radiation from the supernova. Here a model of the time-dependent radiative transfer within a supernova dust cloud is developed to allow detailed comparison of the data and the model. This analysis further confirms the original conclusion that the infrared emission is due to an echo, and permits the self-consistent derivation of several cloud parameters including the optical depth of the dust cloud and the mass of dust in the cloud. A dusty stellar wind is the most likely source of this cloud. (author)

[en] A late-type supergiant which appeared in the bulge of M31 in the last observing season faded 3 bolometric magnitudes in 100 days and is now no longer detectable. It is suggested that the object was a nova of an unusual type. 9 refs

[en] Near-infrared images at 1.25, 1.65, and 2.2 microns have been obtained of nine galaxies from the IRAS Bright Galaxy Sample with infrared luminosities greater than 10 to the 12th solar luminosities. Two of the 2.2-micron images reveal previously undetected double nuclei, increasing the number of close double nuclei known for this samples from two to four. For three of these four sources, the colors of both nuclei are substantially different from those of normal spiral galaxies, indicating that the high activity state in high-luminosity mergers tends to occur in both nuclei. Three sources show 2.2-micron emission that is more centrally concentrated than the emission at 1.3 microns, a result that can be explained as the effects of dust emission and/or extinction or, alternatively, as the result of direct emission at 2.2 microns from the accretion disk of a central active galactic nucleus. Implications of these results for the model that galaxy collisions lead to quasar formation are briefly discussed. Finally, from the frequency and separation of the double nucleus sources, the lifetime of the ultraluminous phase of galaxies is estimated to be about 400 million yr. 10 refs