Neutrino Annihilation between Binary Neutron Stars

We calculate the neutrino pair annihilation rate into electron pairs between two neutron stars in a binary system. We present a closed formula for the energy deposition rate at any point between the stars, where each neutrino of a pair derives from each star, and compare this result to that where all neutrinos derive from a single neutron star. An approximate generalization of this formula is given to include the relativistic effects of gravity. We find that this inter-star neutrino annihilation is a significant contributor to the energy deposition between heated neutron star binaries. In particular, for two neutron stars near their last stable orbit, inter-star neutrino annihilation energy deposition is almost equal to that of single star energy deposition.Comment: 15 pages, 6 figures, accepted for publication in The Astrophysical Journa

General Relativistic Augmentation of Neutrino Pair Annihilation Energy Deposition Near Neutron Stars

General relativistic calculations are made of neutrino-antineutrino annihilation into electron-positron pairs near the surface of a neutron star. It is found that the efficiency of this process is enhanced over the Newtonian values up to a factor of more than 4 in the regime applicable to Type II supernovae and by up to a factor of 30 for collapsing neutron stars.Comment: 14 pages, 6 figure

Gamma-Ray Bursts via Pair Plasma Fireballs from Heated Neutron Stars

In this paper we model the emission from a relativistically expanding electron-positron pair plasma fireball originating near the surface of a heated neutron star. This pair fireball is deposited via the annihilation of neutrino pairs emanating from the surface of the hot neutron star. The heating of neutron stars may occur in close neutron star binary systems near their last stable orbit. We model the relativistic expansion and subsequent emission of the plasma and find 10^51 to 10^52 ergs in gamma-rays are produced with spectral and temporal properties consistent with observed gamma-ray bursts.Comment: 5 pages, 3 figures. Submitted to the Conference Proceedings of the 5th Huntsville Gamma-Ray Burst Symposiu

The unbiased frequency of planetary signatures around single and binary white dwarfs using Spitzer{\it Spitzer} and Hubble{\it Hubble}

This paper presents combined ${\it Spitzer}$ IRAC and ${\it Hubble}$ COS results for a double-blind survey of 195 single and 22 wide binary white dwarfs for infrared excesses and atmospheric metals. The selection criteria include cooling ages in the range 9 to 300 Myr, and hydrogen-rich atmospheres so that the presence of atmospheric metals can be confidently linked to ongoing accretion from a circumstellar disc. The entire sample has infrared photometry, whereas 168 targets have corresponding ultraviolet spectra. Three stars with infrared excesses due to debris discs are recovered, yielding a nominal frequency of $1.5_{-0.5}^{+1.5}$ per cent, while in stark contrast, the fraction of stars with atmospheric metals is $45\pm4$ per cent. Thus, only one out of 30 polluted white dwarfs exhibits an infrared excess at 3-4 $\mu$m in IRAC photometry, which reinforces the fact that atmospheric metal pollution is the most sensitive tracer of white dwarf planetary systems. The corresponding fraction of infrared excesses around white dwarfs with wide binary companions is consistent with zero, using both the infrared survey data and an independent assessment of potential binarity for well-established dusty and polluted stars. In contrast, the frequency of atmospheric pollution among the targets in wide binaries is indistinct from apparently single stars, and moreover the multiplicity of polluted white dwarfs in a complete and volume-limited sample is the same as for field stars. Therefore, it appears that the delivery of planetesimal material onto white dwarfs is ultimately not driven by stellar companions, but by the dynamics of planetary bodies.Comment: 15 pages, 6 figures, 3 tables; accepted for publication in MNRA

The pathological relationship between the host and parasite in varieties and strains of watermelons resistant to Fusarium Niveum E. F. S.

Watermelon plants, at all stages of growth, are liable to attack by Fusarium niveum which enters through the root tips and ruptures formed by newly developed lateral roots. Epidermal cells of the zones of elongation and maturation at the side of the root 2 to 6 mm. back of the zone of meristematic activity were as readily penetrated as meristematic tissues at the tip. After penetrating the epidermis, hyphae continued intracellularly through the cortical cells to the pericycle where the massed mycelium broke down the endodermal cell walls and entered the xylem vessels. Entrance of the pathogene through the ruptures formed by lateral roots was accompanied by the formation of lesions, intracellular penetration of the cortical and parenchymatous tissues, and disorganization of the endodermis by the action of massed hyphae, which then entered the xylem vessels. Infection of seedlings at or shortly after germination of the seed, combined with favorable conditions for the pathogene led to rapid invasion of the xylem vessels with mycelium in the primary root, accompanied by a high percentage of wilting. Older plants, repeatedly infected through young lateral roots, apparently succumbed from a series of internal pathological disturbances involving the accumulation of gum-like materials, tyloses and mycelium in the xylem vessels, particularly those of the primary root where the conductive capacity of the vessels was so reduced in time that wilting ensued. Gum-like materials and tyloses in the xylem of diseased plants seem to be produced by living cells of the host, injured by either toxic, metabolic or enzymatic products of the wilt pathogene. Older resistant plants seemingly withstood attacks of the wilt pathogene, which in seedlings often proved fatal. Apparently no well developed defense mechanism had time to develop and function in the early seedling stage. It was significant that resistant plants, which survived in fields heavily infested with Fusarium niveum had bands of gum-like material surrounding the older xylem near the center of the root axis, while the secondary xylem at the periphery of the stele remained unaffected. On the other hand, wilted susceptible plants were filled with gum-like materials throughout the primary root xylem. Neither resistant nor susceptible plants, grown in soils free of the wilt pathogene, had appreciable quantities of gum-like materials and tyloses in the primary root xylem. Greenhouse indexing of resistant seedlings has proved of value in the Iowa Belle and Pride of Muscatine varieties, but, with the dosage of inoculum employed, Iowa King selections failed to show measurable diffcrences in resistance when compared with susceptible checks. In 4 years, field studies on soils heavily infested with the wilt pathogene, resistant plants seemed more resistant with age, the heaviest mortality being within the first 16 to 24 days, after which few plants wilted; susceptible checks continued to wilt throughout the season. Changes in air and soil temperatures and precipitation retarded or accelerated wilting for periods of 1 to several days; however, irrespective of environmental factors, there was an upward trend in the percentage average daily wilt, which reached a maximum at 23 to 39 days after planting susceptible seedlings and at 16 to 24 days with resistant seedlings. Pride of Muscatine, Iowa King and Iowa Belle have proved to be suitable stock for the transmission of resistance. the last named variety being especially desirable as a resistant parent. Backcrossing the F1 hybrid (resistant x susceptible variety) to the resistant parent has proved the most effective method of building up resistance when susceptible and resistant lines were involved

On Evolution of the Pair-Electromagnetic Pulse of a Charge Black Hole

Using hydrodynamic computer codes, we study the possible patterns of relativistic expansion of an enormous pair-electromagnetic-pulse (P.E.M. pulse); a hot, high density plasma composed of photons, electron-positron pairs and baryons deposited near a charged black hole (EMBH). On the bases of baryon-loading and energy conservation, we study the bulk Lorentz factor of expansion of the P.E.M. pulse by both numerical and analytical methods.Comment: A&A macros, 2 pages, 1 figure and postscrit file. To appear in A&A Suppl. Series, Proceeding of Rome98 GRB workshop, ed. L. Pira and F. Fronter