577 research outputs found

    A White Dwarf Merger Paradigm for Supernovae and Gamma-Ray Bursts

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    Gamma-ray bursts can appear to be a hundred times as luminous as supernovae, but their underlying energy source(s) have remained a mystery. However, there has been evidence for some time now of an association of gamma-ray bursts with supernovae of Type Ib and Ic, a fact which has been exploited by a number of models, to explain the gamma-ray burst phenomenon. Here we interpret the results of basic observations of SN 1987A and of pulsars in globular clusters, to propose the energy source, which powers at least some long-duration gamma-ray bursts, as core-collapse following the merger of two white dwarfs, either as stars or stellar cores. The beaming and intrinsic differences among gamma-ray bursts arise, at least in part, from differing amounts and composition of the gas in the merged stellar common envelopes, with the more energetic bursts resulting from mergers within less massive envelopes. In order for the beams/jets associated with gamma-ray bursts to form in mergers within massive common envelopes (as with SN 1987A), much of the intervening stellar material in the polar directions must be cleared out by the time of core-collapse, or the beams/jets themselves must clear their own path. The core-collapse produces supernovae of Type Ib, Ic, or II (as with SN 1987A, a SNa IIp), leaving a weakly magnetized neutron star remnant with a spin period near 2 milliseconds. There is no compelling reason to invoke any other model to account for gamma-ray bursts. Far from being an unusual event, SN 1987A is typical, having the same merger source of initiation as 95% of all supernovae, the rare exceptions being Ia's induced via gradual accretion from a binary companion, and Fe catastrophe II's.Comment: 11 pages, 0 figures. Accepted for publication in ApJ Letter

    Pulsar-driven Jets in Supernovae, Gamma-Ray Bursts, and the Universe

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    The bipolarity of Supernova 1987A can be understood through its very early light curve observed from the CTIO 0.4-m telescope and IUE FES, and following speckle observations of the `Mystery Spot' by two groups. These indicate a highly directional beam/jet of light/particles, with initial collimation factors in excess of 10,000 and velocities in excess of 0.95 c, as an impulsive event of up to 1e-5 solar masses interacting with circumstellar material. These can be produced by a model proposed in 1972, by Bolotovskii and Ginzburg, which employs pulsar emission from polarization currents induced/(modulated faster than c) beyond the pulsar light cylinder by the periodic electromagnetic field (supraluminally induced polarization currents -- SLIP). SLIP accounts for the disruption of progenitors in supernova explosions and their anomalous dimming at cosmological distances, jets from Sco X-1 and SS 433, the lack/presence of intermittent pulsations from the high/low luminosity low mass X-ray binaries, long/short gamma-ray bursts and predicts that their afterglows are the pulsed optical/near infrared emission associated with these pulsars. SLIP may also account for the TeV e+/e- results from PAMELA and ATIC, the WMAP `Haze'/Fermi `Bubbles', and the r-process. SLIP jets from SNe of the first stars may allow galaxies to form without dark matter, and explain the peculiar, non-gravitational motions observed from pairs of distant galaxies by GALEX.Comment: This article has been published in the open source journal, Advances in Astronomy: http://www.hindawi.com/journals/aa/2012/898907 This arXiv version is out of date. arXiv admin note: substantial text overlap with arXiv:0909.2604 (Note: but less so by v2, Also Brook Sandford in Ackn. -JM

    Directional spectra comparisons between HF radar and a wave model

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    Directional spectra measurements using HF radar are compared with model data to confirm limitations of the currently available theory that underpins these measurements. In high seas, waveheight is overestimated but it is demonstrated that there is no clear impact on the shape of the spectrum which is in reasonable agreement with the model. The need for increased averaging before inversion is discussed

    Nature of cyclical changes in the timing residuals from the pulsar B1642-03

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    We report an analysis of timing data for the pulsar B1642-03 (J1645-0317) gathered over the 40-year time span between 1969 and 2008. During this interval, the pulsar experienced eight glitch-like events with a fractional increase in the rotation frequency Deltanu/nu=(0.9-2.6)x10^{-9}. We have revealed two important relations in the properties of these peculiar glitches. The first result shows that there is a strong linear correlation between the amplitude of the glitch and the time interval to the next glitch. The second result shows that the amplitude of the glitches is modulated by a periodic large-scale sawtooth-like function. As a result of this modulation, the glitch amplitude varies discretely from glitch to glitch with a step of 1.5x10^{-9} Hz in the range (2.4-6.9)x10^{-9} Hz. The post-glitch time interval also varies discretely with a step of about 600 days in the range 900-2700 days. An analysis of the data showed that three modulation schemes with modulation periods of 43 years, 53 years and 60 years are possible. The best model is the 60-year modulation scheme including 12 glitches. We make a conclusion that the nature of the observed cyclical changes in the timing residuals from PSR B1642-03 is a continuous generation of peculiar glitches whose amplitudes are modulated by a periodic large-scale sawtooth-like function. As the modulation function is periodical, the picture of cyclical timing residuals will be exactly repeated in each modulation period or every 60 years.Comment: 26 pages, 9 figures. Accepted for publication in the Astrophysical Journa
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