2,435 research outputs found

    The Supernova Remnant G11.2-0.3 and its central Pulsar

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    The plerion inside the composite Supernova Remnant G11.2-0.3 appears to be dominated by the magnetic field to an extent unprecedented among well known cases. We discuss its evolution as determined by a central pulsar and the interaction with the surrounding thermal remnant, which in turn interacts with the ambient medium. We find that a plausible scenario exists, where all the observations can be reproduced with rather typical values for the parameters of the system; we also obtain the most likely period for the still undetected pulsar.Comment: 10 pages, to be published on ApJ Letters. Formatted using AASTe

    Precursor Plerionic Activity and High Energy Gamma-Ray Emission in the Supranova Model of Gamma-Ray Bursts

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    The supranova model of gamma-ray bursts (GRBs), in which the GRB event is preceded by a supernova (SN) explosion by a few months to years, has recently gained support from Fe line detections in X-ray afterglows. A crucial ingredient of this model yet to be studied is the fast-rotating pulsar that should be active during the time interval between the SN and the GRB, driving a powerful wind and a luminous plerionic nebula. We discuss some observational consequences of this precursor plerion, which should provide important tests for the supranova model: 1) the fragmentation of the outlying SN ejecta material by the plerion and its implications for Fe line emission; and 2) the effect of inverse Compton cooling and emission in the GRB external shock due to the plerion radiation field. The plerion-induced inverse Compton emission can dominate in the GeV-TeV energy range during the afterglow, being detectable by GLAST from redshifts zâ‰Č1.5z \lesssim 1.5 and distinguishable from self-Compton emission by its spectrum and light curve. The prospects for direct detection and identification of the precursor plerion emission are also briefly considered.Comment: ApJ vol.583, in pres

    Rapid Variability of Gamma-Ray Blazars: A Model for MKN 421

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    The extremely rapid burst of TeV photons from Mkn 421 (15 May 1996) can be reconciled with the standard properties of a relativistic gamma-ray emitting jet (bulk Lorentz factor ≈\approx 10; size \10^{17} cm) if one assumes that the electrons are accelerated in conical shocks with both opening and viewing angles ≈1/Γ\approx 1/\Gamma. If the injection time and the cooling time are much less than the photon crossing time, an emission ring moves along the jet and leads to the appearance of a very rapid flare, in satisfactory agreement with the observations.Comment: 12 pages, 3 figures, uses aasms4.sty, to appear in ApJ Letter

    Detection and characterization of viral pathogens associated with reproductive failure in wild boars in central Italy

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    Suid herpesvirus 1, porcine circovirus 2 and porcine parvovirus are causative agents of reproductive failures in swine and are widely diffused in the wild boar population. No data describing the impact of those viruses on the reproductive performance of wild boar are so far available. We aimed to investigate the ability of the above viruses to infect foetuses of free-ranging pregnant wild boar sows living in a highly-populated area. Molecular investigation revealed that although all investigated viruses were detected in pregnant sows, only herpesvirus and circovirus were detected in the foetuses. Phylogenetic analysis revealed a close relationship between the strains circulating in wild boar and those already described in domestic swine. This study highlights the importance of monitoring the circulation of pathogens that are shared between domestic and wild pigs. This information is essential for the pig industry to avoid possible economic losses. Wild boar and domestic swine share several pathogens, including viruses responsible for reproductive failures, representing an important sanitary and economic risk for the swine industry. Among them, suid herpesvirus 1 (SuHV-1), porcine circovirus 2 (PCV2) and porcine parvovirus 1 (PPV1) are widely diffused in the wild boar population. Unfortunately, little is known about their pathogenetic mechanisms and impact on the reproductive parameters of wild animals. This study aims to investigate the presence of viruses responsible for reproductive failure in pregnant wild boar sows and their foetuses. The investigation was conducted on 46 pregnant wild boar and their foetuses by molecular analysis; a phylogenetic study was performed on the positive samples. All of the investigated pathogens were identified in sows, while only herpesvirus and circovirus were detected in the tissues of their foetuses. Phylogenetic analysis revealed that the viral sequences obtained from the positive wild boars were closely related to those previously identified in domestic swine belonging to the same study areas. The results suggest that SuHV-1 and PCV2 can infect wild boar foetuses, with a possible impact on wild boar reproductive performance. Moreover, our data highlight the importance of continuous monitoring of swine pathogens circulating in wild environments, so as to carry out adequate sanitary actions
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