RESUMO
Long-duration γ-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectronvolt-to-megaelectronvolt band, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission1,2. Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands1-6. The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock7-9. Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C10,11. Here we report multi-frequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 × 10-6 to 1012 electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs.
RESUMO
Readers are invited to submit questions relating to problem cases. Inquiries will be answered by qualified consultants and replies forwarded by mail promptly. Selected problems and solutions are published every month in this section.
RESUMO
How much do employees value the various family support benefits offered by employers? A recent survey finds a correlation between employees' perceived utility of certain benefit programs and job satisfaction and performance.
Assuntos
Licença para Cuidar de Pessoa da Família/estatística & dados numéricos , Planos de Assistência de Saúde para Empregados/estatística & dados numéricos , Satisfação no Emprego , Coleta de Dados , Tomada de Decisões Gerenciais , Emprego , Estudos de Avaliação como Assunto , Planos de Assistência de Saúde para Empregados/organização & administração , Responsabilidade Social , Estados UnidosAssuntos
Antibacterianos/efeitos adversos , Infecções Bacterianas/tratamento farmacológico , Transtornos Relacionados ao Uso de Substâncias , Antibacterianos/uso terapêutico , Bronquite/tratamento farmacológico , Criança , Infecções por Escherichia coli/tratamento farmacológico , Gastroenteropatias/tratamento farmacológico , Humanos , Lactente , Laringite/tratamento farmacológico , Meningite/tratamento farmacológico , Otite Média/tratamento farmacológico , Penicilinas/efeitos adversos , Penicilinas/uso terapêutico , Faringite/tratamento farmacológico , Pneumonia Estafilocócica/tratamento farmacológico , Pneumonia Viral/tratamento farmacológico , Infecções por Salmonella/tratamento farmacológico , Infecções Estreptocócicas/tratamento farmacológico , Infecções Urinárias/tratamento farmacológicoRESUMO
The 7 year data set of the Milagro TeV observatory contains 2.2 x 10(11) events of which most are due to hadronic cosmic rays. These data are searched for evidence of intermediate scale structure. Excess emission on angular scales of approximately 10 degrees has been found in two localized regions of unknown origin with greater than 12sigma significance. Both regions are inconsistent with pure gamma-ray emission with high confidence. One of the regions has a different energy spectrum than the isotropic cosmic-ray flux at a level of 4.6sigma, and it is consistent with hard spectrum protons with an exponential cutoff, with the most significant excess at approximately 10 TeV. Potential causes of these excesses are explored, but no compelling explanations are found.
RESUMO
Gamma-ray emission from a narrow band at the galactic equator has previously been detected up to 30 GeV. We report evidence for a TeV gamma-ray signal from a region of the galactic plane by Milagro, a large-field-of-view water Cherenkov detector for extensive air showers. An excess with a significance of 4.5 standard deviations has been observed from the region of galactic longitude l E (40 degrees, 100 degrees) and latitude /b/ < 5 degrees. Under the assumption of a simple power law spectrum, with no cutoff in the EGRET-Milagro energy range, the measured integral flux is phi gamma(>3.5 TeV) = (6.4 +/- 1.4 +/- 2.1) x 10(-11) cm(-2) s(-1) sr(-1). This flux is consistent with an extrapolation of the EGRET spectrum between 1 and 30 GeV in this galactic region.