GeV Emission from Prompt and Afterglow Phases of Gamma-Ray Bursts

We investigate the GeV emission from gamma-ray bursts (GRBs), using the results from the Energetic Gamma Ray Experimental Telescope (EGRET), and in view of the Gamma-ray Large Area Space Telescope (GLAST). Assuming that the conventional prompt and afterglow photons originate from synchrotron radiation, we compare an accompanying inverse-Compton component with EGRET measurements and upper limits on GeV fluence, taking Klein-Nishina feedback into account. We find that EGRET constraints are consistent with the theoretical framework of the synchrotron self-Compton model for both prompt and afterglow phases, and discuss constraints on microphysical parameters in both phases. Based on the inverse-Compton model and using EGRET results, we predict that GLAST would detect GRBs with GeV photons at a rate >~20 yr^{-1} from each of the prompt and afterglow phases. This rate applies to the high-energy tail of the prompt synchrotron emission and to the inverse-Compton component of the afterglow. Theory predicts that in a large fraction of the cases where synchrotron GeV prompt emission would be detected by GLAST, inverse-Compton photons should be detected as well at high energies >~10 GeV. Therefore GLAST will enable a more precise test of the high-energy emission mechanism. Finally, we show that the contribution of GRBs to the flux of the extragalactic gamma-ray background measured with EGRET is at least 0.01% and likely around 0.1%.Comment: 11 pages, 7 figures; accepted by Ap

Evidence for Post-Quiescent, High-Energy Emission from Gamma-Ray Burst 990104

It is well known that high-energy emission (MeV-GeV) has been observed in a number of gamma-ray bursts, and temporally-extended emission from lower energy gamma rays through radio wavelengths is well established. An important observed characteristic of some bursts at low energy is quiescence: an initial emission followed by a quiet period before a second (postquiescent) emission. Evidence for significant high-energy, postquiescent emission has been lacking. Here we present evidence for high-energy emission, coincident with lower energy emission, from the postquiescent emission episode of the very bright and long burst, GRB 990104. We show light curves and spectra that confirm emission above 50 MeV, approximately 152 seconds after the BATSE trigger and initial emission episode. Between the initial emission episode and the main peak, seen at both low and high energy, there was a quiescent period of ~100 s during which the burst was relatively quiet. This burst was found as part of an ongoing search for high-energy emission in gamma-ray bursts using the EGRET fixed interval (32 s) accumulation spectra, which provide sensitivity to later, high-energy emission that is otherwise missed by the standard EGRET BATSE-triggered burst spectra.Comment: 5 pages, including 5 figures. Missing citation added to introduction. Accepted for publication in ApJ

Os efeitos do distanciamento social sobre a frequência alimentar e o estilo de vida de moradores do Rio Grande do Sul / The effects social distancing about food frequency and lifestyle of residents of Rio Grande do Sul

A pandemia causada pelo COVID-19 afetou o estilo de vida da população mundial, principalmente devido às políticas de distanciamento social adotadas. O objetivo dessa pesquisa transversal é avaliar a frequência do consumo alimentar e os hábitos de vida de moradores com mais de 18 anos do Rio Grande do Sul, durante a pandemia causada pelo COVID-19 através de um questionário online. Foram coletadas informações sobre frequência alimentar, atividade física, número de lanches entre refeições, horas de sono, costume de cozinhar e hábito de fumar antes e durante o período de distanciamento social. As variáveis numéricas foram comparadas com teste t de Student ou Wilcoxon. As variáveis categóricas foram comparadas utilizando-se o teste de McNemar. Participaram da pesquisa 369 gaúchos, sendo 76,8 % do sexo feminino. Em relação ao início da pandemia, os participantes referiram um aumento significativo no consumo de vegetais (p = 0,005) e frutas (p = 0,029) e uma diminuição significativa no consumo de laticínios (p < 0,001), carnes (p = 0,010), doces (p = 0,013) e produtos ultraprocessados (p = 0,008). A média do IMC referido dos participantes também aumentou (p < 0,001), enquanto os dias de práticas de atividade física reduziram (p < 0,001) durante o período de distanciamento social. O estudo mostra que as restrições impostas pela pandemia podem afetar a frequência alimentar e o estilo de vida da população

Pair Production Absorption Troughs in Gamma-Ray Burst Spectra: A Potential Distance Discriminator

Relativistic bulk motion with large Lorentz factors has recently been inferred for gamma-ray bursts regardless of whether they are of galactic or cosmological origin. This conclusion results from calculations of internal pair production transparency in bursts that usually assume an infinite power-law source spectrum for simplicity, an approximation that is quite adequate for some bursts detected by EGRET. However, for a given bulk Lorentz factor \teq{\Gamma}, photons above the EGRET range can potentially interact with sub-MeV photons in such calculations. Hence it is essential to accurately address the spectral curvature in bursts seen by BATSE. In this paper we present the major properties induced in photon-photon opacity considerations by such spectral curvature. The observed spectral breaks around 1 MeV turn out to be irrelevant to opacity in cosmological bursts, but are crucial to estimates of source transparency in the 1 GeV -- 1 TeV range for sources located in the galactic halo. We find that broad absorption troughs can arise at these energies for suitable bulk motion parameters \teq{\Gamma}. Such troughs are probably an unambiguous signature of a galactic halo population, and if observed by experiments such as Whipple, MILAGRO and GLAST, would provide powerful evidence that such bursts are not at cosmological distances.Comment: 10 pages, AASTeX format, including 2 eps figures, ApJLett in pres

Estimating the Importance of Civil Construction for the Brazilian Economy Through Hypothetical Extraction of the Input-Output Matrix

This paper aims to undertake a systemic analysis of civil construction to verify whether public investments made from 2007 onwards were able to increase the sector's productive linkages in the Brazilian economy. For this, the hypothetical extraction method of the input-output matrix and the official matrices of the country from 2005 and 2015 are used. The results show that the importance of the productive structure of the construction sector - total extraction - exceeds 7.42% of GDP in 2005 to 10.06% in 2015. This fact reveals that the civil construction sector in 2005 was the seventh most important moving to the fourth in 2015 in a total of twelve sectors considered. Another important finding lies in the fact that despite the construction sector presenting an increase in the complexity of its productive structure, it showed strong backward linkage, but low forward linkage, in both analyzed periods. Through these results, it is possible to conclude that the tax exemption of some inputs, reduction of real estate interest, expansion of credit for housing through public housing and infrastructure policies may have been essential for the increase in the complexity of the sector's productive chains between the years' from 2005 and 2015. Such findings are useful for the scientific literature that investigates the sector by bringing evidence to Brazil and to policymakers given that possibly the construction sector can be used as a strategy to promote and stimulate economic activity in times of crisis

EGRET Spectral Index and the Low-Energy Peak Position in the Spectral Energy Distribution of EGRET-Detected Blazars

In current theoretical models of the blazar subclass of active galaxies, the broadband emission consists of two components: a low-frequency synchrotron component with a peak in the IR to X-ray band, and a high-frequency inverse Compton component with a peak in the gamma-ray band. In such models, the gamma-ray spectral index should be correlated with the location of the low-energy peak, with flatter gamma-ray spectra expected for blazars with synchrotron peaks at higher photon energies and vice versa. Using the EGRET-detected blazars as a sample, we examine this correlation and possible uncertainties in its construction.Comment: 17 pages including 1 figure, accepted for publication in The Astrophysical Journa

Future of work in the Brazilian Federal District's executive branch

Neste artigo, abordamos o tema ‘Futuro do Trabalho’ com foco no setor público do Distrito Federal brasileiro. O Brasil é uma república federativa e o ente federado em questão possui o oitavo maior PIB entre os 27 entes federados brasileiros (26 estados e o Distrito Federal). Por ser a sede do poder executivo federal, o Distrito Federal apresenta o maior PIB per capita, quase o dobro do vice-campeão, justificando a importância de analisar sua estrutura governamental. Para tanto, reproduzimos o método de Kubota e Maciente (2019) para estimar a tendência de automatizar as ocupações, utilizando o banco de dados de ocupações dos servidores públicos do Distrito Federal. Os resultados mostraram que empregos que exigem níveis mais baixos de escolaridade e envolvem tarefas mais rotineiras são mais propensos à automação. Por fim, com base em nossos resultados, realizamos uma análise estatística descritiva da escolaridade, idade e remuneração dos cargos públicos no Distrito Federal.Revista do Serviço Público - RSP, v. 73, n. 1, 9-31 p.Análise e Ciência de DadosGestão PúblicaISSN Impresso: 0034-9240ISSN Eletrônico: 2357-801

O PROGRAMA BRASILEIRO DE AGRICULTURA FAMILIAR: UMA REVISÃO DE SEUS PRIMEIROS DEZOITO ANOS

O presente artigo realiza uma síntese da literatura acadêmica dos últimos vinte anos relacionada ao Programa Nacional de Fortalecimento da Agricultura Familiar, o PRONAF. O referido programa foi implantado em 1996, com o principal intuito de atender as reivindicações dos atores sociais rurais ligados à agricultura familiar, os quais ressaltavam a importância e urgência da criação de linhas de crédito que suprissem suas necessidades. O trabalho está dividido em Introdução - que apresenta artigos que explicitam o contexto histórico de sua criação e as linhas de crédito com as condições dos financiamentos - em Evolução e Estruturação do Programa - contendo trabalhos que relatam as mudanças que ocorreram ao longo dos anos na sua estruturação - em Focalização e Distribuição dos Recursos - demonstrando artigos que apontam possíveis problemas como a falta de equidade na amplitude do PRONAF em cada estado brasileiro - em Desenvolvimento Econômico e Social - onde são apresentados impactos do programa que foram ressaltados por alguns autores - e por fim, a Conclusão - que retoma os pontos importantes do trabalho

Limits on the GeV Emission from Gamma-Ray Bursts

The Large Area Telescope (LAT) on board of the Fermi satellite detected emission above 30 MeV only in a small fraction of the long gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Burst Monitor (GBM) at 8 keV - 10 MeV. Those bursts that were detected by the LAT were among the brightest GBM bursts. We examine a sample of the most luminous GBM bursts with no LAT detection and obtain upper limits on their high energy fluence. We find an average upper limit of LAT/GBM fluence ratio of 0.13 for GeV fluence during $T_{90}$ and an average upper limit ratio of 0.45 for GeV fluence during the first 600 seconds after the trigger. These ratios strongly constrain various emission models and in particular rule out SSC models for the prompt emission. In about a third of both LAT detected and LAT non-detected bursts, we find that the extrapolation of the MeV range Band spectrum to the GeV range is larger than the observed GeV fluence (or its upper limit). While this excess is not highly significant for any specific burst, the overall excess in a large fraction of the bursts suggests a decline in the high energy spectral slope in at least some of these bursts. Possibly an evidence for the long sought after pair creation limit.Comment: Accepted for publication in MNRA

Search for Sub-TeV Gamma Rays Coincident with BATSE Gamma Ray Bursts

Project GRAND is a 100m x 100m air shower array of proportional wire chambers (PWCs). There are 64 stations each with eight 1.29 m^2 PWC planes arranged in four orthogonal pairs placed vertically above one another to geometrically measure the angles of charged secondaries. A steel plate above the bottom pair of PWCs differentiates muons (which pass undeflected through the steel) from non-penetrating particles. FLUKA Monte Carlo studies show that a TeV gamma ray striking the atmosphere at normal incidence produces 0.23 muons which reach ground level where their angles and identities are measured. Thus, paradoxically, secondary muons are used as a signature for gamma ray primaries. The data are examined for possible angular and time coincidences with eight gamma ray bursts (GRBs) detected by BATSE. Seven of the GRBs were selected because of their good acceptance by GRAND and high BATSE Fluence. The eighth GRB was added due to its possible coincident detection by Milagrito. For each of the eight candidate GRBs, the number of excess counts during the BATSE T90 time interval and within plus or minus five degrees of BATSE's direction was obtained. The highest statistical significance reported in this paper (2.7 sigma) is for the event that was predicted to be the most likely to be observed (GRB 971110).Comment: To be presented at the XXVIII International Cosmic Ray Conference, Tsukuba, Japa