Insights into the high-energy γ-ray emission of Markarian 501 from extensive multifrequency observations in the Fermi era

We report on the γ-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) γ-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 ± 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 ± 0.14, and the softest one is 2.51 ± 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size ≲0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (≃1044 erg s-1) constitutes only a small fraction (∼10-3) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude. © 2011. The American Astronomical Society

Influência dos níveis de concentrado sobre os cortes comerciais, os constituintes não-carcaça e os componentes da perna de cordeiros confinados Effect of concentrate levels on retail cuts, non-carcass and leg components of crossbred feedlot lambs

Um experimento foi realizado com o objetivo de determinar a influência dos níveis de concentrado sobre o peso e o rendimento dos cortes e dos constituintes não-carcaça e a composição tecidual da perna de cordeiros mestiços de Dorper terminados em confinamento ou mestiços de Dorper x Santa Inês. Foram utilizados 32 cordeiros (não-castrados) ½ Dorper x ½ Santa Inês (peso médio inicial de 17,1 kg) alimentados com dietas contendo 30, 45, 60 e 75% de concentrado. Os cordeiros foram distribuídos em um delineamento inteiramente casualizado com quatro tratamentos e oito repetições. Os animais foram mantidos em confinamento durante 43 dias. Após o abate, as carcaças foram resfriadas por 24 horas. Foram registrados os pesos e as porcentagens dos cortes da meia-carcaça e as porcentagens de osso, músculos e tecido adiposo, avaliadas por meio de dissecação da perna. Houve efeito significativo linear crescente dos níveis de concentrado sobre os pesos de pescoço, paleta, costilhar, lombo e perna. Verificou-se também efeito significativo linear decrescente sobre os rendimentos dos cortes comerciais (pescoço, perna e paleta), excetuando-se o de costilhar, que cresceu linearmente. A espessura de gordura e a área de olho-de-lombo foram influenciadas pelos níveis de concentrado. Observou-se efeito significativo sobre os constituintes não-carcaça, exceto o trato digestório, que não foi afetado pelos níveis de concentrado. O aumento do nível de concentrado influenciou o peso e o rendimento dos cortes e órgãos internos e aumentou a proporção e a deposição de gordura na carcaça.<br>Thirty-two intact lambs averaging 17.1 kg of initial body weight were assigned to one of the following four treatments: 30, 45, 60 or 75% of dietary concentrate in a completely randomized design (eight lambs/treatment). Lambs were feedlot fed during the experimental period (43 days). After slaughter, carcasses were refrigerated for 24 h. It was measured the weights and percentages of five cuts from the half carcass as well as the proportion of muscle, bone and fat tissue from the leg. The weights of neck, shoulder, ribs, loin and leg all increased linearly by increasing the level of concentrate in the diet while the opposite was observed for the yields of neck, leg, and shoulder; yield of ribs followed the increment of concentrate in the diet and increased linearly. Fat thickness and loin eye area were both affected by the level of concentrate in the diet. The same was observed for the non-carcass components with the exception of digestive tract. Feeding increasing dietary levels of concentrate to lambs affected the weight and yield of retail cuts and internal organs and increased the proportion and deposition of fat in the carcass