The Blazar Sequence: Validity and Predictions

The "blazar sequence" posits that the most powerful BL Lacertae objects and flat-spectrum radio quasars should have relatively small synchrotron peak frequencies, nu_peak, and that the least powerful such objects should have the highest nu_peak values. This would have strong implications for our understanding of jet formation and physics and the possible detection of powerful, moderately high-redshift TeV blazars. I review the validity of the blazar sequence by using the results of very recent surveys and compare its detailed predictions against observational data. I find that the blazar sequence in its simplest form is ruled out. However, powerful flat-spectrum radio quasars appear not to reach the nu_peak typical of BL Lacs. This could indeed be related to some sort of sequence, although it cannot be excluded that it is instead due to a selection effect.Comment: 9 pages, 4 figures, invited talk at the Workshop "The Multi-messenger approach to high energy gamma-ray sources", Barcelona, Spain, July 4-7, 2006, to appear in the proceeding

Mosaico de imagens de satélite do Pantanal no ano 2000.

O Pantanal devido a sua extensão e dificuldade de acesso representa um desafio para o desenvolvimento de atividades de produção e conservação da natureza. Nesse sentido as tecnologias de Sensoriamento Remoto podem contribuir muito para o conhecimento e manejo desse ecossistema. O presente trabalho apresenta o mosaico de imagens Landsat 7 ETM do ano 2000 do Pantanal, onde ao contrário dos demais produtos dessa natureza, apresenta uma maior precisão de posicionamento em função de um extenso trabalho de campo realizado para o georreferenciamento das imagens. Esse trabalho é o resultado da parceria entre a Embrapa Pantanal e a WWF Brasil e está disponível também na homepage da Embrapa Pantanal. Esperamos com essa iniciativa estar cumprindo com nosso objetivo de levar à comunidade informações sobre o Pantanal.bitstream/item/81191/1/DOC43.pd

A inundação no rio Taquari.

bitstream/CPAP-2009-09/56868/1/FOL131.pd

Why is CDMA the solution for mobile satellite communication

It is demonstrated that spread spectrum Code Division Multiple Access (CDMA) systems provide an economically superior solution to satellite mobile communications by increasing the system maximum capacity with respect to single channel per carrier Frequency Division Multiple Access (FDMA) systems. Following the comparative analysis of CDMA and FDMA systems, the design of a model that was developed to test the feasibility of the approach and the performance of a spread spectrum system in a mobile environment. Results of extensive computer simulations as well as laboratory and field tests results are presented

The number counts, luminosity functions and evolution of microwave-selected (WMAP) blazars and radio galaxies

(Abridged) We carried out an extensive search to identify the counterparts of all the sources listed in the WMAP 3-yr catalogue using literature and archival data. Our work led to the identification of 309 WMAP sources, 98% of which are blazars, radio quasars or radio galaxies. At present, 15 objects still remain without identification due to the lack of optical spectroscopic data or a clear radio counterpart. Our results allow us to define a flux limited sample of 203 high Galactic latitude microwave sources ($f_{41GHz} \ge 1$ Jy, $|b_{\rm II}| > 15^\circ$) which is virtually completely identified (99%). The microwave band is ideally suited for blazar statistical studies since this is the part of the em spectrum that is least affected by the superposition of spectral components of different origin. Using this data-set we derived number counts, luminosity functions and cosmological evolution of blazars and radio galaxies at microwave frequencies. Our results are in good agreement with those found at radio frequencies. The 5 GHz bivariate blazar luminosity functions are similar to those derived from the DXRBS survey, which shows that this sample is representative of the blazar population at 41 GHz. Microwave selected broad- lined quasars are about 6 times more abundant than BL Lacs, a ratio that is similar to, or larger than, that seen at radio and gamma-ray frequencies, once spectral selection effects are taken into account. This strongly suggests that the mechanism responsible for the generation of gamma-rays is, at first order, the same in all blazar types. Our results confirm the findings of Giommi & Colafrancesco (2004, 2006) that blazars and radio galaxies are the largest contaminants of the CMB anisotropy maps. We predict that these sources are also bright gamma-ray sources, most of which will be detected by AGILE and FERMI.Comment: 18 pages, 11 figures, 3 tables. A&A in pres

X-Ray Spectral Variability of PKS 2005-489 During the Spectacular November 1998 Flare

We report on monitoring of the BL Lac object PKS 2005-489 by the Rossi X-ray Timing Explorer (RXTE) in October-December 1998. During these months, the source underwent a spectacular flare; at its peak on November 10, its 2-10 keV flux was $3.33 \times 10^{-10} {\rm ~erg ~cm^{-2} ~s^{-1}}$, over 30 times brighter than in quiescence. During the rising phase, the X-ray spectrum of PKS 2005-489 hardened considerably, reaching $\alpha = 1.32~ (F_\nu \propto \nu^{-\alpha})$ near maximum. During the declining phase, the X-ray spectrum steepened rapidly, reaching $\alpha = 1.82$, then became somewhat harder towards the end of December ($\alpha \sim 1.6$). While such behavior has been seen before, the simplicity, magnitude and duration of this flare allowed us to study it in great detail. We argue that this flare was caused by either the injection of particles into the jet or {\it in situ} particle acceleration, and that the spectral steepening which followed the flare maximum was the result of synchrotron cooling. Contrary to other recently observed blazar flares (e.g., Mkn 501, 3C 279, PKS 2155-304), our results do not imply a major shift in the location of the synchrotron peak during this flare.Comment: ApJ Letters in press, 6 pages, 2 figures Corrected reference