Catálogo de publicaciones - revistas

<jats:title>ABSTRACT</jats:title> <jats:p>We report on 18 months of multiwavelength observations of the blazar 3C 454.3 (<jats:italic>Crazy Diamond</jats:italic>) carried out in the period 2007 July–2009 January. In particular, we show the results of the <jats:italic>AGILE</jats:italic> campaigns which took place on 2008 May–June, 2008 July–August, and 2008 October–2009 January. During the 2008 May–2009 January period, the source average flux was highly variable, with a clear fading trend toward the end of the period, from an average γ-ray flux <jats:italic>F</jats:italic> <jats:sub>E&gt;100 MeV</jats:sub> ≳ 200 × 10<jats:sup>−8</jats:sup> photons cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>  in 2008 May–June, to <jats:italic>F</jats:italic> <jats:sub>E&gt;100 MeV</jats:sub> ∼ 80 × 10<jats:sup>−8</jats:sup> photons cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>  in 2008 October–2009 January. The average γ-ray spectrum between 100 MeV and 1 GeV can be fit by a simple power law, showing a moderate softening (from Γ<jats:sub>GRID</jats:sub> ∼ 2.0 to Γ<jats:sub>GRID</jats:sub> ∼ 2.2) toward the end of the observing campaign. Only 3σ upper limits can be derived in the 20–60 keV energy band with Super-<jats:italic>AGILE</jats:italic>, because the source was considerably off-axis during the whole time period. In 2007 July–August and 2008 May–June, 3C 454.3 was monitored by <jats:italic>Rossi X-ray Timing Explorer</jats:italic> (<jats:italic>RXTE</jats:italic>). The <jats:italic>RXTE</jats:italic>/Proportional Counter Array (PCA) light curve in the 3–20 keV energy band shows variability correlated with the γ-ray one. The <jats:italic>RXTE</jats:italic>/PCA average flux during the two time periods is <jats:italic>F</jats:italic> <jats:sub>3-20 keV</jats:sub> = 8.4 × 10<jats:sup>−11</jats:sup> erg cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>, and <jats:italic>F</jats:italic> <jats:sub>3-20 keV</jats:sub> = 4.5 × 10<jats:sup>−11</jats:sup> erg cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>, respectively, while the spectrum (a power law with photon index Γ<jats:sub>PCA</jats:sub> = 1.65 ± 0.02) does not show any significant variability. Consistent results are obtained with the analysis of the <jats:italic>RXTE</jats:italic>/High-Energy X-Ray Timing Experiment quasi-simultaneous data. We also carried out simultaneous <jats:italic>Swift</jats:italic> observations during all <jats:italic>AGILE</jats:italic> campaigns. <jats:italic>Swift</jats:italic>/XRT detected 3C 454.3 with an observed flux in the 2–10 keV energy band in the range (0.9–7.5) × 10<jats:sup>−11</jats:sup> erg cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup> and a photon index in the range Γ<jats:sub>XRT</jats:sub> = 1.33–2.04. In the 15–150 keV energy band, when detected, the source has an average flux of about 5 mCrab. GASP-WEBT monitored 3C 454.3 during the whole 2007–2008 period in the radio, millimeter, near-IR, and optical bands. The observations show an extremely variable behavior at all frequencies, with flux peaks almost simultaneous with those at higher energies. A correlation analysis between the optical and the γ-ray fluxes shows that the γ-optical correlation occurs with a time lag of τ = −0.4<jats:sup>+0.6</jats:sup> <jats:sub>−0.8</jats:sub> days, consistent with previous findings for this source. An analysis of 15 GHz and 43 GHz VLBI core radio flux observations in the period 2007 July–2009 February shows an increasing trend of the core radio flux, anti-correlated with the higher frequency data, allowing us to derive the value of the source magnetic field. Finally, the modeling of the broadband spectral energy distributions for the still unpublished data, and the behavior of the long-term light curves in different energy bands, allow us to compare the jet properties during different emission states, and to study the geometrical properties of the jet on a time-span longer than one year.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>We report observation of the supernova remnant (SNR) IC 443 (G189.1+3.0) with the <jats:italic>Fermi Gamma-ray Space Telescope</jats:italic> Large Area Telescope (LAT) in the energy band between 200 MeV and 50 GeV. IC 443 is a shell-type SNR with mixed morphology located off the outer Galactic plane where high-energy emission has been detected in the X-ray, GeV and TeV gamma-ray bands. Past observations suggest IC 443 has been interacting with surrounding interstellar matter. Proximity between dense shocked molecular clouds and GeV–TeV gamma-ray emission regions detected by <jats:italic>EGRET</jats:italic>, <jats:italic>MAGIC</jats:italic>, and <jats:italic>VERITAS</jats:italic> suggests an interpretation that cosmic-ray (CR) particles are accelerated by the SNR. With the high gamma-ray statistics and broad energy coverage provided by the LAT, we accurately characterize the gamma-ray emission produced by the CRs accelerated at IC 443. The emission region is extended in the energy band with θ<jats:sub>68</jats:sub> = 0.°27 ± 0.°01(stat) ± 0.°03(sys) for an assumed two-dimensional Gaussian profile and overlaps almost completely with the extended source region of <jats:italic>VERITAS</jats:italic>. Its centroid is displaced significantly from the known pulsar wind nebula (PWN) which suggests the PWN is not the major contributor in the present energy band. The observed spectrum changes its power-law slope continuously and continues smoothly to the <jats:italic>MAGIC</jats:italic> and <jats:italic>VERITAS</jats:italic> data points. The combined gamma-ray spectrum (200 MeV &lt;<jats:italic>E</jats:italic>&lt; 2 TeV) is reproduced well by decays of neutral pions produced by a broken power-law proton spectrum with a break around 70 GeV.</jats:p>