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We present the first catalog of high-confidence gamma-ray sources detected by the AGILE satellite during observations performed from July 9, 2007 to June 30, 2008. Catalogued sources are detected by merging all the available data over the entire time period. AGILE, launched in April 2007, is an ASI mission devoted to gamma-ray observations in the 30 MeV - 50 GeV energy range, with simultaneous X-ray imaging capability in the 18-60 keV band. This catalog is based on Gamma-Ray Imaging Detector (GRID) data for energies greater than 100 MeV. For the first AGILE catalog we adopted a conservative analysis, with a high-quality event filter optimized to select gamma-ray events within the central zone of the instrument Field of View (radius of 40 degrees). This is a significance-limited (4 sigma) catalog, and it is not a complete flux-limited sample due to the non-uniform first year AGILE sky coverage. The catalog includes 47 sources, 21 of which are associated with confirmed or candidate pulsars, 13 with Blazars (7 FSRQ, 4 BL Lacs, 2 unknown type), 2 with HMXRBs, 2 with SNRs, 1 with a colliding-wind binary system, 8 with unidentified sources.
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Aims. We present the second AGILE-GRID Catalog (2AGL) of {gamma}-ray sources in the 100 MeV-10 GeV energy range. Methods. With respect to previous AGILE-GRID catalogs, the current 2AGL Catalog is based on the first 2.3 years of science data from the AGILE mission (the so called pointing mode) and incorporates more data and several analysis improvements, including better calibrations at the event reconstruction level, an updated model for the Galactic diffuse gamma-ray emission, a refined procedure for point-like source detection, and the inclusion of a search for extended {gamma}-ray sources. Results. The 2AGL Catalog includes 175 high-confidence sources (above 4{sigma} significance) with their location regions and spectral properties, and a variability analysis with 4-day light curves for the most significant ones. Relying on the error region of each source position, including systematic uncertainties, 121 sources are considered as positionally associated with known couterparts at different wavelengths or detected by other {gamma}-ray instruments. Among the identified or associated sources, 62 are Active Galactic Nuclei (AGNs) of the blazar class. Pulsars represent the largest Galactic source class, with 40 associated pulsars, 7 of them with detected pulsation; 8 Supernova Remnants and 4 high-mass X-ray binaries have also been identified. A substantial number of 2AGL sources are unidentified: for 54 sources no known counterpart is found at different wavelengths. Among these sources, we discuss a sub-class of 29 AGILE-GRID-only {gamma}-ray sources that are not present in 1FGL, 2FGL or 3FGL catalogs; the remaining sources are unidentified in both 2AGL and 3FGL Catalogs. We also present an extension of the analysis of 2AGL sources detected in the 50-100 MeV energy range.
We present a new catalog of TeV gamma-ray sources using 1523 days of data from the High Altitude Water Cherenkov (HAWC) observatory. The catalog represents the most sensitive survey of the Northern gamma-ray sky at energies above several TeV, with three times the exposure compared to the previous HAWC catalog, 2HWC. We report 65 sources detected at $geq$ 5 sigma significance, along with the positions and spectral fits for each source. The catalog contains eight sources that have no counterpart in the 2HWC catalog, but are within $1^circ$ of previously detected TeV emitters, and twenty sources that are more than $1^circ$ away from any previously detected TeV source. Of these twenty new sources, fourteen have a potential counterpart in the fourth textit{Fermi} Large Area Telescope catalog of gamma-ray sources. We also explore potential associations of 3HWC sources with pulsars in the ATNF pulsar catalog and supernova remnants in the Galactic supernova remnant catalog.
The origin of cosmic neutrinos is still largely unknown. Using data obtained by the gamma-ray imager on board of the AGILE satellite, we systematically searched for transient gamma-ray sources above 100 MeV that are temporally and spatially coincident with ten recent high-energy neutrino IceCube events. We find three AGILE candidate sources that can be considered possible counterparts to neutrino events. Detecting 3 gamma-ray/neutrino associations out of 10 IceCube events is shown to be unlikely due to a chance coincidence. One of the sources is related to the BL Lac source TXS 0506+056. For the other two AGILE gamma-ray sources there are no obvious known counterparts, and both Galactic and extragalactic origin should be considered.
In three years of observations since the beginning of nominal science operations in August 2008, the Large Area Telescope (LAT) on board the Fermi Gamma Ray Space Telescope has observed high-energy (>20 MeV) gamma-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above ~ 20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared to emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.
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