ISDC Science Results
The high energy spectrum of 3C 273
2015-03-12 | AGN, INTEGRAL, Fermi
We studied the high energy spectral variability of the bright quasar 3C 273 from ~1 keV up to ~10 GeV using data collected with RXTE-PCA, INTEGRAL and Fermi/LAT and compared them with radio data at 37 GHz collected at the Metsähovi Radio Observatory. Quasi-simultaneous broad band high energy spectra have been built at the epoch of γ ray flares and X-ray flares. Both timing and spectral analysis suggest a two-component scenario, where the X-ray emission is likely dominated by a Seyfert-like component, while the γ ray emission is dominated by a blazar-like component originated in the relativistic jet.
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Probing the cosmic-ray content of galaxy clusters by stacking Fermi-LAT count maps
2013-10-02 | Fermi, VHE, Galaxy cluster
The cosmic-ray content of galaxy clusters is expected to produce a gamma-ray signal that could be detected by the Fermi Gamma-ray Space Telescope. We show here that even by stacking the Fermi observations at the position of 53 known galaxy clusters we still cannot detect such an emission.
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A stacking method to study the gamma-ray emission of source samples based on the co-adding of Fermi LAT count maps
2012-09-13 | Fermi, VHE
Objects with low integrated gamma-ray fluxes that are not detected individually may become detectable when their corresponding count maps are added. This paper describes a method that can be used to analyze stacked data obtained with the Fermi Large Area Telescope.
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Fermi/LAT observations of 1ES 0229+200: implications for extragalactic magnetic fields and background light
2012-01-25 | Fermi, VHE
New data from the Fermi/LAT instrument allow us to measure the GeV spectrum of a prominent TeV blazar 1ES 0229+200. Being one of the hardest TeV sources on the sky, 1ES 0229+200 provides the best constraints for the Extragalactic magnetic field and Extragalactic background light. The new observations permit us to measure these two quantities simultaneously.
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Search for high energy γ-ray emission from galaxies of the Local Group with Fermi/LAT
2011-09-19 | Fermi
High-energy γ-ray emission is searched for in galaxies from the Local Group using Fermi/LAT. No significant signal is found in the data, however the study shows imminent detection is expected from M 33 and M 83.
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12 hours spikes from the Crab Pevatron
2010-12-15 | INTEGRAL, Fermi, VHE | Press Release
The Crab nebula featured 3 gamma-ray spikes in the GeV band in September 2010. These γ-ray flares are due to synchrotron emission from a very compact Pevatron located closer to the pulsar than the equatorial termination shock between the supersonic wind and the surrounding nebula. The spectral and timing properties of the flare are interpreted in the framework of a relativistically moving emitter. The flare duration is of the order of the synchrotron cooling time scale for electrons at an energy larger than 1015 eV, the highest electron energy ever measured in a cosmic accelerator.
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Eta Carinae: a very large hadron collider
2010-12-13 | Fermi, INTEGRAL | Press Release
Eta Carinae system consists of two massive stars with dense supersonic winds. Observation with Fermi/LAT suggests that collisions of high energetic hadrons take place in the colliding winds region.
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Seyfert 2 galaxies in the GeV band: jets and starburst
2010-10-18 | Fermi, AGN, INTEGRAL
We present Fermi/LAT data analysis of two unusual suspects in the GeV band, NGC 1068 and NGC 4945, which are both composite starburst/active galactic nuclei objects. We show that the GeV emission of NGC 4945 could be interpreted in terms of starburst activity, while the one of NGC 1068 should account for a dominant contribution from the central AGN.
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HESS J1632-478: An Energetic Relic
2010-07-04 | VHE, Fermi
The unidentified very high energy source HESS J1632-478 is very likely an old (104 years) Pulsar Wind Nebula with a size of several parsecs containing very high energy electrons cooling slowly mostly through Inverse Compton scattering. Its spectrum is made of a faint synchrotron component (from the radio to the X-rays) emitted by electrons accelerated up to very high energies and of a bright high-energy gamma-ray component emitted by inverse Compton scatering against infrared photons.
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Evidence for strong extragalactic magnetic fields from Fermi observations of TeV blazars
2010-04-04 | Fermi, AGN, VHE | Press Release
FERMI/LAT observations of distant blazars together with theoretical modeling provide us with the first clue about the parameters of primordial magnetic field, survived up to nowadays in the voids of the Large-Scale Structure.
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