F. Longo

ORCID: 0000-0003-2501-2270
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About
Contact & Profiles
Research Areas
  • Gamma-ray bursts and supernovae
  • Astrophysics and Cosmic Phenomena
  • Particle Detector Development and Performance
  • Dark Matter and Cosmic Phenomena
  • Radio Astronomy Observations and Technology
  • Pulsars and Gravitational Waves Research
  • Astrophysical Phenomena and Observations
  • Astronomical Observations and Instrumentation
  • Solar and Space Plasma Dynamics
  • Geophysics and Gravity Measurements
  • Neutrino Physics Research
  • SAS software applications and methods
  • Astronomy and Astrophysical Research
  • Particle Accelerators and Free-Electron Lasers
  • Nuclear Physics and Applications
  • Particle physics theoretical and experimental studies
  • Astro and Planetary Science
  • Radiation Detection and Scintillator Technologies
  • Ionosphere and magnetosphere dynamics
  • Cosmology and Gravitation Theories
  • Radiation Therapy and Dosimetry
  • Galaxies: Formation, Evolution, Phenomena
  • Advanced Radiotherapy Techniques
  • Medical Imaging Techniques and Applications
  • Stellar, planetary, and galactic studies

Istituto Nazionale di Fisica Nucleare, Sezione di Trieste
2016-2025

University of Trieste
2016-2025

University of Udine
2015-2024

Universitat de Barcelona
2021-2024

Institut d'Estudis Espacials de Catalunya
2024

Istituto Nazionale di Fisica Nucleare
2007-2023

Université Paris-Saclay
2019-2023

Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2019-2023

CEA Paris-Saclay
2019-2023

Centre National de la Recherche Scientifique
2013-2023

Geant4 is a software toolkit for the simulation of passage particles through matter. It used by large number experiments and projects in variety application domains, including high energy physics, astrophysics space science, medical physics radiation protection. Its functionality modeling capabilities continue to be extended, while its performance enhanced. An overview recent developments diverse areas presented. These include optimization complex setups; improvements propagation fields; new...

10.1109/tns.2006.869826 article EN IEEE Transactions on Nuclear Science 2006-02-01

Geant4 is a software toolkit for the simulation of passage particles through matter. It used by large number experiments and projects in variety application domains, including high energy physics, astrophysics space science, medical physics radiation protection. Over past several years, major changes have been made to order accommodate needs these user communities, efficiently exploit growth computing power available advances technology. The adaptation multithreading, detector modeling...

10.1016/j.nima.2016.06.125 article EN cc-by Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 2016-07-02

We present the third Fermi Large Area Telescope (LAT) source catalog (3FGL) of sources in 100 MeV–300 GeV range. Based on first 4 yr science data from Gamma-ray Space mission, it is deepest yet this energy Relative to Second LAT catalog, 3FGL incorporates twice as much data, well a number analysis improvements, including improved calibrations at event reconstruction level, an updated model for Galactic diffuse γ-ray emission, refined procedure detection, and methods associating with...

10.1088/0067-0049/218/2/23 article EN The Astrophysical Journal Supplement Series 2015-06-12

We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on first eight years science data from Gamma-ray Space mission in energy range 50 MeV to 1 TeV, it is deepest yet this range. Relative 3FGL catalog, 4FGL has twice as much exposure well a number analysis improvements, including an updated model for Galactic diffuse emission, and two sets light curves (1-year 2-month intervals). The includes 5064 sources above 4 sigma significance, which we provide...

10.3847/1538-4365/ab6bcb article EN The Astrophysical Journal Supplement Series 2020-03-10

The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some most dark matter (DM) dominated objects known. We report on gamma-ray observations dSphs based 6 years Fermi Large Area Telescope data processed with new Pass 8 event-level analysis. None significantly detected in gamma rays, and we present upper limits DM annihilation cross section from a combined analysis 15 dSphs. These constraints among strongest robust to date lie below canonical thermal relic for mass $\lesssim$...

10.1103/physrevlett.115.231301 article EN publisher-specific-oa Physical Review Letters 2015-11-30

The γ-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, a residual all-sky component commonly called isotropic background (IGRB). IGRB comprises all extragalactic emissions too faint or resolved in given survey, as well any foregrounds that are approximately isotropic. first measurement Large Area Telescope (LAT) on board Fermi Gamma-ray Space (Fermi) used 10 months sky-survey...

10.1088/0004-637x/799/1/86 article EN The Astrophysical Journal 2015-01-19

The gamma-ray sky >100 MeV is dominated by the diffuse emissions from interactions of cosmic rays with interstellar gas and radiation fields Milky Way. Observations these provide a tool to study cosmic-ray origin propagation, medium. We present measurements first 21 months Fermi-LAT mission compare models emission generated using GALPROP code. are fitted data incorporate astrophysical input for distribution sources, fields. To assess uncertainties associated input, grid created varying...

10.1088/0004-637x/750/1/3 article EN The Astrophysical Journal 2012-04-06

The second catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (LAT) in two years scientific operation is presented. LAT AGN (2LAC) includes 1017 γ-ray sources located at high Galactic latitudes (|b| > 10°) that are with a test statistic (TS) greater than 25 and associated statistically AGNs. However, some these affected analysis issues multiple Consequently, we define Clean Sample which 886 AGNs, comprising 395 BL Lacertae objects (BL Lac objects), 310...

10.1088/0004-637x/743/2/171 article EN The Astrophysical Journal 2011-12-02

We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because instrument does not have an onboard magnet, we distinguish two species by exploiting Earth's shadow, which is offset in opposite directions for charges due to magnetic field. estimate subtract proton background using different methods that produce consistent results. report electron-only spectrum, positron-only fraction between 20 GeV 200 GeV. confirm rises energy 20-100 range. The...

10.1103/physrevlett.108.011103 article EN publisher-specific-oa Physical Review Letters 2012-01-05

The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It based on (3FGL) sources between 100 MeV and 300 GeV with a Test Statistic (TS) greater than 25, 2008 August 4 2012 July 31. 3LAC includes 1591 AGNs located at high Galactic latitudes (|b|>10{\deg}), 71% increase over second 2 years data. There are 28 duplicate associations, thus 1563 2192 high-latitude gamma-ray 3FGL AGNs. Most them (98%) blazars. About half newly blazars unknown type, i.e.,...

10.1088/0004-637x/810/1/14 article EN The Astrophysical Journal 2015-08-25

Satellite galaxies of the Milky Way are among most promising targets for dark matter searches in gamma rays. We present a search consisting weakly interacting massive particles, applying joint likelihood analysis to 10 satellite with 24 months data Fermi Large Area Telescope. No signal is detected. Including uncertainty distribution, robust upper limits placed on annihilation cross sections. The 95% confidence level range from about 10(-26) cm3 s(-1) at 5 GeV 5×10(-23) 1 TeV, depending final...

10.1103/physrevlett.107.241302 article EN publisher-specific-oa Physical Review Letters 2011-12-08

We report on the first Fermi Large Area Telescope (LAT) measurements of so-called "extragalactic" diffuse gamma-ray emission (EGB). This component is generally considered to have an isotropic or nearly distribution sky with diverse contributions discussed in literature. The derivation EGB based detailed modeling bright foreground Galactic emission, detected LAT sources, and solar emission. find spectrum consistent a power law differential spectral index gamma = 2.41 +/- 0.05 intensity I(>100...

10.1103/physrevlett.104.101101 article EN Physical Review Letters 2010-03-08

The blazar Mrk 501 was observed at energies above 0.10 TeV with the MAGIC Telescope from 2005 May through July. high sensitivity of instrument enabled determination flux and spectrum source on a night-by-night basis. Throughout our observational campaign, found to vary by an order magnitude. Intranight variability flux-doubling times down 2 minutes during two most active nights, namely, June 30 July 9. These are fastest variations ever in 501. ~20 minute long flare 9 showed indication 4 ± 1...

10.1086/521382 article EN The Astrophysical Journal 2007-11-10

The dwarf spheroidal satellite galaxies of the Milky Way are some most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack astrophysical backgrounds, widely considered be among promising targets for indirect detection via $\ensuremath{\gamma}$ rays. Here we report on $\ensuremath{\gamma}$-ray observations 25 based 4 years Fermi Large Area Telescope (LAT) data. None significantly detected in rays, present flux upper limits between 500 MeV GeV. We...

10.1103/physrevd.89.042001 article EN Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology 2014-02-11

The Fermi Large Area Telescope (Fermi-LAT, hereafter LAT), the primary instrument on Gamma-ray Space (Fermi) mission, is an imaging, wide field-of-view, high-energy γ-ray telescope, covering energy range from 20 MeV to more than 300 GeV. During first years of LAT team has gained considerable insight into in-flight performance instrument. Accordingly, we have updated analysis used reduce data for public release as well response functions (IRFs), description provided analysis. In this paper,...

10.1088/0067-0049/203/1/4 article EN The Astrophysical Journal Supplement Series 2012-10-12

The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from giant flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C 279, at distance more than 5 billion light-years (a redshift 0.536). No quasar been observed previously in radiation, and this is also most object emitting above 50 gigaelectron volts. Because high-energy may be stopped by interacting with diffuse background light universe,...

10.1126/science.1157087 article EN Science 2008-06-26

Microquasars are binary star systems with relativistic radio-emitting jets. They potential sources of cosmic rays and can be used to elucidate the physics We report detection variable gamma-ray emission above 100 gigaelectron volts from microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar phase, which suggests that is periodic. The strongest not observed when two stars closest one another, implying strong modulation or absorption processes.

10.1126/science.1128177 article EN Science 2006-05-19

The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of emission towards Galactic centre (GC) in high-energy gamma-rays. This paper describes analysis data taken during first 62 months mission energy range 1-100 GeV from a $15^\circ \times 15^\circ$ region about direction GC, and implications for interstellar emissions produced by cosmic ray (CR) particles interacting with gas radiation fields inner Galaxy point sources detected. Specialised models (IEMs) are...

10.3847/0004-637x/819/1/44 article EN The Astrophysical Journal 2016-02-26

Abstract The region around the Galactic Center (GC) is now well established to be brighter at energies of a few GeV than what expected from conventional models diffuse gamma-ray emission and catalogs known sources. We study excess using 6.5 yr data Fermi Large Area Telescope. characterize uncertainty GC spectrum morphology due uncertainties in cosmic-ray source distributions propagation, distribution interstellar gas Milky Way, potential contribution bubbles. also evaluate properties...

10.3847/1538-4357/aa6cab article EN The Astrophysical Journal 2017-05-01

We present an incremental version (4FGL-DR3, for Data Release 3) of the fourth Fermi-LAT catalog gamma-ray sources. Based on first twelve years science data in energy range from 50 MeV to 1 TeV, it contains 6658 The analysis improves that used 4FGL over eight data: more sources are fit with curved spectra, we introduce a robust spectral parameterization pulsars, and extend points TeV. parameters, distributions, associations updated all Light curves rebuilt yr intervals (not 2 month...

10.3847/1538-4365/ac6751 article EN cc-by The Astrophysical Journal Supplement Series 2022-06-01

<i>Context. <i/> AGILE is an Italian Space Agency mission dedicated to observing the gamma-ray Universe. The AGILE's very innovative instrumentation for first time combines a imager (sensitive in energy range 30 MeV–50 GeV), hard X-ray 18–60 keV), calorimeter 350 keV–100 MeV), and anticoincidence system. was successfully launched on 2007 April 23 from Indian base of Sriharikota inserted equatorial orbit with low particle background.<i>Aims. <i/>AGILE provides crucial data study active...

10.1051/0004-6361/200810527 article EN Astronomy and Astrophysics 2009-01-30

A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by Large Area Telescope on board Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 lasted approximately 16 days. second was September 2010 4 During these outbursts, flux nebula increased factors of four six, respectively. brevity implies that gamma rays were emitted via...

10.1126/science.1199705 article EN Science 2011-01-07

Recent detections of the starburst galaxies M82 and NGC 253 by gamma-ray telescopes suggest that rapidly forming massive stars are more luminous at energies compared to their quiescent relatives. Building upon those results, we examine a sample 69 dwarf, spiral, ultraluminous infrared photon 0.1–100 GeV using 3 years data collected Large Area Telescope (LAT) on Fermi Gamma-ray Space (Fermi). Measured fluxes from significantly detected sources flux upper limits for remaining used explore...

10.1088/0004-637x/755/2/164 article EN The Astrophysical Journal 2012-08-07
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