M. Orienti
A5035543291- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Neutrino Physics Research
- Particle Detector Development and Performance
- Particle Accelerators and Free-Electron Lasers
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Particle physics theoretical and experimental studies
- Astrophysics and Star Formation Studies
- Solar and Space Plasma Dynamics
- Nuclear Physics and Applications
- Geophysics and Gravity Measurements
- Particle accelerators and beam dynamics
- Gyrotron and Vacuum Electronics Research
- Astro and Planetary Science
- Superconducting and THz Device Technology
- GNSS positioning and interference
- Computational Physics and Python Applications
- Stellar, planetary, and galactic studies
- Cosmology and Gravitation Theories
Istituto di Radioastronomia di Bologna
2015-2024
University of Turku
2021-2023
National Institute for Astrophysics
2011-2023
University of Łódź
2021-2023
Niels Brock
2023
University of Copenhagen
2023
Main Astronomical Observatory
2023
Taras Shevchenko National University of Kyiv
2023
National Academy of Sciences of Ukraine
2023
Georgia Institute of Technology
2023
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 $\lesssim$...
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...
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...
Dark matter in the Milky Way may annihilate directly into gamma rays, producing a monoenergetic spectral line. Therefore, detecting such signature would be strong evidence for dark annihilation or decay. We search lines Fermi Large Area Telescope observations of halo energy range 200 MeV to 500 GeV using analysis methods from our most recent line searches. The main improvements relative previous works are use 5.8 years data reprocessed with Pass 8 event-level and additional resulting...
We present a catalog of sources detected above 10 GeV by the Fermi Large Area Telescope (LAT) in first 7 years data using Pass 8 event-level analysis. This is Third Catalog Hard Fermi-LAT Sources (3FHL), containing 1556 objects characterized - 2 TeV energy range. The sensitivity and angular resolution are improved factors 3 relative to previous LAT at same energies (1FHL). vast majority (79%) associated with extragalactic counterparts other wavelengths, including 16 located very high...
The Fermi bubbles are two large structures in the gamma-ray sky extending to 55° above and below Galactic center. We analyze 50 months of Large Area Telescope data between 100 MeV 500 GeV 10° latitude derive spectrum morphology bubbles. thoroughly explore systematic uncertainties that arise when modeling diffuse emission through separate approaches. is well described by either a log parabola or power law with an exponential cutoff. exclude simple more than 7σ significance. cutoff has index...
The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area (4LAC) between 2008 August 4 and 2016 2 contains 2863 objects located at high Galactic latitudes (|b|>10{\deg}). It includes 85% more sources than previous 3LAC based on years data. AGNs represent least 79% high-latitude in Fermi-Large Source Catalog (4FGL), which covers energy range from 50 MeV to 1 TeV. In addition, 344 gamma-ray are found low latitudes. Most 4LAC blazars (98%),...
The light emitted by stars and accreting compact objects through the history of Universe is encoded in intensity extragalactic background (EBL). Knowledge EBL important to understand nature star formation galaxy evolution, but direct measurements are lim- ited Galactic other foreground emissions. Here we report an absorption feature seen combined spectra a sample gamma-ray blazars out redshift z$\sim$1.6. This caused attenuation gamma rays at optical UV frequencies, allowed us measure flux...
ABSTRACT Most of the celestial γ rays detected by Large Area Telescope (LAT) on board Fermi Gamma-ray Space originate from interstellar medium when energetic cosmic interact with nucleons and photons. Conventional point-source extended-source studies rely modeling this diffuse emission for accurate characterization. Here, we describe development Galactic Interstellar Emission Model (GIEM), which is standard adopted LAT Collaboration publicly available. This model based a linear combination...
Weakly interacting massive particles (WIMPs) are a theoretical class of that excellent dark matter candidates. WIMP annihilation or decay may produce essentially monochromatic γ rays detectable by the Fermi Large Area Telescope (LAT) against astrophysical γ-ray emission Galaxy. We have searched for spectral lines in energy range 5–300 GeV using 3.7 years data, reprocessed with updated instrument calibrations and an improved dispersion model compared to previous Fermi-LAT Collaboration line...
Abstract The Large Area Telescope (LAT) aboard the Fermi spacecraft routinely observes high-energy emission from gamma-ray bursts (GRBs). Here we present second catalog of LAT-detected GRBs, covering first 10 yr operations, 2008 to 2018 August 4. A total 186 GRBs are found; these, 91 show in range 30–100 MeV (17 which seen only this band) and 169 detected above 100 MeV. Most these sources were discovered by other instruments ( /GBM, Swift /BAT, AGILE, INTEGRAL ) or reported Interplanetary...
Abstract We present a search for spatial extension in high-latitude ( ) sources recent Fermi point source catalogs. The result is the High-Latitude Extended Sources Catalog, which provides extensions (or upper limits thereof) and likelihood profiles suite of tested morphologies. find 24 extended sources, 19 were not previously characterized as extended. These include that are potentially associated with supernova remnants star-forming regions. also found γ -ray emission vicinity Cen A radio...
The energy released by an active galactic nucleus (AGN) has a strong impact on the surrounding interstellar medium (ISM). This feedback is considered to be regulating factor for growth of central massive black hole, and rate star formation in galaxy. We have located, using Very Long Baseline Interferometry (VLBI), fast outflow neutral hydrogen young, restarted radio loud AGN 4C12.50. located 100 pc from where jet interacts with ISM, as well around associated lobe. These observations show...
We have performed an analysis of the diffuse gamma-ray emission with Fermi Large Area Telescope in Milky Way Halo region searching for a signal from dark matter annihilation or decay. In absence robust signal, constraints are presented. consider both gamma rays produced directly annihilation/decay and by inverse Compton scattering e+e- annihilation/decay. Conservative limits derived requiring that does not exceed observed emission. A second set more stringent is based on modeling foreground...
We report on results from new high-sensitivity, high-resolution 86GHz (3.5 millimeter) observations of the jet base in nearby radio galaxy M87, obtained by Very Long Baseline Array conjunction with Green Bank Telescope. The resulting image has a dynamic range exceeding 1500 to 1, highest ever achieved for this at frequency, resolving and imaging detailed formation/collimation structure down ~10 Schwarzschild radii (Rs). clearly confirms some important features known lower frequencies, i.e.,...
Gamma rays reveal the Universe's history How many stars have formed in Universe, and when did they do so? These fundamental questions are difficult to answer because there systematic uncertainties converting light we observe into total mass of galaxies. The Fermi-LAT Collaboration addressed these by exploiting way that gamma from distant blazars propagate through intergalactic space, which depends on amount emitted all collaboration found star formation peaked about 3 billion years after Big...
Current theories predict relativistic hadronic particle populations in clusters of galaxies addition to the already observed leptons. In these scenarios interactions give rise neutral pions which decay into γ rays that are potentially observable with Large Area Telescope (LAT) on board Fermi space telescope. We present a joint likelihood analysis searching for spatially extended γ-ray emission at locations 50 galaxy four years Fermi-LAT data under assumption universal cosmic-ray (CR) model...
The Fermi Large Area Telescope (LAT) observed two bright X-class solar flares on 2012 March 7, and detected gamma-rays up to 4 GeV. We both during the impulsive temporally-extended emission phases, with above 100 MeV lasting for approximately 20 hours. Accurate localization of gamma-ray production site(s) coincide active region from which X-ray emissions associated these originated. Our analysis >100 shows a relatively rapid monotonic decrease in flux first hour phase, much slower, almost...
The contribution of unresolved sources to the diffuse gamma-ray background could induce anisotropies in this emission on small angular scales. We analyze power spectrum measured by Fermi LAT at Galactic latitudes |b| > 30 deg four energy bins spanning 1 50 GeV. At multipoles \ell \ge 155, corresponding scales \lesssim 2 deg, above photon noise level is detected >99.99% CL 1-2 GeV, 2-5 and 5-10 GeV bins, >99% 10-50 Within each bin takes approximately same value all suggesting that it...
We report Fermi-LAT observations of the radio-loud AGN SBS 0846+513 (z=0.5835), optically classified as a Narrow-Line Seyfert 1 galaxy, together with new and archival radio-to-X-ray data. The source was not active at gamma-ray energies during first two years Fermi operation. A significant increase in activity observed 2010 October-2011 August. In particular strong flare 2011 June reaching an isotropic luminosity (0.1-300 GeV) 1.0x10^48 erg/s, comparable to that brightest flat spectrum radio...
We present a study of the sub-parsec scale radio structure galaxy 3C 84/NGC 1275 based on Very Long Baseline Array data at 43 GHz. discover limb brightening in "restarted" jet that is associated with 2005 outburst. In 1990s, was ridge rather than brightening, despite observations being done similar angular resolutions. This indicates transverse has recently changed. change morphology reveals an interesting agreement γ-ray flux increase, i.e., 1990s least seven times lower current one. One...
ABSTRACT We present results from γ -ray observations of the Coma cluster incorporating six years Fermi -LAT data and newly released “Pass 8” event-level analysis. Our analysis region reveals low-significance residual structures within virial radius that are too faint for a detailed investigation with current data. Using likelihood approach is free assumptions on spectral shape we derive upper limits flux expected energetic particle interactions in cluster. also consider benchmark spatial...
We search for evidence of dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) measured with 50 months Fermi Large Area Telescope (LAT) observations. An improved theoretical description cosmological DM signal, based on two complementary techniques and assuming generic weakly interacting massive particle (WIMP) properties, renders more precise predictions compared to previous work. More specifically, we estimate cosmologically-induced intensity have an uncertainty a...
An incremental version of the fourth catalog active galactic nuclei (AGNs) detected by Fermi-Large Area Telescope is presented. This (4LAC-DR3) derives from third data release 4FGL based on 12 years E>50 MeV gamma-ray data, where spectral parameters, energy distributions (SEDs), yearly light curves, and associations have been updated for all sources. The new reported AGNs include 587 blazar candidates four radio galaxies. We describe properties sample outline changes affecting previously...