A5060557881- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Particle Accelerators and Free-Electron Lasers
- Solar and Space Plasma Dynamics
- Dark Matter and Cosmic Phenomena
- Neutrino Physics Research
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Particle accelerators and beam dynamics
- Particle physics theoretical and experimental studies
- Particle Detector Development and Performance
- Cosmology and Gravitation Theories
- Ionosphere and magnetosphere dynamics
- Nuclear Physics and Applications
- Astrophysics and Star Formation Studies
- Gyrotron and Vacuum Electronics Research
- Magnetic confinement fusion research
- Computational Physics and Python Applications
- Geophysics and Gravity Measurements
Scuola Internazionale Superiore di Studi Avanzati
2015-2024
Brera Astronomical Observatory
2015-2024
Istituto Nazionale di Fisica Nucleare, Sezione di Trieste
2014-2024
National Institute for Astrophysics
2009-2024
Institute for Fundamental Physics of the Universe
2020-2023
Istituto Nazionale di Fisica Nucleare
2018-2022
Trieste Astronomical Observatory
2017
University of Trieste
2007-2014
Universität Hamburg
2009
Max Planck Institute for Nuclear Physics
2009
We collect data at well-sampled frequencies from the radio to γ-ray range for following three complete samples of blazars: Slew survey, 1-Jy BL Lacs and 2-Jy sample flat-spectrum radio-loud quasars (FSRQs). The fraction objects detected in γ-rays (E ≳ 100 MeV) is ∼ 17, 26 40 per cent respectively. Except survey sample, sources do not differ either other each or all sources, terms distributions redshift, X-ray luminosities broad-band spectral indices (radio optical X-ray). compute average...
view Abstract Citations (912) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Jet Model for the Gamma-Ray--emitting Blazar 3C 279 Maraschi, L. ; Ghisellini, G. Celotti, A. The physical conditions in γ-ray-emitting blazar are discussed. requirement of transparency γ-rays, together with observation rapid variability, imply that high-energy radiation is anisotropic. It proposed γ-rays produced a relativistic jet via synchrotron self-Compton...
The phenomenology of gamma-ray bright blazars can be accounted for by a sequence in the source power and intensity diffuse radiation field surrounding relativistic jet. Correspondingly, equilibrium particle distribution peaks at different energies. This leads to trend observed properties: an increase corresponds to: 1) decrease frequencies synchrotron inverse Compton peaks; 2) ratio powers high low energy spectral components. Objects along this would observationally classified respectively...
Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Burst Monitor and Large Area Telescope onboard Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades gammaray energy. In September 2008, observed exceptionally luminous GRB 080916C, with largest apparent release yet measured. high-energy gamma rays to start later persist longer than lower photons. A simple spectral form fits entire...
We studied all blazars of known redshift detected by the Fermi satellite during its first 3-month survey. For majority them, pointed Swift observations ensure a good multiwavelength coverage, enabling us to reliably construct their spectral energy distributions (SEDs). model SEDs using one-zone leptonic and study derived interesting physical parameters as function observed γ-ray luminosity. confirm previous findings concerning relation with source luminosity which are at origin blazar...
view Abstract Citations (540) References (120) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Relativistic Bulk Motion in Active Galactic Nuclei Ghisellini, G. ; Padovani, P. Celotti, A. Maraschi, L. We discuss the evidence for relativistic bulk motion of emitting plasma nuclei ~100 radio sources, which include BL Lacertae objects, quasars, and galaxies, with published VBLI measurements core angular dimension flux. Comparing predicted observed high-frequency...
We present the first catalog of active galactic nuclei (AGNs) detected by Large Area Telescope (LAT), corresponding to 11 months data collected in scientific operation mode. The First LAT AGN Catalog (1LAC) includes 671 γ-ray sources located at high Galactic latitudes (|b|>10°) that are with a test statistic greater than 25 and associated statistically AGNs. Some multiple AGNs, consequently, 709 comprising 300 BL Lacertae objects, 296 flat-spectrum radio quasars, 41 AGNs other types, 72...
We estimate the power of relativistic, extragalactic jets by modelling spectral energy distribution a large number blazars. adopt simple one-zone, homogeneous, leptonic synchrotron and inverse Compton model, taking into account seed photons originating both locally in jet externally. The blazars under study have an often dominant high component, which, if interpreted as due to radiation, limits value magnetic field within emission region. As consequence, corresponding Poynting flux cannot be...
The central engine causing the production of jets in radio sources may work intermittently, accelerating shells plasma with different mass, energy and velocity. Faster but later can then catch up slower earlier ones. In resulting collisions shocks develop, converting some ordered bulk kinetic into magnetic field random electrons which radiate. We propose that this internal shock scenario, is scenario generally thought to explain observed gamma-ray burst radiation, also for general, blazars...
X-ray emission from large-scale extragalactic jets is likely to be as a result of inverse Compton scattering relativistic particles off seed photons both the cosmic microwave background field and blazar nucleus. The first process dominates observed high-energy if plasma moving at highly speeds jet aligned with line sight, i.e. in powerful flat radio spectrum quasars. second relevant when mildly bulk speeds, can dominate misaligned sources, galaxies. We show that this scenario satisfactorily...
According to the collapsar model, γ-ray bursts are thought be produced in shocks that occur after relativistic jet has broken free from stellar envelope. If mass density of collimated outflow is less than envelope, will then surrounded by a cocoon plasma. This material would itself able escape along direction least resistance, which likely rotation axis progenitor, and accelerate approximately same way as an impulsive fireball. We discuss how properties envelope have decisive effect on...
We study the emission observed at energies greater than 100 MeV of 11 Gamma Ray Bursts (GRBs) detected by Fermi/Large Area Telescope (LAT) until October 2009. The GeV has three main properties: (i) its duration is often longer softer Burst Monitor (GBM) onboard Fermi [this confirms earlier results from Energetic Gamma-Ray Experiment (EGRET)]; (ii) spectrum consistent with F(v) propto v^(-1) and does not show strong spectral evolution; (iii) for brightest bursts, flux LAT decays as a power...
We present evidence in favour of a link between the luminosity radiatively dissipated central engine radio-loud Active Galactic Nuclei and kinetic power their jets. This piece is based on relation we find broad emission lines pc-scale radio jets, for sample quasars which suitable data are available literature. that ionizing one same order magnitude, suggesting processes responsible them somehow related. A strong magnetic field equipartition with radiation could be regulating both processes....
The blazar 3C 279, one of the brightest identified extragalactic objects in γ-ray sky, underwent a large (factor ~10 amplitude) flare γ-rays toward end 3 week pointing by Compton Gamma Ray Observatory (CGRO), 1996 January-February. peak represents highest intensity ever recorded for this object. During high state, extremely rapid variability was seen, including an increase factor 2.6 ~8 hr, which strengthens case relativistic beaming. Coordinated multifrequency observations were carried out...
Recent observations have allowed the geometry and kinematics of M87 jet to be tightly constrained. We combine these constraints with historical Very Long Baseline Interferometry (VLBI) results theory synchrotron self-absorbed radio cores in order investigate physical properties jet. Our strongly suggest dominated by an electron-positron (pair) plasma. Although our conservative cannot conclusively dismiss electron-proton plasma, viability this solution is extremely vulnerable further...
We use the emission line measurements of 3CR radio sources with redshift < 0.3, to explore their spectroscopic properties. The show a bimodal distribution Excitation Index, new indicator that measures relative intensity low and high excitation lines. This unveils presence two main sub-populations radio-loud AGN, High Low Galaxies (HEG LEG, respectively). All broad-line objects are HEG from point view narrow ratios all FRII radio-galaxies log L(178) [erg/s] > 32.8. Conversely LEG cover whole...
We performed an observational program with the X-ray satellite BeppoSAX to study objects extreme synchrotron peak frequencies (nu_peak > 1 keV). Of seven sources observed, four showed in range 1-5 keV, while one (1ES 1426+428) displayed a flat power law spectrum (alpha= 0.92), locating its at or above 100 keV. This is third source of this type ever found, after Mkn 501 and 1ES 2344+514. Our data confirm large nu_peak variability class sources, compared lower peaked objects. The high...
We report the discovery of high-energy (E>100 MeV) gamma-ray emission from NGC 1275, a giant elliptical galaxy lying at center Perseus cluster galaxies, based on observations made with Large Area Telescope (LAT) Fermi Gamma ray Space Telescope. The positional source is only ~3' away 1275 nucleus, well within 95% LAT error circle ~5'.The spatial distribution photons consistent point source. average flux and power-law photon index measured 2008 August 4 to December 5 are F_gamma =...
Analysis is presented for 15 months of data taken with the Large Area Telescope (LAT) on Fermi Gamma-ray Space 11 non-blazar active galactic nuclei (AGNs), including seven FRI radio galaxies and four FRII sources consisting two steep spectrum quasars. The broad line galaxy 3C 120 reported here as a γ-ray source first time. analysis based directional associations LAT in 3CR, 3CRR, MS4 (collectively referred to 3C-MS) catalogs. Seven eleven associated 3C-MS have spectral indices larger than...
We present the results of spectral analysis public data 438 gamma ray bursts (GRBs) detected by Fermi Gamma Burst Monitor (GBM) up to March 2010. For 432 we could fit time-integrated spectrum. In 318 cases reliably constrain peak energy their νFν spectrum analyzing between 8 keV and 35 MeV. Eighty percent these spectra are fitted a power-law with an exponential cutoff, remaining Band function. Among GRBs, 274 belong long GRB class 44 short. Long GRBs have typical ~ 160 low-energy index α −...
We compare the spectral properties of 79 short and long Gamma-Ray Bursts (GRBs) detected by BATSE selected with same limiting peak flux. Short GRBs have a low-energy component harder energy slightly higher than GRBs, but no difference is found when comparing GRB spectra those first 1-2 s emission GRBs. These results confirm earlier findings for brighter The bolometric flux correlates their in similar way to bursts. populate different regions fluence-peak plane, bursts being less energetic...
We estimate the bulk Lorentz factor Gamma_0 of 31 GRBs using measured peak time their afterglow light curves. consider two possible scenarios for Gamma_0: case a homogeneous circumburst medium or wind density profile. The values are broadly distributed between few tens and several hundreds with average ~138 ~66 profile, respectively. find that isotropic energy luminosity correlate in similar way Gamma_0, i.e. Eiso Gamma_0^2 Liso Gamma_0^2, while Epeak Gamma_0. These correlations less...