A5057427631- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Astronomical Observations and Instrumentation
- SAS software applications and methods
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Neutrino Physics Research
- Particle Accelerators and Free-Electron Lasers
- Solar and Space Plasma Dynamics
- Pulsars and Gravitational Waves Research
- Calibration and Measurement Techniques
- Stellar, planetary, and galactic studies
- Adaptive optics and wavefront sensing
- Radiation Detection and Scintillator Technologies
- Astro and Planetary Science
- Particle physics theoretical and experimental studies
- Gyrotron and Vacuum Electronics Research
- Mechanical Circulatory Support Devices
- Cardiovascular Function and Risk Factors
- Particle accelerators and beam dynamics
- Galaxies: Formation, Evolution, Phenomena
- Infrared Target Detection Methodologies
University of Perugia
2015-2024
Brera Astronomical Observatory
2004-2023
National Institute for Astrophysics
2009-2023
Osservatorio Astrofisico di Catania
2021-2023
Istituto di Astrofisica Spaziale e Fisica cosmica di Palermo
2022-2023
Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano
2023
Astronomical Observatory of Rome
2009-2023
Osservatorio Astronomico di Padova
2010-2022
Istituto Nazionale di Fisica Nucleare, Sezione di Perugia
2010-2021
Istituto Nazionale di Fisica Nucleare
1998-2021
We report on the search for spectral irregularities induced by oscillations between photons and axionlike-particles (ALPs) in γ-ray spectrum of NGC 1275, central galaxy Perseus cluster. Using 6 years Fermi Large Area Telescope data, we find no evidence ALPs exclude couplings above 5×10^{-12} GeV^{-1} ALP masses 0.5≲m_{a}≲5 neV at 95% confidence. The limits are competitive with sensitivity planned laboratory experiments, and, together other bounds, strongly constrain possibility that can...
We present results from a deep spectral analysis of all the Swift observations Mrk 421 April 2006 to July 2006, when it reached its largest X-ray flux recorded until 2006. The peak was about 85 milli-Crab in 2.0-10.0 keV band, with energy (Ep) distribution (SED) laying often at energies larger than 10 keV. performed investigating trends parameters terms acceleration and energetic features phenomenologically linked SSC model parameters, predicting their effects gamma-ray particular shape...
Gamma-ray burst (GRB) emission is believed to originate in highly relativistic fireballs. Currently, only lower limits were securely set the initial fireball Lorentz factor Gamma_0. We aim provide a direct measure of The early-time afterglow light curve carries information about Gamma_0, which determines time peak. have obtained early observations near-infrared afterglows GRB 060418 and 060607A with REM robotic telescope. For both events, peak could be clearly singled out, allowing firm...
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...
Eight optical and four radio observatories have been intensively monitoring the BL Lac object 0716+714 in last years: 4854 data points collected UBVRI bands since 1994, while light curves extend back to 1978. Many of these are presented here for first time. The long-term trend shown by seems vary with a characteristic time scale about 3.3 years, longer period 5.5-6 years characterize variations. In general, colour indices only weakly correlated brightness. flux behaviour at different...
We present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during first two years Fermi Gamma-ray Space Telescope mission. While investigating previously reported gamma-ray/optical flare accompanied by a change in optical polarization, we found that emission appears delayed with respect to gamma-ray about 10 days. X-ray reveal pair `isolated' flares separated ~90 days, only weak counterparts. The spectral structure measured...
We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard gamma-ray bands. Our unique set has allowed us demonstrate that selection method strongly influences results, producing biases cannot be ignored. Almost all BL Lac objects have been detected by Fermi-LAT, whereas ~40% of flat-spectrum radio quasars (FSRQs) radio, X-ray selected are still below detection limit even after integrating 27 months...
We present the results of extensive multi-waveband monitoring blazar 3C~279 between 1996 and 2007 at X-ray energies (2-10 keV), optical R band, 14.5 GHz, as well imaging with Very Long Baseline Array (VLBA) 43 GHz. In all bands power spectral density corresponds to "red noise" that can be fit by a single law over sampled time scales. Variations in flux three wavebands are significantly correlated. The delay high low frequency changes substantially on scales years. A major multi-frequency...
We present a catalog of radio-loud candidate gamma-ray emitting blazars with WISE mid-infrared colors similar to the confirmed blazars. The is assembled from sources detected in all four filters, compatible three-dimensional locus blazars, and which can be spatially cross-matched radio either one three surveys: NVSS, FIRST and/or SUMSS. Our initial selection uses slightly modified version previously successful algorithms. then select only using measure radio-to-IR flux, q22 parameter,...
Despite the large number of discoveries made recently by Fermi, origins so called unidentified gamma-ray sources remain unknown. The these suggests that among them there could be a population significantly contributes to isotropic background and is therefore crucial understand their nature. first step toward complete comprehension source identify those can associated with blazars, most numerous class extragalactic in sky. Recently, we discovered blazars recognized separated from other using...
Blazars constitute the most enigmatic class of extragalactic gamma-ray sources, and their observational features have been ascribed to a relativistic jet closely aligned line sight. They are generally divided in two main classes: BL Lac objects (BL Lacs) Flat Spectrum Radio Quasars (FSRQs). In case Lacs double bumped spectral energy distribution (SED) is described by Synchrotron Self Compton (SSC) emission, while for FSRQs it interpreted as due External (EC) emission. Recently, we showed...
The gamma-ray emission in broad-line blazars is generally explained as inverse Compton (IC) radiation of relativistic electrons the jet scattering optical-UV photons from Broad Line Region (BLR), so-called BLR External scenario. We test this scenario on Fermi spectra 106 detected with highest significance or largest BLR, by looking for cut-off signatures at high energies compatible gamma-gamma interactions photons. do not find evidence expected absorption. For 2/3 sources, we can exclude any...
The ASTRI Mini-Array (MA) is an INAF project to build and operate a facility study astronomical sources emitting at very high-energy in the TeV spectral band. MA consists of group nine innovative Imaging Atmospheric Cherenkov telescopes. telescopes will be installed Teide Astronomical Observatory Instituto de Astrofisica Canarias (IAC) Tenerife (Canary Islands, Spain) on basis host agreement with INAF. Thanks its expected overall performance, better than those current telescopes' arrays for...
The BL Lacertae object AO 0235+16 is well known for its extreme optical and radio variability. New data have been collected in the last four years by a wide international collaboration, which confirm intense activity of this source: on long term, overall variations R band up to factor 18 fluxes were detected, while short-term variability few hours one day was observed band. also include results Whole Earth Blazar Telescope (WEBT) first-light campaign organized November 1997, involving dozen...
We present UBVRI light curves of BL Lacertae from May 2000 to January 2001, obtained by 24 telescopes in 11 countries. More than 15000 observations were performed that period, which was the extension Whole Earth Blazar Telescope (WEBT) campaign originally planned for July-August 2000. Rapid flux oscillations are all time, involving variations up a few tenths mag on hour time scales, and witnessing an intense intraday activity this source. Colour indexes have been derived coupling highest...
Of the blazars detected by EGRET in GeV γ-rays, 3C 279 is not only best observed but also one of monitored at lower frequencies. We have assembled 11 spectra, from GHz radio through time intervals observations. Although some data appeared previous publications, most are new, including taken during high states early 1999 and 2000. All spectra show substantial γ-ray contribution to total luminosity object; a state, dominates over that all other frequencies factor more than 10. There no clear...
BL Lacertae has been the target of four observing campaigns by Whole Earth Blazar Telescope (WEBT) collaboration. In this paper we present $UBVRI$ light curves obtained WEBT from 1994 to 2002, including last, extended Lac 2001 campaign. A total about 7500 optical observations performed 31 telescopes Japan Mexico have collected, be added $\sim 15600$ Campaign 2000. All these data allow one follow source emission behaviour with unprecedented detail. The analysis colour indices reveals that...
Curved broad-band spectral distributions of non-thermal sources like blazars are described well by a log-parabolic law where the second degree term measures curvature. Log-parabolic energy spectra can be obtained for relativistic electrons means statistical acceleration mechanism whose probability depends on energy. In this paper we compute radiated an electron population via synchrotron and Synchro-Self Compton processes to derive relations between parameters. These were accurate numerical...
The nearby Large Magellanic Cloud (LMC) provides a rare opportunity of spatially resolved view an external star-forming galaxy in gamma-rays. LMC was detected at 0.1-100GeV as extended source with CGRO/EGRET and using early observations the Fermi-LAT. emission found to correlate massive regions be particularly bright towards 30 Doradus. Studies origin transport cosmic rays (CRs) Milky Way are frequently hampered by line-of-sight confusion poor distance determination. offers complementary way...
Blazars, one of the most extreme class active galaxies, constitute so far largest known population $\gamma$-ray sources and their number is continuously growing in Fermi catalogs. However latest release catalog there still a large fraction that are classified as blazar candidate uncertain type (BCUs) for which optical spectroscopic observations necessary to confirm nature associations. In addition about 1/3 point listed Third Fermi-LAT Source Catalog (3FGL) unassociated lacking an assigned...
We present the results of a series Swift and quasi simultaneous ground-based infra-red observations blazar 3C 454.3 carried out in April-May 2005 when source was 10 to 30 times brighter than previously observed. found be very bright variable at all frequencies covered by our instrumentation. The broad-band Spectral Energy Distribution (SED) shows usual two-bump shape (in nu-nu f(nu) space) with Infra-red, optical UV data sampling declining part synchrotron emission that, even during this...
We present VRc Ic Johnson-Cousins magnitudes of field comparison stars for twelve BL Lacertae objects belonging to the largest sample blazars which is monitored at Perugia University Observatory. The sequences reported here can be used in long–term CCD photometric monitoring Lac aimed understand characteristics their variability. Finding charts all these are also included this paper.