M. Villata
A5053651858- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Neutrino Physics Research
- Particle Accelerators and Free-Electron Lasers
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Gyrotron and Vacuum Electronics Research
- Calibration and Measurement Techniques
- Particle accelerators and beam dynamics
- Astronomy and Astrophysical Research
- Ionosphere and magnetosphere dynamics
- Particle physics theoretical and experimental studies
- Particle Detector Development and Performance
- Geophysics and Gravity Measurements
- Superconducting Materials and Applications
- Stellar, planetary, and galactic studies
- Magnetic confinement fusion research
- Computational Physics and Python Applications
- Cosmology and Gravitation Theories
- Adaptive optics and wavefront sensing
- Pulsars and Gravitational Waves Research
- Radiation Detection and Scintillator Technologies
Osservatorio Astrofisico di Torino
2015-2024
University of Siena
2023
Turku Centre for Computer Science
2023
University of Turku
2007-2023
Aalto University
2023
Foundation for Research and Technology Hellas
2023
Boston University
2023
Agenzia Spaziale Italiana
2023
National Institute for Astrophysics
2004-2018
Polytechnic University of Turin
2017
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...
Since the launch of Fermi satellite, BL Lacertae has been moderately active at gamma-rays and optical frequencies until May 2011, when source started a series strong flares. The exceptional sampling achieved by GLAST-AGILE Support Program (GASP) Whole Earth Blazar Telescope (WEBT) in collaboration with Steward Observatory allows us to perform detailed comparison daily gamma-ray observations Fermi. Discrete correlation analysis between emission reveals time lag 0 +- 1 d, which suggests...
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...
The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. maximum brightness detected was R = 12.0, which represents the most luminous state thus far observed (M_B ~ -31.4). In order to follow emission behaviour of source detail, a large multiwavelength campaign organized by Whole Earth Blazar Telescope (WEBT). Continuous optical, near-IR monitoring performed several bands. ToO pointings Chandra INTEGRAL satellites provided...
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...
Context. The quasar 3C 279 is among the most extreme blazars in terms of luminosity and variability flux at all wavebands. Its variations polarization are quite complex therefore require intensive monitoring observations multiple wavebands to characterise interpret observed changes.
Aims. Since the CGRO operation in 1991–2000, one of primary unresolved questions about blazar γ-ray emission has been its possible correlation with low-energy (in particular optical) emission. To help answer this problem, Whole Earth Blazar Telescope (WEBT) consortium organized GLAST-AGILE Support Program (GASP) to provide optical-to-radio monitoring data be compared detections by AGILE and GLAST satellites. This new WEBT project started early September 2007, just before a strong detection...
We present optical, X-ray, high energy ($\lessapprox 30$ GeV) and very ($\gtrapprox 100$ GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 June 23. A $\gamma$-ray signal was detected by AGILE with \sqrt{TS}=4.5 on 9--15, $F(E>100 \mathrm{MeV})= 42^{+14}_{-12}\times 10^{-8}$ photons cm$^{-2}$ s$^{-1}$. This flaring state is brighter than average flux observed EGRET a factor $\sim$3, but still consistent highest flux. In hard X-rays (20-60 keV)...
The gravitational behavior of antimatter is still unknown. While we may be confident that self-attractive, the interaction between matter and might either attractive or repulsive. We investigate this issue on theoretical grounds. Starting from CPT invariance physical laws, transform into in equations both electrodynamics gravitation. In former case, result well-known change sign electric charge. latter, find a mutual repulsion, i.e. antigravity appears as prediction general relativity when...
We report on 18 months of multiwavelength observations the blazar 3C 454.3 (Crazy Diamond) carried out in July 2007-January 2009. show results AGILE campaigns which took place May-June 2008, July-August and October 2008-January During May 2009 period, source average flux was highly variable, from an gamma-ray F(E>100MeV) > 200E-8 ph/cm2/s to F(E>100MeV)~80E-8 The spectrum between 100 MeV 1 GeV can be fit by a simple power law (Gamma_GRID ~ 2.0 2.2). Only 3-sigma upper limits derived 20-60...
Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all frequencies, and during last four years it exhibited more than one γ-ray flare per year, becoming most active in sky. We present for first time multi-wavelength AGILE, Swift, INTEGRAL, GASP-WEBT data collected order to explain extraordinary of which occurred 2010 November. On November 20 (MJD 55520), reached a peak flux (E >100 MeV) Fpγ = (6.8 ± 1.0) × 10−5 photons cm−2 s−1 on timescale about 12 hr, factor six...
Abstract In an effort to locate the sites of emission at different frequencies and physical processes causing variability in blazar jets, we have obtained high time-resolution observations BL Lacertae over a wide wavelength range: with Transiting Exoplanet Survey Satellite (TESS) 6000–10000 Å 2 minute cadence; Neil Gehrels Swift satellite optical, UV, X-ray bands; Nuclear Spectroscopic Telescope Array hard Fermi Large Area γ -ray energies; Whole Earth Blazar for measurement optical flux...
We present photometric sequences in the Johnson's BV and Cousins' R bands fields of 10 BL Lacertae objects (BL Lacs) monitored at Torino Astronomical Observatory. Data were taken during 14 nights from February 1995 to May 1997. The 56 calibrated stars are brighter than can be used as comparison order derive Lac magnitudes. Finding charts included for identification.
We present new BeppoSAX observations of the TeV-emitting blazar Mrk 501 performed in 1999 June and a homogeneous reanalysis all during period from 1997 April to June. Recently published TeV spectra by Cerenko Array at Themis, which are quasi-simultaneous with pointings, used constrain further physical parameters jet detailed models X-ray components. During 1997-1999 period, peak frequency synchrotron emission moved about 100 keV 0.5 The shift appears be correlated long-term luminosity...
Aims. The Whole Earth Blazar Telescope (WEBT) consortium has been monitoring the blazar 3C 454.3 from radio to optical bands since 2004 study its emission variability properties.
The blazar 3C 454.3 underwent an unprecedented optical outburst in spring 2005. This was first followed by a mm and then cm radio outburst, which peaked February 2006. We report on follow-up observations the WEBT to study multiwavelength emission post-outburst phase. XMM-Newton July December 2006 added information X-ray UV fluxes. source faint state. flux at higher frequencies showed fast decreasing trend, represents tail of big outburst. It quiescent state, common all frequencies. In...