A5006916633- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Particle physics theoretical and experimental studies
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Particle Detector Development and Performance
- Galaxies: Formation, Evolution, Phenomena
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
- Cosmology and Gravitation Theories
- Astro and Planetary Science
- Nuclear Physics and Applications
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Geophysics and Gravity Measurements
- Radiation Therapy and Dosimetry
- Ionosphere and magnetosphere dynamics
- Seismology and Earthquake Studies
- Radioactivity and Radon Measurements
- Calibration and Measurement Techniques
Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
2015-2018
University of Padua
2011-2015
University of Pisa
2015
Istituto Nazionale di Fisica Nucleare, Sezione di Padova
2011-2013
Fermi National Accelerator Laboratory
2012
The Ohio State University
2012
California Institute of Technology
2012
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...
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...
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...
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...
Dark matter particle annihilation or decay can produce monochromatic gamma-ray lines and contribute to the diffuse background. Flux upper limits are presented for spectral from 7 200 GeV background 4.8 264 obtained two years of Fermi Large Area Telescope data integrated over most sky. We give cross-section lifetime lower dark models that spectrum, including proposed as explanations PAMELA cosmic-ray data.
On 2015 June 16, Fermi-LAT observed a giant outburst from the flat spectrum radio quasar 3C 279 with peak $>100$ MeV flux of $\sim3.6\times10^{-5}\;{\rm photons}\;{\rm cm}^{-2}\;{\rm s}^{-1}$ averaged over orbital period intervals. It is historically highest $\gamma$-ray source including past EGRET observations, isotropic luminosity reaching $\sim10^{49}\;{\rm erg}\;{\rm s}^{-1}$. During outburst, Fermi spacecraft, which has an 95.4 min, was operated in special pointing mode to optimize...
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 a measurement of the cosmic-ray electron+positron spectrum between 7 GeV and 2 TeV performed with almost seven years data collected Fermi Large Area Telescope. find that is well fit by broken power law break energy at about 50 GeV. Above GeV, described single spectral index $3.07 \pm 0.02 \; (\text{stat+syst}) 0.04 (\text{energy measurement})$. An exponential cutoff lower than 1.8 excluded 95\% CL.
GRB110721A was observed by the Fermi Gamma-ray Space Telescope using its two instruments Large Area (LAT) and Burst Monitor (GBM). The burst consisted of one major emission episode which lasted for ~24.5 seconds (in GBM) had a peak flux 5.7\pm0.2 x 10^{-5} erg/s/cm^2. time-resolved spectrum is best modeled with combination Band function blackbody spectrum. energy component initially 15\pm2 MeV, highest value ever detected in GRB. This measurement made possible combining GBM/BGO data LAT Low...
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...
Numerical simulations based on the Lambda-CDM model of cosmology predict a large number as yet unobserved Galactic dark matter satellites. We report results Large Area Telescope (LAT) search for these satellites via gamma-ray emission expected from annihilation weakly interacting massive particle (WIMP) matter. Some are to have hard spectra, finite angular extents, and lack counterparts at other wavelengths. sought identify LAT sources with characteristics, focusing spectra consistent WIMP...
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...
Long-term monitoring of PSR J2021+4026 in the heart Cygnus region with Fermi Large Area Telescope unveiled a sudden decrease flux above 100 MeV over timescale shorter than week. The "jump" was near MJD 55850 (2011 October 16), decreasing from (8.33 ± 0.08) × 10−10 erg cm−2 s−1 to (6.86 0.13) s−1. Simultaneously, frequency spindown rate increased (7.8 0.1) 10−13 Hz (8.1 Significant (>5σ) changes pulse profile and marginal (<3σ) emission spectrum occurred at same time. There is also evidence...
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...
ABSTRACT We report the Fermi Large Area Telescope (LAT) detections of high-energy (>100 MeV) γ -ray emission from two recent optically bright classical novae, V1369 Centauri 2013 and V5668 Sagittarii 2015. At early times, target-of-opportunity observations prompted by their optical discoveries provided enhanced LAT exposure that enabled onsets beginning ∼2 days after first peaks. Significant was found extending to 39–55 initial detections, with systematically fainter longer-duration...
ABSTRACT We report the Fermi Large Area Telescope detection of extended γ -ray emission from lobes radio galaxy Fornax A using 6.1 years Pass 8 data. After Centaurus A, this is now second example an source attributed to a galaxy. Both flat disk morphology and following were preferred over point-source description, core contribution was constrained be <?CDATA $\lt 14$?> % total flux. alignment elongation with demonstrated by rotating template. found no significant evidence for variability on...
Galaxy clusters are one of the prime sites to search for dark matter (DM) annihilation signals. Depending on substructure DM halo a galaxy cluster and cross sections channels, these signals might be detectable by latest generation $\gamma$-ray telescopes. Here we use three years Fermi Large Area Telescope (LAT) data, which most suitable searching very extended emission in vicinity nearby Virgo cluster. Our analysis reveals statistically significant can well characterized uniformly emitting...
The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space routinely detects highly dust-absorbed, reddened, and MeV-peaked flat spectrum radio quasar PKS 1830-211 (z=2.507). Its apparent isotropic gamma-ray luminosity (E>100 MeV) averaged over $\sim$ 3 years of observations peaking 2010 October 14/15 at 2.9 X 10^{50} erg s^{-1}, makes it among brightest high-redshift blazars. No published model with a single lens can account for all observed characteristics this complex system. Based...
The Large Area Telescope on board the Fermi Gamma-ray Space has collected largest ever sample of high-energy cosmic-ray electron and positron events since beginning its operation. Potential anisotropies in arrival directions electrons or positrons could be a signature presence nearby sources. We use almost seven years data with energies above 42 GeV processed Pass 8 reconstruction. present can probe dipole down to level 10^{-3}. take into account systematic effects that mimic true at this...
We report on a systematic investigation of the gamma-ray properties 120 hard X-ray-selected Seyfert galaxies classified as `radio-quiet' objects, utilizing three-year accumulation Fermi-LAT data. Our sample is selected using Swift-BAT 58-month catalog, restricting analysis to bright sources with average X-ray fluxes F(14-195 keV) > 2.5x10-11 erg cm-2 s-1 at high Galactic latitudes (|b|>10 deg). In order remove `radio-loud' objects from sample, we use `hard radio loudness parameter', Rrx,...
We examine 288 GRBs detected by the Fermi Gamma-ray Space Telescope's Burst Monitor (GBM) that fell within field-of-view of Fermi's Large Area Telescope (LAT) during first 2.5 years observations, which showed no evidence for emission above 100 MeV. report photon flux upper limits in 0.1-10 GeV range prompt phase as well fixed 30 s and integrations starting from trigger time each burst. compare these with fluxes would be expected extrapolations spectral fits presented GBM catalog infer...
Pulsars are rapidly spinning, highly magnetized neutron stars, created in the gravitational collapse of massive stars. We report detection pulsed giga-electron volt gamma rays from young pulsar PSR J0540-6919 Large Magellanic Cloud, a satellite galaxy Milky Way. This is first gamma-ray detected another galaxy. It has most luminous emission yet observed, exceeding Crab pulsar's by factor 20. presents an extreme test case for understanding structure and evolution star magnetospheres.
The discovery of rapidly variable Very High Energy (VHE; E > 100 GeV) gamma-ray emission from 4C +21.35 (PKS 1222+216) by MAGIC on 2010 June 17, triggered the high activity detected Fermi Large Area Telescope (LAT) in energy (HE; MeV) gamma-rays, poses intriguing questions location emitting region this flat spectrum radio quasar. We present multifrequency data collected centimeter to VHE during investigate properties source and discuss a possible model. first hint detection at was observed...
Supernovae (SNe) exploding in a dense circumstellar medium (CSM) are hypothesized to accelerate cosmic rays collisionless shocks and emit GeV γ-rays TeV neutrinos on timescale of several months. We perform the first systematic search for γ-ray emission Fermi Large Area Telescope data energy range from ensemble 147 SNe Type IIn CSM. excess at each location one-year time window. In order enhance possible weak signal, we simultaneously study closest optically brightest sources our sample...