S. Federici
A5090679714- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Particle Detector Development and Performance
- Pulsars and Gravitational Waves Research
- Corneal Surgery and Treatments
- Corneal surgery and disorders
- Computational Physics and Python Applications
- Radiation Therapy and Dosimetry
- Textile materials and evaluations
- Solar and Space Plasma Dynamics
- Meat and Animal Product Quality
- Photocathodes and Microchannel Plates
- Probiotics and Fermented Foods
- Glaucoma and retinal disorders
- Cosmology and Gravitation Theories
- Animal Diversity and Health Studies
- Dyeing and Modifying Textile Fibers
- Astronomical Observations and Instrumentation
- Particle Accelerators and Free-Electron Lasers
- Astronomy and Astrophysical Research
University of Potsdam
2011-2016
University of Chicago
2016
University of Amsterdam
2014
Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account weak energy losses, can accumulate, suggesting that may also sources very high (VHE; E > 100 GeV) gamma-ray emission. We report here VHE observations the Coma cluster with VERITAS array imaging Cerenkov telescopes, complementing Fermi Large Area Telescope at GeV energies. No significant emission from Cluster was detected. Integral flux...
We report on the detection of a very rapid TeV gamma-ray flare from BL Lacertae 2011 June 28 with Very Energetic Radiation Imaging Telescope Array System (VERITAS). The flaring activity was observed during 34.6-minute exposure, when integral flux above 200 GeV reached $(3.4\pm0.6) \times 10^{-6} \;\text{photons}\;\text{m}^{-2}\text{s}^{-1}$, roughly 125% Crab Nebula measured by VERITAS. light curve indicates that observations missed rising phase but covered significant portion decaying...
The high-frequency-peaked BL Lacertae object 1ES 0229+200 is a relatively distant (z = 0.1396), hard-spectrum (Gamma ~ 2.5), very-high-energy-emitting (E > 100 GeV) gamma-ray blazar. Very-high-energy measurements of this active galactic nucleus have been used to place constraints on the intensity extragalactic background light and intergalactic magnetic field. A multi-wavelength study centered around very-high-energy observations by VERITAS presented. This obtained, over period three years,...
TeV J2032+4130 was the first unidentified source discovered at very high energies (VHE; E $>$ 100 GeV), with no obvious counterpart in any other wavelength. It is also extended to be observed VHE gamma rays. Following its discovery, intensive observational campaigns have been carried out all wavelengths order understand nature of object, which met limited success. We report here on a deep observation J2032+4130, based 48.2 hours data taken from 2009 2012 by VERITAS (Very Energetic Radiation...
We present very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory. The bright extended ($\sim2^{\circ}$) unidentified Milagro source is located towards rich star formation region Cygnus-X. resolved into two sources. faint point-like VER J2016+371 overlaps CTB 87, a filled-center remnant (SNR) no evidence supernova shell at time. Its spectrum well fit in $0.65 - 10$ TeV range by power-law model photon index $2.3\pm0.4$. J2019+368 ($\sim1^{\circ}$) source, that...
HESS J0632+057 is the only gamma-ray binary known so far whose position in sky allows observations with ground-based observatories both northern and southern hemispheres. Here we report on long-term of conducted Very Energetic Radiation Imaging Telescope Array System High Energy Stereoscopic Cherenkov telescopes X-ray satellite Swift, spanning a time range from 2004 to 2012 covering most system's orbit. The very-high-energy (VHE) emission found be variable correlated that at energies. An...
We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope and UV Optical data between 2009 February 19 2013 June 8. This resides at a redshift $z\ge0.6035$, displaying significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production extragalactic background light. more than hours from three years, multiwavelength light curve spectral energy distributions. The source shows...
In 2013 March, a flaring episode from the Crab Nebula lasting ∼2 weeks was detected by Fermi-LAT (Large Area Telescope on board Fermi Gamma-ray Space Telescope). The Very Energetic Radiation Imaging Array System (VERITAS) provides simultaneous observations throughout this period. During flare, 20 fold increase in flux above average synchrotron >100 MeV seen Nebula. Simultaneous measurements with VERITAS are consistent non-variable long-term at TeV energies. Assuming linear correlation...
We report the discovery of an unidentified, extended source very-high-energy (VHE) gamma-ray emission, VER J2019+407, within radio shell supernova remnant SNR G78.2+2.1, using 21.4 hours data taken by VERITAS observatory in 2009. These confirm preliminary indications emission previously seen a two-year (2007-2009) blind survey Cygnus region VERITAS. which is detected at post-trials significance 7.5 standard deviations 2009 data, localized to northwestern rim enhanced and X-ray emission. It...
We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band by robotic telescopes Super-LOTIS and iTelescope, UV Swift UVOT, X-ray Telescope (XRT), high-energy gamma-ray with Fermi Large Area (LAT) very-high-energy (VHE) VERITAS above 315 GeV, all taken between 17 April 2012 1 June (MJD 56034 56079). The contemporaneous variability spectral energy distribution is explored in context a simple synchrotron self Compton (SSC) model. In SSC emission...
We report the detection of a new TeV gamma-ray source, VER J0521+211, based on observations made with VERITAS imaging atmospheric Cherenkov telescope array. These were motivated by discovery cluster >30GeV photons in first year Fermi-LAT observations. J0521+211 is relatively bright at energies, mean photon flux 1.93 +/- 0.13_stat 0.78_sys 10^-11 cm-2 s-1 above 0.2 during period The source strongly variable daily timescale across all wavebands, from optical to TeV, peak corresponding ~0.3...
We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 560\,GeV, is well described by a power law with spectral index $4.33 \pm 0.09$. integral flux above $200\,$GeV for this period was $(1.69 0.06) \times 10^{-11} \, \mathrm{ph} \mathrm{cm}^{-2} \mathrm{s}^{-1}$, corresponding to 6.9\% Crab Nebula flux. also combined $\gamma$-ray spectrum Fermi Large Area Telescope covering an energy...
We report on the VERITAS observations of high-frequency peaked BL Lac object 1ES 1959+650 in period 2007–2011. This source is detected at TeV energies by 16.4 standard deviation (σ) significance 7.6 hr observation a low flux state. A multiwavelength spectral energy distribution (SED) constructed from contemporaneous data VERITAS, Fermi-LAT, RXTE PCA, and Swift UVOT. XRT not included SED due to lack simultaneous with VERITAS. In contrast orphan γ-ray flare exhibited this 2002, X-ray found...
We present observations of the BL Lac object 1ES 0414+009 in >200 GeV gamma-ray band by VERITAS array Cherenkov telescopes. was observed between 2008 January and 2011 February, resulting 56.2 hr good quality pointed observations. These resulted a detection 822 events from source corresponding to statistical significance 6.4 standard deviations (6.4σ) above background. The flux, showing no evidence for variability, is measured as (5.2 ± 1.1stat 2.6sys) × 10−12 photons cm−2 s−1 200 GeV,...
We report on VERITAS observations of the BL Lac object B2 1215+30 between 2008 and 2012. During this period, source was detected at very high energies (VHEs; E > 100 GeV) by with a significance 8.9σ showed clear variability timescales larger than months. In 2011, found to be in relatively bright state power-law fit differential photon spectrum yields spectral index 3.6 ± 0.4stat 0.3syst an integral flux above 200 GeV (8.0 0.9stat 3.2syst) × 10−12 cm−2 s−1. No short term could during 2011....
We report on deep observations of the extended TeV gamma-ray source MGRO J1908+06 made with VERITAS very high energy (VHE) observatory. Previously, emission has been attributed to pulsar wind nebula (PWN) Fermi-LAT PSR J1907+0602. detect at a significance level 14 standard deviations (14 sigma) and measure photon index 2.20 +/- 0.10_stat 0.20_sys. The is extended, covering region near J1907+0602 also extending towards SNR G40.5--0.5. When fitted 2-dimensional Gaussian, intrinsic extension...
The Galactic center is an interesting region for high-energy (0.1-100 GeV) and very-high-energy (E > 100 gamma-ray observations. Potential sources of GeV/TeV emission have been suggested, e.g., the accretion matter onto supermassive black hole, cosmic rays from a nearby supernova remnant (e.g. SgrA East), particle acceleration in plerion, or annihilation dark particles. has detected by EGRET Fermi/LAT MeV/GeV energy band. At TeV energies, was with moderate significance CANGAROO Whipple 10...
RX J1713.7-3946 is the brightest shell-type Supernova remnant (SNR) of TeV gamma-ray sky. Earlier Fermi-LAT results on low-energy emission suggested that, despite large uncertainties in background determination, spectrum inconsistent with a hadronic origin. We update GeV-band spectra using improved estimates for diffuse galactic and more than doubled data volume. further investigate viability models J1713.7-3946. produced high-resolution map Galactic corrected HI self-absorption used it...
The very high energy (VHE; E $>$ 100 GeV) blazar Markarian 501 was observed between April 17 and May 5 (MJD 54938--54956), 2009, as part of an extensive multi-wavelength campaign from radio to VHE. Strong VHE $\gamma$-ray activity detected on 1st with Whipple VERITAS, when the flux (E 400 increased 10 times pre-flare baseline ($3.9{\times 10^{-11}}~{\rm ph~cm^{-2}~s^{-1}}$), reaching five Crab Nebula. This coincided a decrease in optical polarization rotation angle by 15$^{\circ}$. flare...
We report the discovery of TeV gamma-ray emission coincident with shell-type radio supernova remnant (SNR) CTA 1 using VERITAS observatory. The source, VER J0006+729, was detected as a 6.5 standard deviation excess over background and shows an extended morphology, approximated by two-dimensional Gaussian semimajor (semiminor) axis 030 (024) centroid 5' from Fermi pulsar PSR J0007+7303 its X-ray wind nebula (PWN). photon spectrum is well described power-law dN/dE = N0(E/3 TeV)−Γ, differential...
Prompt emission from the very fluent and nearby (z = 0.34) gamma-ray burst GRB 130427A was detected by several orbiting telescopes ground-based, wide-field-of-view optical transient monitors. Apart intensity proximity of this GRB, it is exceptional due to extremely long-lived high-energy (100 MeV 100 GeV) emission, which Large Area Telescope on Fermi Gamma-Ray Space for ∼70 ks after initial burst. The persistent, hard-spectrum, suggests that highest-energy gamma rays may have been produced...
The indirect detection of dark matter requires that annihilation products be discriminated from conventional astrophysical backgrounds. Here, we re-analyze GeV-band gamma-ray observations the prominent Milky Way dwarf satellite galaxy Segue 1, for which expected background is minimal. We explicitly account angular extent conservatively signal and keep uncertainty in dark-matter profile external to likelihood analysis data.
We report results from TeV gamma-ray observations of the microquasar Cygnus X-3. The were made with Very Energetic Radiation Imaging Telescope Array System (VERITAS) over a time period 2007 June 11 to 2011 November 28. VERITAS is most sensitive gamma rays at energies between 85 GeV and 30 TeV. effective exposure amounts total about 44 hr, covering six distinct radio/X-ray states object. No significant emission was detected in any states, nor all combined. lack positive signal, especially...