G. Madejski
A5002514037- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Particle Accelerators and Free-Electron Lasers
- Radio Astronomy Observations and Technology
- Particle Detector Development and Performance
- Astronomical Observations and Instrumentation
- Dark Matter and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Neutrino Physics Research
- Solar and Space Plasma Dynamics
- Pulsars and Gravitational Waves Research
- Nuclear Physics and Applications
- Particle physics theoretical and experimental studies
- Particle accelerators and beam dynamics
- Adaptive optics and wavefront sensing
- Geophysics and Gravity Measurements
- Astrophysics and Star Formation Studies
- Gyrotron and Vacuum Electronics Research
- Computational Physics and Python Applications
- Cosmology and Gravitation Theories
- semigroups and automata theory
- DNA and Biological Computing
Kavli Institute for Particle Astrophysics and Cosmology
2014-2024
Stanford University
2013-2024
SLAC National Accelerator Laboratory
2015-2024
University of Gdańsk
2014-2024
Menlo School
2003-2023
California Institute of Technology
2018
Stanford Synchrotron Radiation Lightsource
2001-2007
Istituto Nazionale di Fisica Nucleare, Sezione di Perugia
2007
University of Perugia
2007
United States Naval Research Laboratory
2007
We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on first eight years science data from Gamma-ray Space mission in energy range 50 MeV to 1 TeV, it is deepest yet this range. Relative 3FGL catalog, 4FGL has twice as much exposure well a number analysis improvements, including an updated model for Galactic diffuse emission, and two sets light curves (1-year 2-month intervals). The includes 5064 sources above 4 sigma significance, which we provide...
Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) the sources of galactic cosmic rays, unequivocal evidence for acceleration protons in these objects is still lacking. When encounter interstellar material, they produce neutral pions, which turn decay into gamma rays. This offers a compelling way detect sites protons. The identification pion-decay has been difficult because high-energy electrons also via...
We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because instrument does not have an onboard magnet, we distinguish two species by exploiting Earth's shadow, which is offset in opposite directions for charges due to magnetic field. estimate subtract proton background using different methods that produce consistent results. report electron-only spectrum, positron-only fraction between 20 GeV 200 GeV. confirm rises energy 20-100 range. The...
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...
We present a catalog of sources detected above 50 GeV by the {\it Fermi}-Large Area Telescope (LAT) in 80 months data. The newly delivered Pass 8 event-level analysis allows detection and characterization GeV--2 TeV energy range. In this band, Fermi}-LAT has 360 sources, which constitute second hard (2FHL). improved angular resolution enables precise localization point ($\sim$1.7$'$ radius at 68 % C.~L.) spatially extended sources. find that 86 can be associated with counterparts other...
We present observations of the young supernova remnant (SNR) RX J1713.7−3946 with Fermi Large Area Telescope (LAT). clearly detect a source positionally coincident SNR. The is extended best-fit extension 055 ± 004 matching size non-thermal X-ray and TeV gamma-ray emission from remnant. positional coincidence allow us to identify LAT SNR J1713.7−3946. spectrum can be described by very hard power law photon index Γ = 1.5 0.1 that coincides in normalization steeper H.E.S.S.-detected at higher...
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...
Abstract Most of the light from blazars, active galactic nuclei with jets magnetized plasma that point nearly along line sight, is produced by high-energy particles, up to around 1 TeV. Although are known be ultimately powered a supermassive black hole, how particles accelerated such high energies has been an unanswered question. The process must related magnetic field, which can probed observations polarization jets. Measurements radio optical polarization—the only range available until...
We report observation of the supernova remnant IC443 (G189.1+3.0) with Fermi Gamma-ray Space Telescope Large Area (LAT) in energy band between 200MeV and 50GeV. is a shell-type mixed morphology located off outer Galactic plane where high-energy emission has been detected X-ray, GeV TeV gamma-ray bands. Past observations suggest interacting surrounding interstellar matter. Proximity dense shocked molecular clouds GeV-TeV regions by EGRET, MAGIC VERITAS suggests an interpretation that...
We report on the gamma-ray activity of blazar Mrk 501 during first 480 days Fermi operation. find that average LAT spectrum can be well described by a single power-law function with photon index 1.78 +/- 0.03. While we observe relatively mild flux variations Fermi-LAT (within less than factor 2), detect remarkable spectral variability where hardest observed within energy range is 1.52 0.14, and softest one 2.51 0.20. These unexpected changes do not correlate measured above 0.3GeV. In this...
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...
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...
The diffuse Galactic gamma-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on Compton Observatory indicated excess > 1 GeV relative to models consistent directly measured CR spectra (the so-called ``EGRET excess''). was observed in all directions sky, a variety of explanations have been proposed, including beyond-the-Standard-Model scenarios like annihilating or...
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by Institute Space and Astronautical Science (ISAS). will investigate physics high-energy universe performing high-resolution, high-throughput spectroscopy with moderate angular resolution. covers very wide energy range from 0.3 keV to 600 keV. allows combination band (5-80 keV) provided multilayer coating, focusing hard mirrors imaging detectors, high energy-resolution soft (0.3-12...
This article reviews the recent observational results regarding γ-ray emission from active galaxies. The most numerous discrete extragalactic sources are AGNs dominated by relativistic jets pointing in our direction (commonly known as blazars), and they main subject of review. They detected all observable energy bands highly variable. advent sensitive observations, afforded launch continuing operation Fermi Gamma-ray Space Telescope AGILE Imaging Detector, well deployment current-generation...
We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on first eight years science data from Gamma-ray Space mission in energy range 50 MeV to 1 TeV, it is deepest yet this range. Relative 3FGL catalog, 4FGL has twice as much exposure well a number analysis improvements, including an updated model for Galactic diffuse emission, and two sets light curves (1-year 2-month intervals). The includes 5064 sources above 4 sigma significance, which we provide...
We present X-ray spectral analyses for three Seyfert 2 active galactic nuclei, NGC 424, 1320, and IC 2560, observed by NuSTAR in the 3-79 keV band. The high quality hard spectra allow detailed modeling of Compton reflection component first time these sources. Using quasi-simultaneous Swift/XRT data, as well archival XMM-Newton we find that all nuclei are obscured Compton-thick material with column densities excess ~5 x $10^{24}$ cm$^{-2}$, their above 3 dominated intrinsic continuum on...
Abstract Particle acceleration mechanisms in supermassive black hole jets, such as shock acceleration, magnetic reconnection, and turbulence, are expected to have observable signatures the multiwavelength polarization properties of blazars. The recent launch Imaging X-Ray Polarimetry Explorer (IXPE) enables us, for first time, use X-ray band (2–8 keV) probe jet synchrotron emission high-synchrotron-peaked BL Lac objects (HSPs). We report discovery linear (degree Π x = 15% ± 2% electric...
We report on the first observation of a radio-quiet Active Galactic Nucleus (AGN) using polarized X-rays: Seyfert 1.9 galaxy MCG-05-23-16. This source was pointed with Imaging X-ray Polarimetry Explorer (IXPE) starting May 14, 2022 for net observing time 486 ks, simultaneously XMM-Newton (58 ks) and NuSTAR (83 ks). A polarization degree smaller than $\Pi<4.7\%$ (at 99% c.l.) is derived in 2-8 keV energy range, where emission dominated by primary component ascribed to hot corona. The...
ABSTRACT We present an X-ray spectro-polarimetric analysis of the bright Seyfert galaxy IC 4329A. The Imaging Polarimetry Explorer (IXPE) observed source for ∼500 ks, supported by XMM–Newton (∼60 ks) and NuSTAR (∼80 exposures. detect polarization in 2–8 keV band with 2.97σ confidence. report a degree 3.3 ± 1.1 per cent angle 78° 10° (errors are 1σ confidence). is consistent being aligned radio jet, albeit partially due to large uncertainties on position angle. jointly fit spectra from three...
Abstract We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/ γ -ray outburst, 287 ks observation (2022 November 27–30) was taken using Imaging Polarimetry Explorer (IXPE), together with contemporaneous multiwavelength observations from Neil Gehrels Swift observatory and XMM-Newton soft X-rays (0.3–10 keV), NuSTAR hard (3–70 optical Calar Alto Perkins Telescope observatories. Our data suggest that IXPE energy band is at crossover...
ABSTRACT We report on the second observation of radio-quiet active galactic nucleus MCG-05-23-16 performed with Imaging X-ray Polarimetry Explorer (IXPE). The started 2022 November 6 for a net observing time 640 ks, and was partly simultaneous NuSTAR (86 ks). After combining these data those obtained in first IXPE pointing May (simultaneous XMM–Newton NuSTAR) we find 2–8 keV polarization degree Π = 1.6 ± 0.7 (at 68 per cent confidence level), which corresponds to an upper limit 3.2 99...