Justin D. Finke
A5037339672- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Particle Detector Development and Performance
- Particle Accelerators and Free-Electron Lasers
- Astronomical Observations and Instrumentation
- Gyrotron and Vacuum Electronics Research
- Stellar, planetary, and galactic studies
- Pulsars and Gravitational Waves Research
- Computational Physics and Python Applications
- Astro and Planetary Science
- Particle physics theoretical and experimental studies
- Cosmology and Gravitation Theories
- Noncommutative and Quantum Gravity Theories
- Magnetic confinement fusion research
- Laser-Plasma Interactions and Diagnostics
- Geomagnetism and Paleomagnetism Studies
- Heat Transfer Mechanisms
- Ionosphere and magnetosphere dynamics
United States Naval Research Laboratory
2015-2024
University of Turku
2023
Universidad Complutense de Madrid
2023
Turku Centre for Computer Science
2023
Deutsches Elektronen-Synchrotron DESY
2023
Université Paris Cité
2023
Laboratoire AstroParticule et Cosmologie
2023
Centre National de la Recherche Scientifique
2023
Institut National de Physique Nucléaire et de Physique des Particules
2023
Laboratoire de Physique Nucléaire et de Hautes Énergies
2023
We present the third Fermi Large Area Telescope (LAT) source catalog (3FGL) of sources in 100 MeV–300 GeV range. Based on first 4 yr science data from Gamma-ray Space mission, it is deepest yet this energy Relative to Second LAT catalog, 3FGL incorporates twice as much data, well a number analysis improvements, including improved calibrations at event reconstruction level, an updated model for Galactic diffuse γ-ray emission, refined procedure detection, and methods associating with...
The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It based on (3FGL) sources between 100 MeV and 300 GeV with a Test Statistic (TS) greater than 25, 2008 August 4 2012 July 31. 3LAC includes 1591 AGNs located at high Galactic latitudes (|b|>10{\deg}), 71% increase over second 2 years data. There are 28 duplicate associations, thus 1563 2192 high-latitude gamma-ray 3FGL AGNs. Most them (98%) blazars. About half newly blazars unknown type, i.e.,...
The extragalactic background light (EBL) from the far infrared through visible and extending into ultraviolet is thought to be dominated by starlight, either direct emission or absorption reradiation dust. This most important energy range for absorbing $\g$-rays distant sources such as blazars gamma-ray bursts producing electron positron pairs. In previous work we presented EBL models in optical consistently taking account star formation rate (SFR), initial mass function (IMF) dust...
We report on the gamma-ray activity of high-synchrotron-peaked BL Lacertae object Mrk 421 during first 1.5 years Fermi operation, from 2008 August 5 to 2010 March 12. find that Large Area Telescope (LAT) spectrum above 0.3 GeV can be well-described by a power-law function with photon index Gamma=1.78 +/- 0.02 and average flux F(>0.3 GeV)=(7.23 0.16) x 10^{-8} ph cm^{-2} s^{-1}. Over this time period, Fermi-LAT was evaluated 7-day-long intervals, showing significant variations in (up factor...
The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area (4LAC) between 2008 August 4 and 2016 2 contains 2863 objects located at high Galactic latitudes (|b|>10{\deg}). It includes 85% more sources than previous 3LAC based on years data. AGNs represent least 79% high-latitude in Fermi-Large Source Catalog (4FGL), which covers energy range from 50 MeV to 1 TeV. In addition, 344 gamma-ray are found low latitudes. Most 4LAC blazars (98%),...
The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by Large Area Telescope aboard Fermi Gamma-ray Space provide constraints on nature these unique astrophysical sources. GRB had largest fluence, highest-energy photon (95 GeV), longest γ-ray duration (20 hours), and one isotropic energy releases ever observed from a GRB. Temporal spectral analyses challenge widely accepted model that nonthermal high-energy emission in afterglow phase GRBs is synchrotron radiated...
Abstract We present a search for spatial extension in high-latitude ( ) sources recent Fermi point source catalogs. The result is the High-Latitude Extended Sources Catalog, which provides extensions (or upper limits thereof) and likelihood profiles suite of tested morphologies. find 24 extended sources, 19 were not previously characterized as extended. These include that are potentially associated with supernova remnants star-forming regions. also found γ -ray emission vicinity Cen A radio...
Abstract The preliminary detections of the gamma-ray burst 221009A up to 18 TeV by LHAASO and 251 Carpet 2 have been reported through Astronomer’s Telegrams Gamma-ray Coordination Network circulars. Since this is at redshift z = 0.1505, these photons may first seem a low probability avoid pair production off background radiation fields survive reach detectors on Earth. By extrapolating 0.1–1.0 GeV Fermi Large Area Telescope spectrum from higher energies using limit intrinsic burst, we show...
Abstract SIRI-2 is a collection of strontium iodide gamma-ray detectors sensitive at approximately 400 keV to 10 MeV, launched on the Department Defense's STPSat-6 geosynchronous orbit. detected burst (GRB) 221009A and, unlike most GRB detectors, was not saturated and did require any pulse pileup corrections. The energetics this as measured by are consistent with those found other instruments, Band function fits spectra from unsaturated Insight GECAM instruments similar corrected Fermi...
We introduce a methodology for analysis of multiwavelength data from X-ray selected BL Lac (XBL) objects detected in the TeV regime. By assuming that radio--through--X-ray flux XBLs is nonthermal synchrotron radiation emitted by isotropically-distributed electrons randomly oriented magnetic field relativistic blazar jet, we obtain electron spectrum. This spectrum then used to deduce self-Compton (SSC) as function Doppler factor, field, and variability timescale. The timescale infer comoving...
We extend a method for modeling synchrotron and self-Compton radiations in blazar jets to include external Compton (EC) processes. The basic model assumption is that the radio through soft X-ray flux nonthermal radiation emitted by isotropically distributed electrons randomly directed magnetic field of outflowing relativistic jet plasma. Thus, electron distribution given spectrum, depending only on Doppler factor δD mean B, comoving emission region size scale R'b ≲ cδDtv/(1 + z), where tv...
Recent claims that the strength BIGMF of intergalactic magnetic field (IGMF) is ≳ 10−15 G are based on upper limits to expected cascade flux in GeV band produced by blazar TeV photons absorbed extragalactic background light. This limit depends an assumption mean remains constant timescales 2(BIGMF/10−18G)2/(E/10 GeV)2 yr for IGMF coherence length ≈1 Mpc, where E measured photon energy. Restricting activity 1ES 0229+200 ≈3–4 years during which source has been observed leads a more robust...
Fermi has provided the largest sample of γ-ray-selected blazars to date. In this work we use a uniformly selected set 211 BL Lacertae (BL Lac) objects detected by during its first year operation. We obtained redshift constraints for 206 out Lac in our sample, making it and most complete available literature. determine luminosity function evolution with cosmic time. find that classes is positive, space density peaking at modest (z ≈ 1.2). Low-luminosity, high-synchrotron–peaked (HSP) are an...
Gamma rays reveal the Universe's history How many stars have formed in Universe, and when did they do so? These fundamental questions are difficult to answer because there systematic uncertainties converting light we observe into total mass of galaxies. The Fermi-LAT Collaboration addressed these by exploiting way that gamma from distant blazars propagate through intergalactic space, which depends on amount emitted all collaboration found star formation peaked about 3 billion years after Big...
We report Fermi-LAT observations of the radio-loud AGN SBS 0846+513 (z=0.5835), optically classified as a Narrow-Line Seyfert 1 galaxy, together with new and archival radio-to-X-ray data. The source was not active at gamma-ray energies during first two years Fermi operation. A significant increase in activity observed 2010 October-2011 August. In particular strong flare 2011 June reaching an isotropic luminosity (0.1-300 GeV) 1.0x10^48 erg/s, comparable to that brightest flat spectrum radio...
The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe class mission concept that will provide essential contributions to multimessenger astrophysics in the late 2020s and beyond. AMEGO combines high sensitivity 200 keV 10 GeV energy range with wide field of view, good spectral resolution, polarization sensitivity. Therefore, key study astrophysical objects have unique signatures gamma-ray regime, such as neutron star mergers, supernovae, flaring active galactic nuclei....
The diffuse extragalactic background light (EBL) is formed by ultraviolet (UV), optical, and infrared (IR) photons mainly produced star formation processes over the history of Universe, contains essential information about galaxy evolution cosmology. Here, we present a new determination evolving EBL spectral energy distribution using novel approach purely based on data aiming to reduce current uncertainties higher redshifts IR intensities. Our calculations use multiwavelength observations...
The Auger Collaboration reports that the arrival directions of >60 EeV ultra-high energy cosmic rays (UHECRs) cluster along supergalactic plane and correlate with active galactic nuclei (AGN) within ~100 Mpc. association several events nearby radio galaxy Centaurus A supports paradigm UHECRs are powered by supermassive black-hole engines accelerated to energies in shocks formed variable plasma winds inner jets galaxies. GZK horizon length 75 UHECR protons is Mpc, so results consistent an...
Does the "blazar sequence" exist, or is it a result of selection effect, due to difficulty in measuring redshifts blazars with both high synchrotron peak frequencies (\gtrsim 10^{15} Hz) and luminosities 10^{46} erg s^{-1})? We explore this question sample from Second Catalog Active Galactic Nuclei (AGN) Fermi Large Area Telescope (LAT). The Compton dominance, ratio luminosities, essentially redshift-independent quantity, thus crucial answering question. find that correlation exists between...
Fermi Gamma-ray Space Telescope observations of the flat spectrum radio quasar 3C 454.3 show a spectral-index change ΔΓ ≅ 1.2 ± 0.3 at break energy Ebr ≈ 2.4 GeV. Such sharp is inconsistent with cooling electron distribution and poorly fit synchrotron self-Compton model. We that combination two components, namely, Compton-scattered disk broad-line region (BLR) radiations, explains this spectral gives good to quasi-simultaneous radio, optical/UV, X-ray, γ-ray observed in 2008 August. A can be...
The first statistically significant detection of the cosmic \gamma-ray horizon (CGRH) that is independent any extragalactic background light (EBL) model presented. CGRH a fundamental quantity in cosmology. It gives an estimate opacity Universe to very high energy (VHE) photons due photon-photon pair production with EBL. only estimations date are predictions from EBL models and lower limits observations cosmological blazars bursts. Here, we present homogeneous synchrotron/synchrotron...
In this paper we report on the two-year-long Fermi-LAT observation of peculiar blazar 4C +21.35 (PKS 1222+216). This source was in a quiescent state from start science operations Fermi Gamma-ray Space Telescope 2008 August until 2009 September, and then became more active, with gradually increasing flux some moderately-bright flares. 2010 April June, underwent very strong GeV outburst composed several major flares characterized by rise decay timescales order day. During outburst, spectra...
Distant BL Lacertae objects emit $\gamma$ rays which interact with the extragalactic background light (EBL), creating electron-positron pairs, and reducing flux measured by ground-based imaging atmospheric Cherenkov telescopes (IACTs) at very-high energies (VHE). These pairs can Compton-scatter cosmic microwave background, a $\gamma$-ray signature slightly lower observable \fermi\ Large Area Telescope (LAT). This signal is strongly dependent on intergalactic magnetic field (IGMF) strength...
The detection of high-redshift ($z>$3) blazars enables the study evolution most luminous relativistic jets over cosmic time. More importantly, tend to host massive black holes and can be used constrain space density heavy in early Universe. Here, we report first with \fermi-Large Area Telescope five \gm-ray emitting beyond $z=3.1$, more distant than any previously detected $\gamma$-rays. Among these objects, NVSS J151002+570243 is now known blazar at $z=4.31$. These objects have steeply...
The Extragalactic Background Light (EBL) can be probed via the absorption imprint it leaves in spectra of gamma-ray sources ($\gamma\gamma \rightarrow e^-e^+$). We recently developed a dedicated technique to reconstruct EBL, and its evolution with redshift, from $\gamma$ ray optical depth data using large sample blazars detected by $Fermi$ Large Area Telescope. Here, we extend this dataset TeV regime ground-based Cherenkov observations 38 report first homogeneous measurement EBL spectral...