J. S. Perkins
A5069698133- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Particle Detector Development and Performance
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Radiation Detection and Scintillator Technologies
- Neutrino Physics Research
- CCD and CMOS Imaging Sensors
- Advanced Semiconductor Detectors and Materials
- Particle physics theoretical and experimental studies
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
- Spacecraft Design and Technology
- Advanced X-ray and CT Imaging
- Galaxies: Formation, Evolution, Phenomena
- Nuclear Physics and Applications
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Planetary Science and Exploration
- Particle accelerators and beam dynamics
- Scientific Research and Discoveries
Goddard Space Flight Center
2015-2024
Nagoya University
2023
Argonne National Laboratory
2023
University of America
2023
Catholic University of America
2021-2023
Hiroshima University
2023
Karlsruhe Institute of Technology
2023
Deleted Institution
2011-2022
University of the Virgin Islands
2019-2021
University of Delaware
2008-2021
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 bubbles are two large structures in the gamma-ray sky extending to 55° above and below Galactic center. We analyze 50 months of Large Area Telescope data between 100 MeV 500 GeV 10° latitude derive spectrum morphology bubbles. thoroughly explore systematic uncertainties that arise when modeling diffuse emission through separate approaches. is well described by either a log parabola or power law with an exponential cutoff. exclude simple more than 7σ significance. cutoff has index...
The light emitted by stars and accreting compact objects through the history of Universe is encoded in intensity extragalactic background (EBL). Knowledge EBL important to understand nature star formation galaxy evolution, but direct measurements are lim- ited Galactic other foreground emissions. Here we report an absorption feature seen combined spectra a sample gamma-ray blazars out redshift z$\sim$1.6. This caused attenuation gamma rays at optical UV frequencies, allowed us measure flux...
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.
Fermipy is an open-source python framework that facilitates analysis of data collected by the Fermi Large Area Telescope (LAT). built on Science Tools, publicly available software suite provided NASA for LAT mission. provides a high-level interface analyzing in simple and reproducible way. The current feature set includes methods extracting spectral energy distributions lightcurves, generating test statistic maps, finding new source candidates, fitting position extension. leverages...
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...
The Fermi Large Area Telescope (LAT) light curve repository (LCR) is a publicly available, continually updated library of gamma-ray curves variable Fermi-LAT sources generated over multiple timescales. LCR aims to provide publication-quality binned on timescales 3 days, 7 and 30 days for 1525 deemed in the source catalog first 10 years observations. consists through full likelihood analyses that model surrounding region, providing fluxes photon indices each time bin. intended as resource...
This detection constrains the mechanism and emission region of gamma-ray radiation in pulsar’s magnetosphere.
A classical nova results from runaway thermonuclear explosions on the surface of a white dwarf that accretes matter low-mass main-sequence stellar companion. In 2012 and 2013, three novae were detected in gamma rays stood contrast to first gamma-ray V407 Cygni 2010, which belongs rare class symbiotic binary systems. Despite likely differences compositions masses their progenitors, are similarly characterized as soft spectrum transient sources over 2-3 week durations. The detections point...
We report the discovery of TeV gamma-ray emission from Type Ia supernova remnant (SNR) G120.1+1.4, known as Tycho's remnant. Observations performed in period 2008-2010 with VERITAS ground-based observatory reveal weak coming direction remnant, compatible a point source located at $00^{\rm h} \ 25^{\rm m} 27.0^{\rm s},\ +64^{\circ} 10^{\prime} 50^{\prime\prime}$ (J2000). The photon spectrum measured by can be described power-law $dN/dE = C(E/3.42\;\textrm{TeV})^{-\Gamma}$ $\Gamma 1.95 \pm...
The Fermi Large Area Telescope (LAT) Collaboration has recently released a catalog of 360 sources detected above 50 GeV (2FHL). This was obtained using 80 months data re-processed with Pass 8, the newest event-level analysis, which significantly improves acceptance and angular resolution instrument. Most 2FHL at high Galactic latitude are blazars. Using detailed Monte Carlo simulations, we measure, for first time, source count distribution, dN/dS, extragalactic γ-ray E>50 find that it is...
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 on TeV γ-ray observations of the blazar Mrk 421 (redshift 0.031) with VERITAS observatory and Whipple 10 m Cherenkov telescope. The excellent sensitivity allowed us to sample fluxes energy spectra unprecedented accuracy where was detected in each pointings. A total 47.3 hr 96 data were acquired between 2006 January 2008 June. present results a study as function time for different flux levels. On May 2 3, bright flares reaching level Crab. complemented radio, optical, X-ray...
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...
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...
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...
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 All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) is designed to identify and characterize gamma rays from extreme explosions accelerators. main science themes include: supermassive black holes their connections neutrinos cosmic rays; binary neutron star mergers the relativistic jets they produce; ray particle acceleration sources including Galactic supernovae; continuous monitoring of other astrophysical events over full sky in this important energy range. AMEGO-X will...
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...
The VERITAS array of Cherenkov telescopes has carried out a deep observational program on the nearby dwarf spheroidal galaxy Segue 1. We report results nearly 48 hours good quality selected data, taken between January 2010 and May 2011. No significant $\ensuremath{\gamma}$-ray emission is detected at nominal position 1, upper limits integrated flux are derived. According to recent studies, 1 most dark matter-dominated currently known. derive stringent bounds various annihilating decaying...