J. H. Buckley
A5031907920- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Radio Astronomy Observations and Technology
- Neutrino Physics Research
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Radiation Detection and Scintillator Technologies
- Atomic and Subatomic Physics Research
- Particle physics theoretical and experimental studies
- Particle Accelerators and Free-Electron Lasers
- Solar and Space Plasma Dynamics
- Cosmology and Gravitation Theories
- Nuclear Physics and Applications
- Astronomy and Astrophysical Research
- Medical Imaging Techniques and Applications
- Astronomical Observations and Instrumentation
- Radiation Therapy and Dosimetry
- Photocathodes and Microchannel Plates
- Advanced Data Storage Technologies
- Parallel Computing and Optimization Techniques
- Stellar, planetary, and galactic studies
- Calibration and Measurement Techniques
- Planetary Science and Exploration
Washington University in St. Louis
2015-2024
Twin Cities Orthopedics
2021-2023
University of Minnesota
2021-2023
Brookings Institution
2021
Columbia University
2019-2021
University of California, Berkeley
2009-2021
Louisiana State University
1999-2021
University of Bridgeport
2021
DePauw University
2019
Obayashi (Japan)
2019
Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build next generation instrument, factor 5-10 improvement sensitivity 100 GeV 10 TeV range extension energies well below above TeV. will consist two arrays (one north, one south) for full sky coverage be operated as open observatory....
The Cherenkov Telescope Array, CTA, will be the major global observatory for very high energy gamma-ray astronomy over next decade and beyond. scientific potential of CTA is extremely broad: from understanding role relativistic cosmic particles to search dark matter. an explorer extreme universe, probing environments immediate neighbourhood black holes voids on largest scales. Covering a huge range in photon 20 GeV 300 TeV, improve all aspects performance with respect current instruments....
We present UBVRI photometry of 44 Type Ia supernovae (SNe Ia) observed from 1997 to 2001 as part a continuing monitoring campaign at the Fred Lawrence Whipple Observatory Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is largest homogeneously reduced sample SNe date, nearly doubling number well-observed, nearby with published multicolor CCD light curves. large U-band unique addition, important connections high redshift. decline rate SN curves...
In this paper, we present the analysis and results of a direct measurement cosmic-ray proton spectrum with CALET instrument onboard International Space Station, including detailed assessment systematic uncertainties. The observation period used in is from October 13, 2015 to August 31, 2018 (1054 days). We have achieved very wide energy range necessary carry out measurements 50 GeV 10 TeV covering, for first time space, single whole interval previously investigated most cases separate...
Following the detection of strong TeV γ-ray flares from BL Lac object 1ES 1959+650 with Whipple 10 m Cerenkov telescope on 2002 May 16 and 17, we performed intensive target opportunity radio, optical, X-ray, observations 18 to August 14. Observations X-ray Rossi X-Ray Timing Explorer HEGRA telescopes revealed several flares, enabling us sensitively test X-ray-γ-ray flux correlation properties. Although fluxes seemed be correlated in general, found an "orphan" flare that was not accompanied...
We have used data from a TeV $\ensuremath{\gamma}$-ray flare associated with the active galaxy Markarian 421 to place bounds on possible energy dependence of speed light in context an effective quantum gravitational scale. Recent theoretical work suggests that such scale could be less than Planck mass and perhaps as low ${10}^{16}$ GeV. The limits derived here indicate this excess $6\ifmmode\times\else\texttimes\fi{}{10}^{16}$ GeV for at least one approach gravity D-brane string theory. To...
The spectrum of gamma rays from the Crab Nebula has been measured in energy range 500 GeV-8 TeV at Whipple Observatory by atmospheric Cerenkov technique. Two methods analysis that were used to derive spectra, order reduce chance calibration errors, gave good agreement, as did observations made with changed equipment several years apart. It is concluded stable and reliable spectra can now be range. represented this power-law fit, J = (3.20 ± 0.17 0.6) × 10-7 (E/1 TeV)-2.49±0.06±0.04 m-2 s-1...
The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles energies exceeding 10^12 electron Volts (eV) and are bright sources very-high-energy (VHE) gamma-ray emission, it not yet known where VHE emission originates. Here we report on radio observations galaxy M87, revealing period extremely strong flares accompanied by increase flux from its nucleus. These results...
We report results from an intensive multiwavelength monitoring campaign on the TeV blazar Mrk 421 over period of 2003-2004. The source was observed simultaneously at energies with Whipple 10 m telescope and X-ray Rossi X-Ray Timing Explorer (RXTE) during each clear night within observing windows. Supporting observations were also frequently carried out optical radio wavelengths to provide simultaneous or contemporaneous coverages. large amount data has allowed us examine variability in...
Recent advances in ground-based gamma ray astronomy have led to the discovery of more than 70 sources very high energy (Eγ ⩾ 100 GeV) rays, falling into a number source populations including pulsar wind nebulae, shell type supernova remnants, Wolf-Rayet stars, giant molecular clouds, binary systems, Galactic Center, active galactic nuclei and 'dark' (yet unidentified) objects. We summarize history TeV up current status field description experimental techniques highlight recent astrophysical...
We present a detailed analysis of week-long simultaneous observations the blazar Mrk 421 at 2-60 keV X-rays (RXTE) and TeV γ-rays (Whipple HEGRA) in 2001. Accompanying optical monitoring was performed with Mt. Hopkins 48 inch telescope. The unprecedented quality this data set enables us to establish existence correlation between X-ray luminosities, also start unveiling some its characteristics, particular energy dependence time variability. source shows strong variations both γ-ray bands,...
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...
LS I +61 303 is one of only a few high-mass X-ray binaries currently detected at high significance in very energy gamma-rays. The system was observed over several orbital cycles (between September 2006 and February 2007) with the VERITAS array imaging air-Cherenkov telescopes. A signal gamma-rays energies above 300 GeV found statistical 8.4 standard deviations. flux measured to be strongly variable; maximum during most apastron. spectrum for period emission can characterized by power law...
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...
We present evidence that the very high energy (VHE, E > 100 GeV) gamma-ray emission coincident with supernova remnant IC 443 is extended. contains one of best studied sites remnant/molecular cloud interaction and pulsar wind nebula CXOU J061705.3+222127, both which are important targets for VHE observations. VERITAS observed 37.9 hr during 2007 detected above 300 GeV an excess 247 events, resulting in a significance 8.3 standard deviations (σ) before trials 7.5σ after point-source search....
First results of a cosmic-ray electron and positron spectrum from 10 GeV to 3 TeV is presented based upon observations with the CALET instrument on International Space Station starting in October, 2015. Nearly half million events are included analysis. an all-calorimetric total vertical thickness 30 ${X}_{0}$ fine imaging capability designed achieve large proton rejection excellent energy resolution well into region. The observed over can be fit single power law spectral index...
We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity 3-79 keV range, revealing that spectrum softens when source is dimmer until X-ray spectral shape saturates into a steep power law with photon index...
We report on the results of a search for γ-ray pair halos with stacking analysis low redshift blazars using data from Fermi Large Area Telescope. For this we used number priori selection criteria, including spatial and spectral properties sources. The angular distribution ~1 GeV photons around 24 stacked isolated high-synchrotron-peaked BL Lacs z<0.5 shows an excess over that pointlike A frequentist test yields p value p~0.01 extended emission against point-source hypothesis. Bayesian...
Searching for axion dark matter, the ADMX Collaboration acquired data from January to October 2018, over mass range 2.81–3.31 μeV, corresponding frequency 680–790 MHz. Using an haloscope consisting of a microwave cavity in strong magnetic field, experiment excluded Dine-Fischler-Srednicki-Zhitnisky (DFSZ) axions at 90% confidence level and 100% matter density this entire range, except few gaps due mode crossings. This paper explains full analysis run 1B, motivating choices informed by...
We study the radio signals generated when an axion star enters magnetosphere of a neutron star. As moves through resonant region where plasma-induced photon mass becomes equal to mass, axions can efficiently convert into photons, giving rise intense, transient signal. show that dense with $\ensuremath{\sim}{10}^{\ensuremath{-}13}\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ composed $\ensuremath{\sim}10\text{ }\ensuremath{\mu}\mathrm{eV}$ account for most mysterious fast bursts.