A. B. Hill
A5073945338- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Dark Matter and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Particle Detector Development and Performance
- Astronomy and Astrophysical Research
- Radio Astronomy Observations and Technology
- High-pressure geophysics and materials
- Geophysics and Gravity Measurements
- Stellar, planetary, and galactic studies
- Particle Accelerators and Free-Electron Lasers
- Particle physics theoretical and experimental studies
- Particle accelerators and beam dynamics
- Galaxies: Formation, Evolution, Phenomena
- Mechanics and Biomechanics Studies
- Solar and Space Plasma Dynamics
- Calibration and Measurement Techniques
- Nuclear Physics and Applications
- Astrophysics and Star Formation Studies
- Neutrino Physics Research
- Planetary Science and Exploration
- Time Series Analysis and Forecasting
- Advanced X-ray Imaging Techniques
University of Southampton
2009-2021
Kavli Institute for Particle Astrophysics and Cosmology
2012-2016
Stanford University
2004-2016
SLAC National Accelerator Laboratory
2003-2016
National Institute for Astrophysics
2008-2013
Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano
2013
Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna
2008-2013
The Ohio State University
2013
Fermi National Accelerator Laboratory
2013
Duke Medical Center
2013
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...
ABSTRACT We present a catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), primary science instrument on Fermi Gamma-ray Space (Fermi) , during first 11 months phase mission, which began 2008 August 4. The First -LAT (1FGL) contains 1451 and characterized in 100 MeV to GeV range. Source detection was based average flux over month period, threshold likelihood Test Statistic is 25, corresponding significance just 4σ. 1FGL includes source location regions,...
This catalog summarizes 117 high-confidence ⩾0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on Fermi satellite. Half are neutron stars discovered LAT through periodicity searches in and radio around unassociated source positions. The pulsars evenly divided into groups: millisecond pulsars, young radio-loud radio-quiet pulsars. We characterize pulse profiles energy spectra derive luminosities when distance information exists. Spectral...
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...
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.,...
We present the first catalog of active galactic nuclei (AGNs) detected by Large Area Telescope (LAT), corresponding to 11 months data collected in scientific operation mode. The First LAT AGN Catalog (1LAC) includes 671 γ-ray sources located at high Galactic latitudes (|b|>10°) that are with a test statistic greater than 25 and associated statistically AGNs. Some multiple AGNs, consequently, 709 comprising 300 BL Lacertae objects, 296 flat-spectrum radio quasars, 41 AGNs other types, 72...
The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of emission towards Galactic centre (GC) in high-energy gamma-rays. This paper describes analysis data taken during first 62 months mission energy range 1-100 GeV from a $15^\circ \times 15^\circ$ region about direction GC, and implications for interstellar emissions produced by cosmic ray (CR) particles interacting with gas radiation fields inner Galaxy point sources detected. Specialised models (IEMs) are...
Dark matter in the Milky Way may annihilate directly into gamma rays, producing a monoenergetic spectral line. Therefore, detecting such signature would be strong evidence for dark annihilation or decay. We search lines Fermi Large Area Telescope observations of halo energy range 200 MeV to 500 GeV using analysis methods from our most recent line searches. The main improvements relative previous works are use 5.8 years data reprocessed with Pass 8 event-level and additional resulting...
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...
In this paper, we report on the fourth soft gamma-ray source catalog obtained with IBIS imager board INTEGRAL satellite. The scientific data set is based more than 70 Ms of high-quality observations performed during first five and a half years Core Program public observations. Compared to previous surveys, includes substantially increased coverage extragalactic fields, comprises 700 high-energy sources detected in energy range 17–100 keV, including both transients faint persistent objects...
ABSTRACT Most of the celestial γ rays detected by Large Area Telescope (LAT) on board Fermi Gamma-ray Space originate from interstellar medium when energetic cosmic interact with nucleons and photons. Conventional point-source extended-source studies rely modeling this diffuse emission for accurate characterization. Here, we describe development Galactic Interstellar Emission Model (GIEM), which is standard adopted LAT Collaboration publicly available. This model based a linear combination...
Weakly interacting massive particles (WIMPs) are a theoretical class of that excellent dark matter candidates. WIMP annihilation or decay may produce essentially monochromatic γ rays detectable by the Fermi Large Area Telescope (LAT) against astrophysical γ-ray emission Galaxy. We have searched for spectral lines in energy range 5–300 GeV using 3.7 years data, reprocessed with updated instrument calibrations and an improved dispersion model compared to previous Fermi-LAT Collaboration line...
We report for the first time a gamma-ray and multi-wavelength nearly-periodic oscillation in an active galactic nucleus. Using Fermi Large Area Telescope (LAT) we have discovered apparent quasi-periodicity flux (E >100 MeV) from GeV/TeV BL Lac object PG 1553+113. The marginal significance of 2.18 +/-0.08 year-period cycle is strengthened by correlated oscillations observed radio optical fluxes, through data collected OVRO, Tuorla, KAIT, CSS monitoring programs Swift UVOT. appearing ~10 years...
We present a catalog of gamma-ray sources at energies above 10 GeV based on data from the Large Area Telescope (LAT) accumulated during first three years Fermi Gamma-ray Space mission. The Fermi-LAT >10GeV (1FHL) has 514 sources. For each source we location, spectrum, measure variability, and associations with cataloged other wavelengths. found that 449 (87%) could be associated known sources, which 393 (76% 1FHL sources) are active galactic nuclei. Of 27 pulsars, find 20 (12) to have...
We present radio and γ-ray observations, which, along with concurrent X-ray reveal that the binary millisecond pulsar (MSP)/low-mass transition system PSR J1023+0038 has undergone a transformation in state. Whereas until recently harbored bright pulsar, pulsations at frequencies between 300 to 5000 MHz have now become undetectable. Concurrent this disappearance, flux of quintupled. conclude that, though is currently not detectable, mechanism still active wind, as well newly formed accretion...
In this paper we report on the third soft gamma-ray source catalog obtained with IBIS/ISGRI imager board INTEGRAL satellite. The scientific data set is based more than 40 Ms of high-quality observations performed during first 3.5 yr Core Program and public observations. Compared to previous surveys, includes a substantially increased coverage extragalactic fields, comprises 400 high-energy sources detected in energy range 17-100 keV, including both transients faint persistent objects that...
Microquasar Spotted Microquasars are binary star systems where a normal sheds matter onto neutron or black hole, generating x-ray radiation and jets of material moving at relativistic speeds. have proved difficult to detect in high-energy gamma rays (> 100 megaelectron volts). Using the Fermi Large Area Telescope, Abdo et al. (p. 1512 , published online 26 November; see Perspective by Bignami ) now report detection variable gamma-ray emission from microquasar Cygnus X-3. The flux is...
Pulsar systems accelerate particles to immense energies. The detailed functioning of these engines is still poorly understood, but polarization measurements high-energy radiation may allow us locate where the are accelerated. We have detected polarized gamma rays from vicinity Crab pulsar using data spectrometer on International Gamma-Ray Astrophysics Laboratory satellite. Our results show with an electric vector aligned spin axis neutron star, demonstrating that a substantial fraction...
Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from companion star. Current physical models posit that shocked expanding gas the nova shell can produce X-ray emission but at higher energies has not been widely expected. Here, we report Fermi Large Area Telescope detection of variable gamma-ray (0.1-10 GeV) recently-detected optical symbiotic star V407 Cygni. We propose material interacts with dense ambient medium red giant primary, and particles be...
Supergiant high-mass X-ray binaries (SGXBs) are believed to be rare objects, as stars in the supergiant phase have a very short lifetime and date only about dozen of them been discovered. They known persistent bright sources. INTEGRAL is changing this classical picture, its observations revealing presence new subclass SGXBs that labeled fast transients (SFXTs), since they strongly characterized by outbursts lasting less than day, typically few hours. We report on IBIS detections newly...
ABSTRACT To uniformly determine the properties of supernova remnants (SNRs) at high energies, we have developed first systematic survey energies from 1 to 100 GeV using data Fermi Large Area Telescope (LAT). Based on spatial overlap sources detected with SNRs known radio surveys, classify 30 as likely SNRs. We also report 14 marginal associations and 245 flux upper limits. A mock catalog in which positions are scrambled Galactic longitude allows us an limit 22% number candidates falsely...
This Letter presents the first results from observations of LSI +61 303 using Large Area Telescope data Fermi Gamma-Ray Space between 2008 August and 2009 March. Our indicate variability that is consistent with binary period, emission being modulated at 26.6 +/- 0.5 days. constitutes detection orbital periodicity in high-energy gamma rays (20 MeV-100 GeV, HE). The light curve characterized by a broad peak after periastron, as well smaller just before apastron. spectrum best represented power...
The Fermi Large Area Telescope First Source Catalog (1FGL) provided spatial, spectral, and temporal properties for a large number of gamma-ray sources using uniform analysis method. After correlating with the most-complete catalogs source types known to emit gamma rays, 630 these are "unassociated" (i.e. have no obvious counterparts at other wavelengths). Here, we employ two statistical analyses primary characteristics unassociated in an effort correlate their AGN pulsar populations 1FGL....
We report here an all-sky soft gamma-ray source catalog based on IBIS observations performed during the first 1000 orbits of INTEGRAL. The database for construction list consists all good quality data available from launch in 2002 up to end 2010. This corresponds $\sim$110 Ms scientific public with a concentrated coverage Galactic Plane and extragalactic deep exposures. new includes 939 sources above 4.5 sigma significance threshold detected 17-100 keV energy band, which 120 represent...
Pulsar wind nebulae (PWNe) have been established as the most populous class of TeV gamma-ray emitters. Since launch, Fermi Large Area Telescope (LAT)identified five high-energy (100MeV <E< 100 GeV) sources PWNe, and detected a large number PWNe candidates, all powered by young energetic pulsars. The wealth multi-wavelength data available new results provided Fermi-LAT give us an opportunity to find explore radiative processes taking place in known ones. unidentifiedsources (UNIDs) are best...