A5011812851- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Radio Astronomy Observations and Technology
- Particle Accelerators and Free-Electron Lasers
- Dark Matter and Cosmic Phenomena
- Astro and Planetary Science
- Particle Detector Development and Performance
- Nuclear Physics and Applications
- Solar and Space Plasma Dynamics
- Neutrino Physics Research
- Stellar, planetary, and galactic studies
- SAS software applications and methods
- Pulsars and Gravitational Waves Research
- Scientific Measurement and Uncertainty Evaluation
- Genetic and Environmental Crop Studies
- Legume Nitrogen Fixing Symbiosis
- Soybean genetics and cultivation
- Particle accelerators and beam dynamics
- X-ray Spectroscopy and Fluorescence Analysis
- Particle physics theoretical and experimental studies
- CCD and CMOS Imaging Sensors
University of Tasmania
2022-2024
European Space Research and Technology Centre
1993-2006
European Space Astronomy Centre
2006
National Institute of Astrophysics, Optics and Electronics
1996
University of Leicester
1992-1993
University of New Hampshire at Manchester
1993
University College London
1986-1987
Imperial College London
1986
GRB 990123 was the first burst from which simultaneous optical, X-ray, and gamma-ray emission detected; its afterglow has been followed by an extensive set of radio, X-ray observations. We have studied itself as observed Compton Gamma Ray Observatory detectors. find that fluxes are not correlated with optical observations spectra cannot be extrapolated simply to fluxes. The is well fitted standard four-parameter function, exception excess compared this function below ~15 keV during some time...
view Abstract Citations (195) References (85) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The X-Ray Spectra of High-Luminosity Active Galactic Nuclei Observed by Ginga Williams, O. R. ; Turner, M. J. L. Stewart, G. C. Saxton, D. Ohashi, T. Makishima, K. Kii, Inoue, H. Makino, F. Hayashida, Koyama, Results are presented on the X-ray emission from 13 objects, observed as part a spectral survey bright quasars in energy range 2-20 keV. distribution power-law...
The seeds of wild pea (
view Abstract Citations (73) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-Ray Outburst of the Quasar 3C 279 Makino, F. ; Kii, T. Hayashida, K. Inoue, H. Tanaka, Y. Ohashi, Makishima, Awaki, Koyama, Turner, M. J. L. Williams, O. R. A large X-ray flare-up quasar 279, coinciding with an unusual multifrequency outburst, was detected astronomy satellite Ginga. Observations carried out on two occasions (1987 June and 1988 July) indicate that...
Context.GRB 041219a is the brightest burst localised by INTEGRAL. The peak flux of 43 ph cm-2 s-1 ( erg s-1, 20 keV–8 MeV, 1 s integration) greater than that for ~98% all bursts and T90 duration ~186 (~20 MeV) longer but a small number bursts. intense occurred about ~250 after precursor long delay enabled optical near infrared telescopes to observe prompt emission.
We present a catalog of X-ray sources observed during slew maneuvers by the Medium Energy Detector Array onboard EXOSAT Observatory. The slew-survey (EXMS) provides unique record 1-8 keV sky between 1983 and 1986. 98% was observed, with 85% receiving an exposure >60 s. 1210 were detected. By comparing these source positions other catalogs, identifications are given for 992 detections (82% sample). These consist 250 distinct objects, including 95 different binary systems, 14 AGN. A further 58...
We present results from the spectral analysis of EXOSAT data on 31 quasars, 18 radio-loud and 13 radio-quiet. Simple power-law models with fixed (Galactic) absorption give acceptable fits to spectra obtained in 2–10 keV band. Using these we have compared distributions indices α for radio-quiet quasars sample. find that X-ray spectrum is flatter |$\overline\alpha = 0.66\pm 0.07$|, consistent a single index objects. The group, however, shows steeper average spectrum, 0.90\pm 0.11$|, wider...
Abstract Change in phenology has been an important component crop evolution, and selection for earlier flowering through a reduction environmental sensitivity helped broaden adaptation many species. Natural variation domesticated pea (Pisum sativum L.) noted studied decades, but there no clear account of change relative to its wild progenitor. Here we examined the genetic control differences time between P. ssp. humile typical late-flowering photoperiodic s. accession recombinant inbred...
view Abstract Citations (37) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS GINGA Observations of the Dipping Low-Mass X-Ray Binaries XB 1916-053 and EXO 0748-676 Smale, Alan P. ; Mukai, Koji Williams, O. R. Jones, Mark H. Corbet, Robin D. Ginga observations 0748-676, low-mass X-ray binaries with pronounced dips variable depth duration in their light curves, are reported. Periodicity studies XB-1916-053 show results consistent those from...
The results of a GINGA X-ray observation the eclipsing intermediate polar system EX Hya are presented. These new data probe characteristics 67-min modulation and 98-min orbital eclipses at higher energies than was possible with EXOSAT. average fractional depth eclipse goes up increasing energy between 1.5 4 keV. Above keV, is consistent constant level |$\sim 40-50$| per cent. Conversely, pulse fraction rotational decreases in 1.5–6 keV range, but tends to value about 9–10 cent above 6 keV;...
LE and ME spectra of 12 quasars from the EXOSAT data base have been analysed in a search for soft excesses. We able to quantify excesses more accurately by using spectral indices taken much sensitive Ginga observations same quasars. Eight show significant excess remaining four upper limits consistent with ubiquity our sample. establish variability three timescales inner region an accretion disc around 108-M⊙ black hole. The luminosity correlates well other wavebands above MB = – 23, but most...
On January 6th 2004, the IBAS burst alert system triggered 8th gamma-ray (GRB) to be located by INTEGRAL satellite. The position was determined and publicly distributed within 12 s, prompting ESA's XMM-Newton execute a ToO observation just 5 h later, during which an X-ray afterglow detected. GRB had duration ~52 s with two distinct pulses separated ~42 s. Here we present results of imaging spectral analyses prompt emission from data data. γ-ray spectrum is consistent single power-law photon...
view Abstract Citations (36) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-Ray Continuum and Evidence for an Iron Emission Line from the Quasar E1821+643 Kii, T. ; Williams, O. R. Ohashi, Awaki, H. Hayashida, K. Inoue, Kondo, Koyama, Makino, F. Makishima, Saxton, D. Stewart, G. C. Takano, S. Tanaka, Y. Turner, M. J. L. The high-luminosity radio-quiet quasar has been observed with Ginga. 2-10 keV spectrum a power-law energy index, α, of...
We present results from the first holographic bubble chamber experiment. Using topological information on events observed in heavy liquid HOBC, we have determined a total charm pair production cross section of (24.6-8.3+12.0) μb and (3.9-1.9+2.5) 360 GeV/c 200 proton-nucleon interactions respectively. For these estimates assumed linear dependence atomic number A.
Large-scale imaging surveys have grown about 1000 times faster than the number of astronomers in last 3 decades. Using Artificial Intelligence instead astronomer's brains for interpretative tasks allows to keep up with data. We give a progress report on using Convolutional Neural Networks (CNNs) classify three classes rare objects (galaxy mergers, strong gravitational lenses and asteroids) Kilo-Degree Survey (KiDS) Euclid Survey.
We report the first unambiguous detection of X-ray emission from cluster galaxies surrounding radio-quiet QSO E1821 + 643. ROSAT PSPC observations show that is highly luminous, Lx∼ 1045 erg s−1 as would be expected high Abell richness class ( ≥ 2) seen in optical studies. The to contribute an iron line apparent equivalent width 20–142 eV integrated spectrum.
The Compton Gamma-Ray Observatory (CGRO) experiments EGRET and COMPTEL observed the Virgo sky region continuously for 7 weeks between December 10, 1996 January 28, 1997. prominent quasar 3C~273 was found to be brightest source in gamma-rays significantly detected by COMPTEL. experiment a time-variable flux at energies above 100 MeV, which reached 2-week flaring period (December 30, 14, 1997) its highest level during CGRO-era. COMPTEL, however, does not observe obvious time variability below...
Ginga observations of the LMXB X 1822-371 show that broad orbital modulation and eclipse are deeper at higher energies. This is explained if X-ray emitting corona produces softer emission greater heights from disc plane, which suggests either optically thick, or illuminating X-rays anisotropic. Further investigation hampered by an inadequate understanding spectrum
The COMPTEL experiment aboard CGRO, exploring the previously unknown sky at MeV-energies, has so far detected 10 Active Galactic Nuclei (AGN): 9 blazars and radio galaxy Centaurus A. No Seyfert been found yet. With these results opened field of extragalactic Gamma-ray astronomy in MeV-band.
We report results of observations and analyses on the γ-ray blazar PKS 1622-297, with emphasis COMPTEL data (0.75–30 MeV) collected between April 1991 November 1997. 1622-297 was detected as a source γ-rays by EGRET experiment aboard CGRO in 1995 during outburst at energies above 100 MeV lasting for five weeks. In this time period significantly (~5.9 σ) 10–30 MeV. At lower detection is marginal, resulting hard spectrum. The combined COMPTEL/EGRET energy spectrum shows break energies....