A5019923842- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Advanced Numerical Analysis Techniques
- Mechanics and Biomechanics Studies
- High-pressure geophysics and materials
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Advanced X-ray Imaging Techniques
- Computational Geometry and Mesh Generation
- Computer Graphics and Visualization Techniques
- Adaptive optics and wavefront sensing
- 3D Shape Modeling and Analysis
- Particle Accelerators and Free-Electron Lasers
- Manufacturing Process and Optimization
- Solar and Space Plasma Dynamics
- Astrophysics and Star Formation Studies
- Particle Detector Development and Performance
- Matrix Theory and Algorithms
- Geophysics and Gravity Measurements
- Image Processing and 3D Reconstruction
- Advanced Theoretical and Applied Studies in Material Sciences and Geometry
University of Hertfordshire
2021-2024
University of Cambridge
2012-2024
Howard University
2024
Goddard Space Flight Center
2024
California Institute of Technology
2012-2017
Jet Propulsion Laboratory
2015-2017
Columbia University
2014
University of Manitoba
2004-2013
Institute of Astronomy
2010-2012
Lakehead University
1978-1980
The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 2012 June 13, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates band from 3 to 79 keV, extending sensitivity of far beyond ∼10 keV cutoff achieved by all previous satellites. inherently low background associated with concentrating light enables probe hard sky a more than 100-fold improvement over collimated or coded mask instruments that have operated this bandpass. Using its unprecedented...
ABSTRACT We report the detection of coherent pulsations from ultraluminous X-ray source (ULX) NGC 7793 P13. The ≈0.42 s nearly sinusoidal were initially discovered in broadband observations using XMM-Newton and NuSTAR taken 2016. subsequently also found archival data 2013 2014. significant (≫5 σ ) demonstrates that compact object P13 is a neutron star, given observed peak luminosity ≈10 40 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>erg</mml:mi>...
We present the calibration of Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray satellite. used Crab as primary effective area calibrator and constructed a piece-wise linear spline function to modify vignetting response. The achieved residuals for all off-axis angles energies, compared assumed spectrum, are typically better than ±2% up 40 keV 5%–10% above due limited counting statistics. An empirical adjustment theoretical two-dimensional point-spread (PSF) was found using several strong...
We present an X-ray spectral analysis of a large sample 25 ‘bare’ active galactic nuclei (AGN), sources with little or no complicating intrinsic absorption, observed Suzaku. Our work focuses on studying the potential contribution from relativistic disc reflection and examining implications this interpretation for complexities frequently displayed by AGN in bandpass. During analysis, we take unique approach attempting to simultaneously undertake systematic whole sample, as well detailed...
The evolution of galaxies is connected to the growth supermassive black holes in their centers. During quasar phase, a huge luminosity released as matter falls onto hole, and radiation-driven winds can transfer most this energy back host galaxy. Over five different epochs, we detected signatures nearly spherical stream highly ionized gas broadband x-ray spectra luminous PDS 456. This persistent wind expelled at relativistic speeds from inner accretion disk, its wide aperture suggests an...
Supermassive black holes in the nuclei of active galaxies expel large amounts matter through powerful winds ionized gas. The archetypal galaxy NGC 5548 has been studied for decades, and high-resolution X-ray UV observations have previously shown a persistent outflow. An observing campaign 2013 with six space observatories shows nucleus to be obscured by long-lasting, clumpy stream gas never seen before. It blocks 90% soft emission causes simultaneous deep, broad absorption troughs. outflow...
Abstract We discovered 2.8 s pulsations in the X-ray emission of ultraluminous source (ULX) M51 ULX-7 within UNSEeN project, which was designed to hunt for new pulsating ULXs (PULXs) with XMM-Newton. The pulse shape is sinusoidal, and large variations its amplitude were observed even single exposures (pulsed fraction from less than 5% 20%). Source variable, generally at an luminosity between 10 39 40 erg −1 , located outskirts spiral galaxy M51a a distance 8.6 Mpc. According our analysis,...
A rapidly convergent algorithm is given which will solve <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A'Q + QA = -C</tex> for xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> when xmlns:xlink="http://www.w3.org/1999/xlink">A</tex> a stable matrix. The proposed requires only xmlns:xlink="http://www.w3.org/1999/xlink">4n^{2}</tex> words of memory (for large xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> ) and converges in approximately...
Ultraluminous X-ray sources (ULXs) with luminosities lying between ∼3 × 1039 and 2 1040 erg s−1 represent a contentious sample of objects as their brightness, together lack unambiguous mass estimates for the vast majority central objects, leads to degenerate scenario where accretor could be stellar remnant (black hole or neutron star) intermediate-mass black (IMBH). Recent, high-quality observations imply that presence IMBHs in these is unlikely unless accretion flow somehow deviates...
The only relativistic reflection model that implements a parameter relating the intensity incident on an accretion disk to observed is relxill. used in earlier versions of this model, referred as strength, unsatisfactory, and it has been superseded by provides insight into geometry, namely fraction. fraction defined ratio coronal illuminating reaches observer. relxill combines general ray-tracing code photoionization compute component radiation reflected from illuminated internal source....
We report on observations of NGC1068 with NuSTAR, which provide the best constraints to date its $>10$~keV spectral shape. find no strong variability over past two decades, consistent Compton-thick AGN classification. The combined Chandra, XMM-Newton, and Swift-BAT dataset offers new insights into complex reflected emission. critical combination high signal-to-noise NuSTAR data a spatial decomposition Chandra allow us break several model degeneracies greatly aid physical interpretation. When...
An extensive multi-satellite campaign on NGC 5548 has revealed this archetypal Seyfert-1 galaxy to be in an exceptional state of persistent heavy absorption. Our observations taken 2013-2014 with XMM-Newton, Swift, NuSTAR, INTEGRAL, Chandra, HST and two ground-based observatories have together enabled us establish that unexpected phenomenon is caused by outflowing stream weakly ionised gas (called the obscurer), extending from vicinity accretion disk broad-line region. In work we present...
We present broadband X-ray analyses of a sample bright ultraluminous sources with the goal investigating spectral similarity this population to known ULX pulsars, M82 X-2, NGC7793 P13 and NGC5907 ULX. perform phase-resolved analysis XMM-Newton+NuSTAR dataset ULX, finding that pulsed emission from accretion column in source exhibits similar shape seen both X-2 P13, is responsible for excess observed at highest energies when spectra are fit disk models. then demonstrate 'hard' excesses all...
We report the detection of weak pulsations from archetypal ultraluminous X-ray source (ULX) NGC 1313 X-2. Acceleration searches reveal sinusoidal in segments two out six new deep observations this object, with a period $\sim$ 1.5 s and pulsed fraction 5%. use Monte Carlo simulations to demonstrate that individual detections are unlikely originate false Poisson noise given their very close frequencies; strong similarity other detected ULXs also argues they real. The presence large bubble...
The black hole binary Cygnus X-1 was observed in late-2012 with the Nuclear Spectroscopic Telescope Array (NuSTAR) and Suzaku, providing spectral coverage over ~1-300 keV range. source soft state a multi-temperature blackbody, power-law, reflection components along absorption from highly ionized material system. high throughput of NuSTAR allows for very quality measurement complex iron line region as well rest component. is clearly broadened well-described by relativistic blurring model, an...
Abstract Here we study a 1–200 keV energy spectrum of the black hole binary Cygnus X-1 taken with NuSTAR and Suzaku . This is first report observation Cyg in intermediate state, was during part orbit where absorption due to companion’s stellar wind minimal. The includes multi-temperature thermal disk component, cutoff power-law relativistic nonrelativistic reflection components. Our initial fits publicly available constant density models ( relxill reflionx ) lead extremely high iron...
We present 3-50 keV NuSTAR observations of the AGN Mrk 335 in a very low flux state. The spectrum is dominated by strong features at energies iron line 5-7 and Compton hump from 10-30 keV. source variable during observation, with variability concentrated energies, which suggesting either relativistic reflection or absorption scenario. In this work we focus on interpretation, making use new models that self consistently calculate fraction, blurring angle-dependent for different coronal...
We present simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR ) and Suzaku observations of the X-ray binary Cygnus X-1 in hard state. This is first time this state has been observed Cyg with NuSTAR, which enables us to study reflection broadband spectra unprecedented detail. confirm that iron line cannot be fit a combination narrow lines absorption features, instead requiring relativistically blurred profile from companion wind. use models García et al. simultaneously measure black...
We present the results of NuSTAR and XMM-Newton observations two ultraluminous X-ray sources (ULX) NGC 1313 X-1 X-2. The combined spectral bandpass satellites enables us to produce first spectrum between 0.3 30 keV, while X-2 is not significantly detected by above 10 keV. data demonstrate that has a clear cutoff whose presence was only marginally detectable with previous observations. This rules out interpretation as black hole in standard low/hard state, it deeper than predicted for...