Bio
I am a research scientist, astronomer and astrophysicist in the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University. My research focuses on how material spiralling into a supermassive black hole in the centre of a galaxy is able to release huge amounts of energy, powering some of the brightest objects we see in the Universe.
My research bridges the divide between observational and theoretical studies of black holes, using state of the art space telescopes, developing novel data analysis techniques and designing computer simulations of how light travels around black holes. I am using the X-rays that are emitted and measurements of how they reflect off of the material in its final moments before it falls in to create a 3D map of the extreme environment just outside the event horizon. I am interested in what happens to material and light just before it is lost into the black hole, how the corona that produces the radiation we see is powered, and how black holes are able to launch jets at almost the speed of light.
I am passionate about teaching and communicating science to the general public. I regularly give public lectures to a wide variety of audiences and am the founder and host of the Discover Our Universe public lecture series from Stanford's Kavli Institute of Particle Astrophysics and Cosmology. I have made a number of appearances on TV and radio, and am actively involved in a number of initiatives to involve the public in astronomy and physics.
Honors & Awards
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Einstein Fellowship, NASA (Oct 2016 - Oct 2019)
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Kavli Fellowship, Stanford University (Oct 2019 - Oct 2020)
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National Fellowship, Canadian Institute for Theoretical Astrophysics (CITA) (Sept 2013 - Sept 2015)
Education & Certifications
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Doctor of Philosophy, University of Cambridge, Astronomy (2013)
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Master of Arts, University of Cambridge (2012)
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Master of Natural Sciences, University of Cambridge, Physics (2009)
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Bachelor of Arts, University of Cambridge, Natural Sciences (2009)
Professional Affiliations and Activities
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Fellow, Royal Astronomical Society (2011 - Present)
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Full Member, American Astronomical Society (2013 - Present)
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Member, NASA/US Wide Field Imager Consortium for the ESA Athena Mission (2017 - Present)
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Guest Scientist, JAXA/NASA Xrism Science Team (2022 - Present)
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AGN Science Lead, HEX-P Mission Proposal Team (2022 - Present)
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Member, NASA STROBE-X Mission Study Team (2018 - Present)
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Member, JAXA Hitomi Science Working Group (2014 - 2016)
All Publications
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Wavelet spectral timing: X-ray reverberation from a dynamic black hole corona hidden beneath ultrafast outflows
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2023; 526 (3): 3441-3460
View details for DOI 10.1093/mnras/stad2936
View details for Web of Science ID 001083991100008
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Acceleration and cooling of the corona during X-ray flares from the Seyfert galaxy I Zw 1
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2022; 512 (1): 761-775
View details for DOI 10.1093/mnras/stac416
View details for Web of Science ID 000769650000010
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Reducing the background in X-ray imaging detectors via machine learning
SPIE-INT SOC OPTICAL ENGINEERING. 2022
View details for DOI 10.1117/12.2629496
View details for Web of Science ID 000865607100159
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Light bending and X-ray echoes from behind a supermassive black hole
NATURE
2021; 595 (7869): 657-+
Abstract
The innermost regions of accretion disks around black holes are strongly irradiated by X-rays that are emitted from a highly variable, compact corona, in the immediate vicinity of the black hole1-3. The X-rays that are seen reflected from the disk4, and the time delays, as variations in the X-ray emission echo or 'reverberate' off the disk5,6, provide a view of the environment just outside the event horizon. I Zwicky 1 (I Zw 1) is a nearby narrow-line Seyfert 1 galaxy7,8. Previous studies of the reverberation of X-rays from its accretion disk revealed that the corona is composed of two components: an extended, slowly varying component extending over the surface of the inner accretion disk, and a collimated core, with luminosity fluctuations propagating upwards from its base, which dominates the more rapid variability9,10. Here we report observations of X-ray flares emitted from around the supermassive black hole in I Zw 1. X-ray reflection from the accretion disk is detected through a relativistically broadened iron K line and Compton hump in the X-ray emission spectrum. Analysis of the X-ray flares reveals short flashes of photons consistent with the re-emergence of emission from behind the black hole. The energy shifts of these photons identify their origins from different parts of the disk11,12. These are photons that reverberate off the far side of the disk, and are bent around the black hole and magnified by the strong gravitational field. Observing photons bent around the black hole confirms a key prediction of general relativity.
View details for DOI 10.1038/s41586-021-03667-0
View details for Web of Science ID 000678820500006
View details for PubMedID 34321670
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Low-frequency X-ray timing with Gaussian processes and reverberation in the radio-loud AGN 3C 120
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2019; 489 (2): 1957–72
View details for DOI 10.1093/mnras/stz2269
View details for Web of Science ID 000489298100035
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The high energy X-ray probe (HEX-P): science overview
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
2024; 11
View details for DOI 10.3389/fspas.2024.1471585
View details for Web of Science ID 001372206200001
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A View of the Long-term Spectral Behavior of Ultracompact X-Ray Binary 4U 0614+091
ASTROPHYSICAL JOURNAL
2024; 975 (1)
View details for DOI 10.3847/1538-4357/ad794d
View details for Web of Science ID 001341346200001
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Advancing Precision Particle Background Estimation for Future X-Ray Missions: Correlated Variability between the Alpha Magnetic Spectrometer and Chandra/XMM-Newton
ASTROPHYSICAL JOURNAL
2024; 970 (1)
View details for DOI 10.3847/1538-4357/ad47c6
View details for Web of Science ID 001268658300001
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The outflowing ionised gas of I Zw 1 observed by HST COS
ASTRONOMY & ASTROPHYSICS
2024; 686
View details for DOI 10.1051/0004-6361/202449544
View details for Web of Science ID 001244461900008
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The high energy X-ray probe (HEX-P): probing the physics of the X-ray corona in active galactic nuclei
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
2024; 10
View details for DOI 10.3389/fspas.2023.1308056
View details for Web of Science ID 001144545800001
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Fast, low-noise image sensor technology for strategic X-ray astrophysics missions
SPIE-INT SOC OPTICAL ENGINEERING. 2024
View details for DOI 10.1117/12.3019193
View details for Web of Science ID 001338129600045
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Continued developments in X-ray speed reading: fast, low noise readout for next-generation wide-field imagers
SPIE-INT SOC OPTICAL ENGINEERING. 2024
View details for DOI 10.1117/12.3018198
View details for Web of Science ID 001322667300052
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Demonstrating sub-electron noise performance in Single electron Sensitive Readout (SiSeRO) devices
SPIE-INT SOC OPTICAL ENGINEERING. 2024
View details for DOI 10.1117/12.3020855
View details for Web of Science ID 001322667300037
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X-ray speed reading with the MCRC: prototype success and next generation upgrades
SPIE-INT SOC OPTICAL ENGINEERING. 2024
View details for DOI 10.1117/12.3019147
View details for Web of Science ID 001322667300018
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Towards efficient machine-learning-based reduction of the cosmic-ray induced background in X-ray imaging detectors: increasing context awareness
SPIE-INT SOC OPTICAL ENGINEERING. 2024
View details for DOI 10.1117/12.3020598
View details for Web of Science ID 001338129600047
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X-Ray/UVOIR Frequency-resolved Time Lag Analysis of Mrk 335 Reveals Accretion Disk Reprocessing
ASTROPHYSICAL JOURNAL
2023; 954 (1)
View details for DOI 10.3847/1538-4357/ace77b
View details for Web of Science ID 001052477600001
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UV-Optical Disk Reverberation Lags despite a Faint X-Ray Corona in the Active Galactic Nucleus Mrk 335
ASTROPHYSICAL JOURNAL
2023; 947 (2)
View details for DOI 10.3847/1538-4357/acbcd3
View details for Web of Science ID 000973012600001
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Reduction of cosmic-ray induced background in astronomical X-ray imaging detectors via image segmentation methods
SPIE-INT SOC OPTICAL ENGINEERING. 2023
View details for DOI 10.1117/12.2677095
View details for Web of Science ID 001259432500010
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X-Ray Reverberation Mapping of Ark 564 Using Gaussian Process Regression
ASTROPHYSICAL JOURNAL
2022; 939 (2)
View details for DOI 10.3847/1538-4357/ac978f
View details for Web of Science ID 000884675100001
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A deep, multi-epoch <i>Chandra</i> HETG study of the ionized outflow from NGC 4051
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2022; 516 (4): 5027-5051
View details for DOI 10.1093/mnras/stac2389
View details for Web of Science ID 000860850700006
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The multi-epoch X-ray tale of I Zwicky 1 outflows
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2022; 516 (4): 5171-5186
View details for DOI 10.1093/mnras/stac2552
View details for Web of Science ID 000860850700016
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Mitigating the effects of particle background on the Athena Wide Field Imager
JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS
2022; 8 (1)
View details for DOI 10.1117/1.JATIS.8.1.018001
View details for Web of Science ID 000780829700049
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First results on SiSeRO devices: a new x-ray detector for scientific instrumentation
Journal of Astronomical Telescopes, Instruments, and Systems
2022; 8 (2): 12
View details for DOI 10.1117/1.JATIS.8.2.026006
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Single electron Sensitive Readout (SiSeRO) X-ray detectors: Technological progress and characterization
SPIE-INT SOC OPTICAL ENGINEERING. 2022
View details for DOI 10.1117/12.2629050
View details for Web of Science ID 000860926800021
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Modeling the Multiwavelength Variability of Mrk 335 Using Gaussian Processes
ASTROPHYSICAL JOURNAL
2021; 914 (2)
View details for DOI 10.3847/1538-4357/abfa9f
View details for Web of Science ID 000668209400001
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Identifying charged particle background events in X-ray imaging detectors with novel machine learning algorithms
SPIE-INT SOC OPTICAL ENGINEERING. 2021
View details for DOI 10.1117/12.2562354
View details for Web of Science ID 000674737700039
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Characterizing continuum variability in the radio-loud narrow-line Seyfert 1 galaxy IRAS 17020+4544
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2020; 496 (3): 3708–24
View details for DOI 10.1093/mnras/staa1735
View details for Web of Science ID 000574919300070
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Venturing beyond the ISCO: detecting X-ray emission from the plunging regions around black holes
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2020; 493 (4): 5532–50
View details for DOI 10.1093/mnras/staa628
View details for Web of Science ID 000539094400070
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Blueshifted absorption lines from X-ray reflection in IRAS 13224-3809
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2020; 493 (2): 2518–22
View details for DOI 10.1093/mnras/staa482
View details for Web of Science ID 000525996700073
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The soft state of the black hole transient source MAXI J1820+070: emission from the edge of the plunge region?
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2020; 493 (4): 5389–96
View details for DOI 10.1093/mnras/staa564
View details for Web of Science ID 000539094400058
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Characterization of the Particle-induced Background of XMM-Newton EPIC-pn: Short- and Long-term Variability
ASTROPHYSICAL JOURNAL
2020; 891 (1)
View details for DOI 10.3847/1538-4357/ab698a
View details for Web of Science ID 000537773700001
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A dynamic black hole corona in an active galaxy through X-ray reverberation mapping
NATURE ASTRONOMY
2020
View details for DOI 10.1038/s41550-019-1002-x
View details for Web of Science ID 000508323100003
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Identifying charged particle background events in x-ray imaging detectors with novel machine learning algorithms
Astronomical Telescopes and Instrumentation, Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray
2020
View details for DOI 10.1117/12.2562354
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Returning radiation in strong gravity around black holes: reverberation from the accretion disc
Monthly Notices of the Royal Astronomical Society
2020; 498 (3): 3302-3319
View details for DOI 10.1093/mnras/staa2566
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Black hole magnetosphere with small-scale flux tubes - II. Stability and dynamics
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2019; 487 (3): 4114–27
View details for DOI 10.1093/mnras/stz1599
View details for Web of Science ID 000478053200085
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The XMM-Newton/HST View of the Obscuring Outflow in the Seyfert Galaxy Mrk 335 Observed at Extremely Low X-Ray Flux
ASTROPHYSICAL JOURNAL
2019; 875 (2)
View details for DOI 10.3847/1538-4357/ab125a
View details for Web of Science ID 000465974900019
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Black hole magnetosphere with small-scale flux tubes
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2019; 484 (4): 4920–32
View details for DOI 10.1093/mnras/stz332
View details for Web of Science ID 000462414400035
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Evidence for an emerging disc wind and collimated outflow during an X-ray flare in the narrow-line Seyfert 1 galaxy Mrk 335
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2019; 484 (3): 4287-4297
View details for DOI 10.1093/mnras/stz274
View details for Web of Science ID 000462410300103
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US Contributions to the Athena Wide Field Imager
SPIE-INT SOC OPTICAL ENGINEERING. 2019
View details for DOI 10.1117/12.2528532
View details for Web of Science ID 000511172300026
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The remarkable X-ray variability of IRAS 13224-3809-I. The variability process
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2019; 482 (2): 2088-2106
View details for DOI 10.1093/mnras/sty2527
View details for Web of Science ID 000454578700048
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Detection of polarized gamma-ray emission from the Crab nebula with the Hitomi Soft Gamma-ray Detector
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (6)
View details for DOI 10.1093/pasj/psy118
View details for Web of Science ID 000456072300015
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The variability of the warm absorber in I Zwicky 1 as seen by XMM-Newton
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2018; 480 (2): 2334-2342
View details for DOI 10.1093/mnras/sty1938
View details for Web of Science ID 000449614800070
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Eleven years of monitoring the Seyfert 1 Mrk 335 with Swift: Characterizing the X-ray and UV/optical variability
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2018; 478 (2): 2557-2568
View details for DOI 10.1093/mnras/sty1134
View details for Web of Science ID 000439547400084
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The 1.5Ms observing campaign on IRAS 13224-3809-I. X-ray spectral analysis
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2018; 477 (3): 3711-3726
View details for DOI 10.1093/mnras/sty836
View details for Web of Science ID 000433893700063
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Variable blurred reflection in the narrow-line Seyfert 1 galaxy Mrk 493
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2018; 477 (3): 3247-3256
View details for DOI 10.1093/mnras/sty828
View details for Web of Science ID 000433893700028
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Hitomi X-ray observation of the pulsar wind nebula G21.5-0.9
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (3)
View details for DOI 10.1093/pasj/psy027
View details for Web of Science ID 000439655600009
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Hitomi X-ray studies of Giant Radio Pulses from the Crab pulsar.
Publications of the Astronomical Society of Japan. Nihon Tenmon Gakkai
2018; 70 (2)
Abstract
To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2 - 300 keV band and the Kashima NICT radio observatory in the 1.4 - 1.7 GHz band with a net exposure of about 2 ks on 25 March 2016, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1,000 and 100 GRPs were simultaneously observed at the main and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main or inter-pulse phases. All variations are within the 2 sigma fluctuations of the X-ray fluxes at the pulse peaks, and the 3 sigma upper limits of variations of main- or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2 - 300 keV band. The values become 25% or 110% for main or inter-pulse GRPs, respectively, when the phase width is restricted into the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.5-10 keV and the 70-300 keV are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of main- and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) ×10-11 erg cm-2, respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magnetosphere and the number of photon-emitting particles temporally increases. However, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a > 0.02% brightening of the pulse-peak flux under such conditions.
View details for DOI 10.1093/pasj/psx083
View details for PubMedID 32020916
View details for PubMedCentralID PMC6999749
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Hitomi (ASTRO-H) X-ray Astronomy Satellite
JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS
2018; 4 (2)
View details for DOI 10.1117/1.JATIS.4.2.021402
View details for Web of Science ID 000439235200002
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Is there a UV/X-ray connection in IRAS 13224-3809?
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2018; 475 (2): 2306–13
View details for DOI 10.1093/mnras/sty008
View details for Web of Science ID 000427345900058
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Hitomi observations of the LMC SNR N 132 D: Highly redshifted X-ray emission from iron ejecta
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (2)
View details for DOI 10.1093/pasj/psx151
View details for Web of Science ID 000432287600008
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Temperature structure in the Perseus cluster core observed with Hitomi
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (2)
View details for DOI 10.1093/pasj/psy004
View details for Web of Science ID 000432287600003
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Hitomi observation of radio galaxy NGC 1275: The first X-ray microcalorimeter spectroscopy of Fe-K alpha line emission from an active galactic nucleus
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (2)
View details for DOI 10.1093/pasj/psx147
View details for Web of Science ID 000432287600005
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Measurements of resonant scattering in the Perseus Cluster core with Hitomi SXS
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (2)
View details for DOI 10.1093/pasj/psx127
View details for Web of Science ID 000432287600002
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Search for thermal X-ray features from the Crab nebula with the Hitomi soft X-ray spectrometer
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (2)
View details for DOI 10.1093/pasj/psx072
View details for Web of Science ID 000432287600006
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Atomic data and spectral modeling constraints from high-resolution X-ray observations of the Perseus cluster with Hitomi
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (2)
View details for DOI 10.1093/pasj/psx156
View details for Web of Science ID 000432287600004
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Glimpse of the highly obscured HMXB IGR J16318-4848 with Hitomi
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (2)
View details for DOI 10.1093/pasj/psx154
View details for Web of Science ID 000432287600009
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Atmospheric gas dynamics in the Perseus cluster observed with Hitomi
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (2)
View details for DOI 10.1093/pasj/psx138
View details for Web of Science ID 000432287600001
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Hitomi X-ray studies of giant radio pulses from the Crab pulsar
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
2018; 70 (2)
View details for DOI 10.1093/pasj/psx083
View details for Web of Science ID 000432287600007
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On the illumination of neutron star accretion discs
Monthly Notices of the Royal Astronomical Society
2018; 475 (1): 748-756
View details for DOI 10.1093/mnras/stx3167
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The Athena WFI Science Products Module
SPIE-INT SOC OPTICAL ENGINEERING. 2018
View details for DOI 10.1117/12.2312785
View details for Web of Science ID 000452819200036
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Solar abundance ratios of the iron-peak elements in the Perseus cluster
NATURE
2017; 551 (7681): 478-+
Abstract
The metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae. Therefore, X-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. In particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type Ia supernovae evolve and explode. Recent X-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the Sun, suggesting differences between the nature of type Ia supernovae in the clusters and in the Milky Way. However, because the K-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, high-resolution spectroscopy is required for an accurate determination of the abundances of these elements. Here we report observations of the Perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. Our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. Comparison between our results and modern nucleosynthesis calculations disfavours the hypothesis that type Ia supernova progenitors are exclusively white dwarfs with masses well below the Chandrasekhar limit (about 1.4 times the mass of the Sun). The observed abundance pattern of the iron-peak elements can be explained by taking into account a combination of near- and sub-Chandrasekhar-mass type Ia supernova systems, adding to the mounting evidence that both progenitor types make a substantial contribution to cosmic chemical enrichment.
View details for DOI 10.1038/nature24301
View details for Web of Science ID 000416043700039
View details for PubMedID 29132142
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The high-Eddington NLS1 Ark 564 has the coolest corona
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2017; 468 (3): 3489-3498
View details for DOI 10.1093/mnras/stx792
View details for Web of Science ID 000402808700078
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The response of relativistic outflowing gas to the inner accretion disk of a black hole
NATURE
2017; 543 (7643): 83-?
Abstract
The brightness of an active galactic nucleus is set by the gas falling onto it from the galaxy, and the gas infall rate is regulated by the brightness of the active galactic nucleus; this feedback loop is the process by which supermassive black holes in the centres of galaxies may moderate the growth of their hosts. Gas outflows (in the form of disk winds) release huge quantities of energy into the interstellar medium, potentially clearing the surrounding gas. The most extreme (in terms of speed and energy) of these-the ultrafast outflows-are the subset of X-ray-detected outflows with velocities higher than 10,000 kilometres per second, believed to originate in relativistic (that is, near the speed of light) disk winds a few hundred gravitational radii from the black hole. The absorption features produced by these outflows are variable, but no clear link has been found between the behaviour of the X-ray continuum and the velocity or optical depth of the outflows, owing to the long timescales of quasar variability. Here we report the observation of multiple absorption lines from an extreme ultrafast gas flow in the X-ray spectrum of the active galactic nucleus IRAS 13224-3809, at 0.236 ± 0.006 times the speed of light (71,000 kilometres per second), where the absorption is strongly anti-correlated with the emission of X-rays from the inner regions of the accretion disk. If the gas flow is identified as a genuine outflow then it is in the fastest five per cent of such winds, and its variability is hundreds of times faster than in other variable winds, allowing us to observe in hours what would take months in a quasar. We find X-ray spectral signatures of the wind simultaneously in both low- and high-energy detectors, suggesting a single ionized outflow, linking the low- and high-energy absorption lines. That this disk wind is responding to the emission from the inner accretion disk demonstrates a connection between accretion processes occurring on very different scales: the X-ray emission from within a few gravitational radii of the black hole ionizing the disk wind hundreds of gravitational radii further away as the X-ray flux rises.
View details for DOI 10.1038/nature21385
View details for Web of Science ID 000395671500036
View details for PubMedID 28252065
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Future of X-ray reverberation from AGN
ASTRONOMISCHE NACHRICHTEN
2017; 338 (2-3): 269-273
View details for DOI 10.1002/asna.201713341
View details for Web of Science ID 000400339900022
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Hitomi Constraints on the 3.5 keV Line in the Perseus Galaxy Cluster
ASTROPHYSICAL JOURNAL LETTERS
2017; 837 (1)
View details for DOI 10.3847/2041-8213/aa61fa
View details for Web of Science ID 000396122600001
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Revealing structure and evolution within the corona of the Seyfert galaxy I Zw 1
Monthly Notices of the Royal Astronomical Society
2017; 471 (4): 4436-4451
View details for DOI 10.1093/mnras/stx1814
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The Extremes of AGN Variability
CAMBRIDGE UNIV PRESS. 2017: 168-171
View details for DOI 10.1017/S1743921317001648
View details for Web of Science ID 000456300300038
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Probing the geometry and motion of AGN coronae through accretion disc emissivity profiles
Monthly Notices of the Royal Astronomical Society
2017; 472 (2): 1932-1945
View details for DOI 10.1093/mnras/stx2080
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The quiescent intracluster medium in the core of the Perseus cluster
NATURE
2016; 535 (7610): 117-?
Abstract
Clusters of galaxies are the most massive gravitationally bound objects in the Universe and are still forming. They are thus important probes of cosmological parameters and many astrophysical processes. However, knowledge of the dynamics of the pervasive hot gas, the mass of which is much larger than the combined mass of all the stars in the cluster, is lacking. Such knowledge would enable insights into the injection of mechanical energy by the central supermassive black hole and the use of hydrostatic equilibrium for determining cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50-million-kelvin diffuse hot plasma filling its gravitational potential well. The active galactic nucleus of the central galaxy NGC 1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These bubbles probably induce motions in the intracluster medium and heat the inner gas, preventing runaway radiative cooling--a process known as active galactic nucleus feedback. Here we report X-ray observations of the core of the Perseus cluster, which reveal a remarkably quiescent atmosphere in which the gas has a line-of-sight velocity dispersion of 164 ± 10 kilometres per second in the region 30-60 kiloparsecs from the central nucleus. A gradient in the line-of-sight velocity of 150 ± 70 kilometres per second is found across the 60-kiloparsec image of the cluster core. Turbulent pressure support in the gas is four per cent of the thermodynamic pressure, with large-scale shear at most doubling this estimate. We infer that a total cluster mass determined from hydrostatic equilibrium in a central region would require little correction for turbulent pressure.
View details for DOI 10.1038/nature18627
View details for Web of Science ID 000379015600035
View details for PubMedID 27383985
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Towards modelling X-ray reverberation in AGN: piecing together the extended corona
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2016; 458 (1): 200-225
View details for DOI 10.1093/mnras/stw276
View details for Web of Science ID 000374568900011
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Driving extreme variability: Measuring the evolving coronae and evidence for jet launching in AGN
ASTRONOMISCHE NACHRICHTEN
2016; 337 (4-5): 557-562
View details for DOI 10.1002/asna.201612347
View details for Web of Science ID 000375725600037
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The ASTRO-H (Hitomi) X-ray Astronomy Satellite
SPIE-INT SOC OPTICAL ENGINEERING. 2016
View details for DOI 10.1117/12.2232379
View details for Web of Science ID 000387731500019
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Flaring from the supermassive black hole in Mrk 335 studied with Swift and NuSTAR
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2015; 454 (4): 4440-4451
View details for DOI 10.1093/mnras/stv2130
View details for Web of Science ID 000368001600085
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Driving extreme variability: the evolving corona and evidence for jet launching in Markarian 335
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2015; 449 (1): 129-146
View details for DOI 10.1093/mnras/stv162
View details for Web of Science ID 000355345600012
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The Comptonization of accretion disc X-ray emission: consequences for X-ray reflection and the geometry of AGN coronae
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2015; 448 (1): 703-712
View details for DOI 10.1093/mnras/stu2524
View details for Web of Science ID 000350273500048
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NEW CONSTRAINTS ON THE BLACK HOLE LOW/HARD STATE INNER ACCRETION FLOW WITH NuSTAR
ASTROPHYSICAL JOURNAL LETTERS
2015; 799 (1)
View details for DOI 10.1088/2041-8205/799/1/L6
View details for Web of Science ID 000348143500006
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Suzaku observations of Mrk 335: confronting partial covering and relativistic reflection
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2015; 446 (1): 633-650
View details for DOI 10.1093/mnras/stu2108
View details for Web of Science ID 000347518300045
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Modelling the extreme X-ray spectrum of IRAS 13224-3809
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2015; 446 (1): 759-769
View details for DOI 10.1093/mnras/stu2087
View details for Web of Science ID 000347518300055
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Caught in the act: measuring the changes in the corona that cause the extreme variability of 1H 0707-495
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2014; 443 (3): 2746-2756
View details for DOI 10.1093/mnras/stu1273
View details for Web of Science ID 000342920400064
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The NuSTAR spectrum of Mrk 335: extreme relativistic effects within two gravitational radii of the event horizon?
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2014; 443 (2): 1723-1732
View details for DOI 10.1093/mnras/stu1246
View details for Web of Science ID 000340436800062
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X-ray reverberation around accreting black holes
ASTRONOMY AND ASTROPHYSICS REVIEW
2014; 22
View details for DOI 10.1007/s00159-014-0072-0
View details for Web of Science ID 000344432400001
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On the determination of the spin and disc truncation of accreting black holes using X-ray reflection
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2014; 439 (3): 2307-2313
View details for DOI 10.1093/mnras/stu045
View details for Web of Science ID 000334114900006
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Modelling the broad Fe K alpha reverberation in the AGN NGC 4151
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2014; 438 (4): 2980-2994
View details for DOI 10.1093/mnras/stt2424
View details for Web of Science ID 000332038000020
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The ASTRO-H X-ray Astronomy Satellite
SPIE-INT SOC OPTICAL ENGINEERING. 2014
View details for DOI 10.1117/12.2055681
View details for Web of Science ID 000354529100065
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Discovery of high-frequency iron K lags in Ark 564 and Mrk 335
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2013; 434 (2): 1129-1137
View details for DOI 10.1093/mnras/stt1055
View details for Web of Science ID 000323638200015
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The origin of the lag spectra observed in AGN: Reverberation and the propagation of X-ray source fluctuations
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2013; 430 (1): 247-258
View details for DOI 10.1093/mnras/sts591
View details for Web of Science ID 000318274500031
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Long XMM observation of the narrow-line Seyfert 1 galaxy IRAS 13224-3809: rapid variability, high spin and a soft lag
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2013; 429 (4): 2917-2923
View details for DOI 10.1093/mnras/sts504
View details for Web of Science ID 000318272600010
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The closest look at 1H0707-495: X-ray reverberation lags with 1.3 Ms of data
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2013; 428 (4): 2795-2804
View details for DOI 10.1093/mnras/sts155
View details for Web of Science ID 000318232000002
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Understanding X-ray reflection emissivity profiles in AGN: locating the X-ray source
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2012; 424 (2): 1284-1296
View details for DOI 10.1111/j.1365-2966.2012.21308.x
View details for Web of Science ID 000306356800037
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On the determination of the spin of the black hole in Cyg X-1 from X-ray reflection spectra
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2012; 424 (1): 217-223
View details for DOI 10.1111/j.1365-2966.2012.21185.x
View details for Web of Science ID 000306140600018
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Testing the accuracy of radiative cooling approximations in smoothed particle hydrodynamical simulations
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2012; 419 (4): 3368-3377
View details for DOI 10.1111/j.1365-2966.2011.19976.x
View details for Web of Science ID 000298920600048
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1H 0707-495 in 2011: an X-ray source within a gravitational radius of the event horizon
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2012; 419 (1): 116-123
View details for DOI 10.1111/j.1365-2966.2011.19676.x
View details for Web of Science ID 000298303300026
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Determination of the X-ray reflection emissivity profile of 1H 0707-495
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
2011; 414 (2): 1269-1277
View details for DOI 10.1111/j.1365-2966.2011.18458.x
View details for Web of Science ID 000292740500033