Article
Astronomy & Astrophysics
J. N. Reeves, V Braito, D. Porquet, A. P. Lobban, G. A. Matzeu, E. Nardini
Summary: New Swift monitoring observations of the variable, radio-quiet quasar, PDS 456, show a bright X-ray flare captured in September 2018, with a flux increase of 4 times. The coronal size is inferred to be less than or equal to 30 gravitational radii according to the light crossing argument, with a total flare energy exceeding 10^51 erg. The X-ray flare is produced in the X-ray corona and is accompanied by a hardening of the X-ray emission.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
L. Haerer, M. L. Parker, A. Joyce, Z. Igo, W. N. Alston, F. Furst, A. P. Lobban, G. A. Matzeu, J. N. Reeves
Summary: An improved model is presented to describe excess variance spectra of ultrafast outflows in the quasar Pico del Dias Survey (PDS) 456. The model successfully explains the broadening of spike-like features in the outflows and suggests structured outflows with multiple layers of different velocities in PDS 456.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
D. J. Walton, M. Balokovic, A. C. Fabian, L. C. Gallo, M. Koss, E. Nardini, C. S. Reynolds, C. Ricci, D. Stern, W. N. Alston, T. Dauser, J. A. Garcia, P. Kosec, M. T. Reynolds, F. A. Harrison, J. M. Miller
Summary: The study presents a high signal-to-noise broad-band X-ray spectrum of the Seyfert galaxy ESO033-G002, revealing complex features such as neutral and ionized absorption, as well as disc reflection. The research also estimates the mass of the black hole in the galaxy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
M. Sobolenko, O. Kompaniiets, P. Berczik, V Marchenko, A. Vasylenko, E. Fedorova, B. Shukirgaliyev
Summary: This research estimates the physical coalescence time of the double supermassive black hole system in NGC 6240 based on X-ray observations, with a calculated upper limit for merging time around 70 Myr using numerical models and spectroscopic data.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
James K. Williams, Mario Gliozzi, Kyle A. Bockwoldt, Onic Shuvo
Summary: Accurately determining black hole mass (M-BH) is crucial for studying the properties and evolution of active galactic nuclei (AGNs). While direct methods can be used for unobscured type 1 AGNs, only indirect methods can be applied to heavily absorbed type 2 AGNs. This study assessed the reliability of three indirect methods using the Seyfert galaxy NGC 4151 and found that the X-ray scaling method and the M-sigma correlation are both accurate and precise in estimating M-BH for obscured AGNs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Andrew King, Rebecca Nealon
Summary: Recent research has found that the sample size of dwarf galaxies with measured central black hole masses and velocity dispersions has doubled, showing a close fit to the extrapolation of the M-sigma relation for more massive galaxies. This challenges the idea that the scaling relations between galaxies and their central black holes are merely a statistical consequence of assembly through repeated mergers. The prediction of significantly larger black hole masses in dwarf galaxies suggests an initial distribution of uncorrelated seed black hole and stellar masses confined to much smaller masses than previously assumed.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Jun Yang, Zsolt Paragi, Emanuele Nardini, Willem A. Baan, Lulu Fan, Prashanth Mohan, Eskil Varenius, Tao An
Summary: PDS 456, with its massive black hole and energetic X-ray winds, exhibits significant radio activity possibly originated from complex jets or high-speed winds impacting on star-forming regions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Ryota Tomaru, Chris Done, Junjie Mao
Summary: Black hole accretion discs can produce powerful outflowing plasma known as disc winds, which play a crucial role in controlling galaxy formation. The launch mechanism of these winds is still a topic of debate. Previous studies argued that magnetic driving was the only viable mechanism based on an observation of a stellar-mass black hole. However, our reanalysis of the data using a photoionization code suggests that a thermal-radiative wind model matches better with the data. These results challenge the basis of the unified magnetic wind models extrapolated to quasar outflows.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
S. Komossa, D. Grupe, M. L. Parker, J. L. Gomez, M. J. Valtonen, M. A. Nowak, S. G. Jorstad, D. Haggard, S. Chandra, S. Ciprini, L. Dey, A. Gopakumar, K. Hada, S. Markoff, J. Neilsen
Summary: The study conducted a comprehensive analysis of the X-ray and ultraviolet spectra of the bright blazar OJ 287, revealing highly variable spectra with three spectral components. Observations over a period of 15 years showed that OJ 287 experienced extreme minima and outburst states.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Alessia Tortosa, Claudio Ricci, Patricia Arevalo, Michael J. Koss, Franz E. Bauer, Benny Trakhtenbrot, Richard Mushotzky, Matthew J. Temple, Federica Ricci, Alejandra Rojas Lilayu, Taiki Kawamuro, Turgay Caglar, Tingting Liu, Fiona Harrison, Kyuseok Oh, Meredith Clark Powell, Daniel Stern, Claudia Megan Urry
Summary: We investigate the X-ray variability properties of Seyfert 1 Galaxies belonging to the BAT AGN Spectroscopic Survey (BASS). We find a significant correlation between normalized excess variance and black hole masses, as well as a correlation with AGN luminosities. We also explore the differences in variability between different energy bands.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
P. Chainakun, I Fongkaew, S. Hancock, A. J. Young
Summary: Neural network models are developed in this study for predicting the black hole mass, and the accuracy of the predictions is found to be significantly higher compared to traditional linear regression methods. This suggests that neural network techniques are a promising and independent way to estimate the black hole mass. The study also investigates the global relations when the number of reverberating AGNs increases through simulations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Emily Moravec, Jiri Svoboda, Abhijeet Borkar, Peter Boorman, Daniel Kynoch, Francesca Panessa, Beatriz Mingo, Matteo Guainazzi
Summary: This study investigates the observational features of accreting supermassive black holes and stellar mass black holes, explores the similarities between AGNs and XRBs in terms of spectral states, and classifies radio AGNs. The results show that different categories of AGNs occupy distinct regions in the HID, demonstrating similarities to XRBs.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Mario Gliozzi, James K. Williams, Dina A. Michel
Summary: In this study, the validity of an X-ray-based scaling method to constrain black hole masses in heavily obscured AGN was tested. The results showed that fitting X-ray broad-band spectra with physically motivated self-consistent models could yield MBH values consistent with those determined from other measurements.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Physics, Multidisciplinary
Ye Feng, XueShan Zhao, LiJun Gou, YuFeng Li, James F. Steiner, Javier A. Garcia, Yuan Wang, Nan Jia, ZhenXuan Liao, HuiXian Li
Summary: AT2019wey is a new galactic X-ray binary consisting of a black hole candidate and a low-mass companion star. It exhibits a low/hard state during its X-ray outburst, with a high spin and inner disk inclination angle, as well as a relatively high iron abundance and disk ionization state.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2022)
Article
Astronomy & Astrophysics
John A. Regan, Fabio Pacucci, M. J. Bustamante-Rosell
Summary: Observational evidence suggests that there is a continuum in the mass spectrum of massive black holes (MBHs) in dwarf galaxies, which could be a unique signature of a heavy seed formation pathway. This continuum consists of stellar mass black holes formed through stellar evolution, as well as a smaller population of heavy seed MBHs that have not yet sunk to the center of the galaxy. The detection of off-centred MBHs and a central MBH would provide strong evidence of a heavy seeding pathway.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Tenyo Kawamura, Magnus Axelsson, Chris Done, Tadayuki Takahashi
Summary: The nature and geometry of the accretion flow in the low/hard state of black hole binaries is currently controversial. In this study, a full spectral-timing analysis was performed on a bright low/hard state of MAXI J1820+070 using NICER and NuSTAR data, combining spectral fitting and additional information from fast X-ray variability. The results suggest a model with propagating mass accretion rate fluctuations, which successfully explains the observed double-humped shape of the power spectra and the increasing high-frequency variability with energy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Multidisciplinary Sciences
S. Scaringi, P. J. Groot, C. Knigge, A. J. Bird, E. Breedt, D. A. H. Buckley, Y. Cavecchi, N. D. Degenaar, D. de Martino, C. Done, M. Fratta, K. Itkiewicz, E. Koerding, J-P Lasota, C. Littlefield, C. F. Manara, M. O'Brien, P. Szkody, F. X. Timmes
Summary: Unexplained rapid bursts have been observed from TV Columbae and other accreting systems, resembling classical nova explosions and type-I X-ray bursts.
Article
Multidisciplinary Sciences
I-Huan Chiu, Shin'ichiro Takeda, Meito Kajino, Atsushi Shinohara, Miho Katsuragawa, Shunsaku Nagasawa, Ryota Tomaru, Goro Yabu, Tadayuki Takahashi, Shin Watanabe, Soshi Takeshita, Yasuhiro Miyake, Kazuhiko Ninomiya
Summary: Elemental analysis based on muonic X-rays offers a non-destructive way to obtain information about material composition, which is particularly valuable for precious or unreachable samples. In this study, a novel 3D elemental analysis technique was developed by combining the analysis method using negative muons with a cadmium telluride double-sided strip detector. The technique was successfully applied to analyze the 3D distribution of carbon in bulk samples and the stopping depth of muons.
SCIENTIFIC REPORTS
(2022)
Article
Engineering, Biomedical
Atsushi Yagishita, Shin'ichiro Takeda, Miho Katsuragawa, Tenyo Kawamura, Hideaki Matsumura, Tadashi Orita, Izumi O. Umeda, Goro Yabu, Pietro Caradonna, Tadayuki Takahashi, Shin Watanabe, Yousuke Kanayama, Hiroshi Mizuma, Kazunobu Ohnuki, Hirofumi Fujii
Summary: This study reports the development and performance of an imaging system equipped with a cadmium telluride diode detector that achieves high energy and spatial resolutions. By fitting high-resolution spectra to an X-ray analysis model, multiple radionuclides can be simultaneously visualized in living tissue.
NATURE BIOMEDICAL ENGINEERING
(2022)
Article
Radiology, Nuclear Medicine & Medical Imaging
Goro Yabu, Hiroki Yoneda, Tadashi Orita, Shin'ichiro Takeda, Pietro Caradonna, Tadayuki Takahashi, Shin Watanabe, Fumiki Moriyama
Summary: This study used a Si/CdTe Compton camera with high angular and high energy resolutions to perform short-distance imaging experiments. By using phantom composed of In-111 and I-131 solutions, the positions of sources were successfully reproduced. The results showed that the list-mode maximum-likelihood expectation maximization method provided better resolution. These findings suggest the potential of Compton Cameras for close-distance imaging of radioisotope distributions below 400 keV.
IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES
(2022)
Article
Astronomy & Astrophysics
Juan Camilo Buitrago-Casas, Lindsay Glesener, Steven Christe, Sam Krucker, Juliana Vievering, P. S. Athiray, Sophie Musset, Lance Davis, Sasha Courtade, Gregory Dalton, Paul Turin, Zoe Turin, Brian Ramsey, Stephen Bongiorno, Daniel Ryan, Tadayuki Takahashi, Kento Furukawa, Shin Watanabe, Noriyuki Narukage, Shin-nosuke Ishikawa, Ikuyuki Mitsuishi, Kouichi Hagino, Van Shourt, Jessie Duncan, Yixian Zhang, Stuart D. Bale
Summary: This study presents constraints on the quiet-Sun HXR emission in the 5-10 keV range using FOXSI-2 and -3 observations. It reports upper limits for the HXR emission and compares the results with those obtained from RHESSI observations. FOXSI achieved similar results with significantly less observation time compared to RHESSI.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Shunsaku Nagasawa, Tomoko Kawate, Noriyuki Narukage, Tadayuki Takahashi, Amir Caspi, Thomas N. Woods
Summary: In this study, we conducted a wide-band X-ray spectral analysis to examine the time evolution of an M7.6-class flare using the MinXSS and RHESSI instruments. We found that the emission measures of the cool and hot thermal components drastically increased, while the superhot thermal component gradually appeared after the peak of nonthermal emission. Additionally, the analysis of the differential emission measure revealed an increase in the emission of cool plasma.
ASTROPHYSICAL JOURNAL
(2022)
Article
Instruments & Instrumentation
T. Fukuchi, S. Takeda, M. Katsuragawa, G. Yabu, S. Watanabe, T. Takahashi, Y. Watanabe
Summary: We developed a gamma-ray computed tomography system using a CdTe double-sided strip detector. The system provides highly accurate images due to its fine strip pitch and high energy resolution with photon-counting capability. The system's performance was evaluated through transmission measurements for various materials, and the results agreed well with simulations. The system successfully reconstructed the three-dimensional structure of a rod-phantom and distinguished the elements inside.
JOURNAL OF INSTRUMENTATION
(2023)
Article
Astronomy & Astrophysics
Ryota Tomaru, Chris Done, Junjie Mao
Summary: Black hole accretion discs can produce powerful outflowing plasma known as disc winds, which play a crucial role in controlling galaxy formation. The launch mechanism of these winds is still a topic of debate. Previous studies argued that magnetic driving was the only viable mechanism based on an observation of a stellar-mass black hole. However, our reanalysis of the data using a photoionization code suggests that a thermal-radiative wind model matches better with the data. These results challenge the basis of the unified magnetic wind models extrapolated to quasar outflows.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Tenyo Kawamura, Chris Done, Magnus Axelsson, Tadayuki Takahashi
Summary: Black hole X-ray binaries exhibit stochastic variability on short time scales, with complex lags in correlated variability observed across different energy bands. This is usually explained by a model where slow fluctuations originating at large radii propagate through the accretion flow, modulating faster fluctuations generated at smaller radii. By incorporating radially stratified emission, it becomes possible to measure the propagation time scale from data, enabling direct tests of the accretion flow structure. However, when applying a previously developed model to higher energy variability data from the Insight-Hard X-ray Modulation Telescope (HXMT), it fails to accurately fit the observed behavior.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Review
Astronomy & Astrophysics
P. Gandhi, T. Kawamuro, M. Diaz Trigo, J. A. Paice, P. G. Boorman, M. Cappi, C. Done, A. C. Fabian, K. Fukumura, J. A. Garcia, C. L. Greenwell, M. Guainazzi, K. Makishima, M. S. Tashiro, R. Tomaru, F. Tombesi, Y. Ueda
Summary: Microcalorimeters have been successful in studying the hot and energetic Universe, and have provided answers to important questions in compact-object science. Improvements in laboratory data and plasma modeling can further enhance the performance of microcalorimeters.
Article
Astronomy & Astrophysics
Ryota Tomaru, Done Chris, Hirokazu Odaka, Atsushi Tanimoto
Summary: Accretion disc coronae (ADC) sources are high inclination neutron star or black hole binaries, where the central source is obscured by the outer accretion flow. The observed X-ray emission is mainly produced by scattering of radiation from highly ionized gas surrounding the source. The origin of this scattering material is still debated. In this study, we used the ADC source 2S 0921-630 (V395 Car) to test whether a thermal-radiative wind produced by the central X-ray source can explain the observed emission. We found that our model agrees with the emission lines observed in the wind, supporting thermal-radiative winds as the origin of the ADC.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Physics, Multidisciplinary
Nobuyuki Nakamura, Naoki Numadate, Simpei Oishi, Xiao-Min Tong, Xiang Gao, Daiji Kato, Hirokazu Odaka, Tadayuki Takahashi, Yutaka Tsuzuki, Yuusuke Uchida, Hirofumi Watanabe, Shin Watanabe, Hiroki Yoneda
Summary: We demonstrate that the 1s22s22p1/2 - 1s2s22p21/2 transition in Pb77+ emitted during the dielectronic recombination of Pb78+ exhibits strong polarization, despite being an intrinsically unpolarized J = 1/2 to 1/2 transition. This unexpected polarization is attributed to quantum interference with radiative recombination. The interference effect, previously studied on an asymmetric resonance profile, is shown to have a significant impact on polarization even for a nearly symmetric resonance, suggesting a small interference.
PHYSICAL REVIEW LETTERS
(2023)
Article
Optics
Naoki Numadate, Shimpei Oishi, Hirokazu Odaka, Priti, Makoto Sakurai, Tadayuki Takahashi, Yutaka Tsuzuki, Yuusuke Uchida, Hirofumi Watanabe, Shin Watanabe, Hiroki Yoneda, Nobuyuki Nakamura
Summary: This study reports a polarization measurement of L-shell radiative recombination x rays emitted from bismuth ions with different charge states. The observed degree of linear polarization is 0.666, while the theoretical estimation yields a value of 0.716. The discrepancy between the observed and theoretical values is likely due to electron correlation effects.