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50 papers
Follow-up Observations for IceCube-170922A: Detection of Rapid Near-Infrared Variability and Intensive Monitoring of TXS 0506+056
Tomoki Morokuma, Yousuke Utsumi, Kouji Ohta +35
We present our follow-up observations to search for an electromagnetic counterpart of the IceCube high-energy neutrino, IceCube-170922A. Monitoring observations of a likely counter…
Blazar Radio and Optical Survey (BROS): A catalog of blazar candidates showing flat radio spectrum and their optical identification in Pan-STARRS1 Surveys
Ryosuke Itoh, Yousuke Utsumi, Yoshiyuki Inoue +5
Utilizing the latest and the most sensitive radio and optical catalogs, we completed a new blazar candidate catalog, Blazar Radio and Optical Survey (BROS), which includes 88,211 s…
Detection of polarized gamma-ray emission from the Crab nebula with Hitomi Soft Gamma-ray Detector
Hitomi Collaboration, Felix Aharonian, Hiroki Akamatsu +191
We present the results from the Hitomi Soft Gamma-ray Detector (SGD) observation of the Crab nebula. The main part of SGD is a Compton camera, which in addition to being a spectrom…
Multi-messenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A
The IceCube, Fermi-LAT, MAGIC +13
Individual astrophysical sources previously detected in neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neut…
Modeling of proton-induced radioactivation background in hard X-ray telescopes: Geant4-based simulation and its demonstration by Hitomi's measurement in a low Earth orbit
Hirokazu Odaka, Makoto Asai, Kouichi Hagino +47
Hard X-ray astronomical observatories in orbit suffer from a significant amount of background due to radioactivation induced by cosmic-ray protons and/or geomagnetically trapped pr…
Temperature Structure in the Perseus Cluster Core Observed with Hitomi
Hitomi Collaboration, Felix Aharonian, Hiroki Akamatsu +192
The present paper investigates the temperature structure of the X-ray emitting plasma in the core of the Perseus cluster using the 1.8--20.0 keV data obtained with the Soft X-ray S…
Hitomi Observation of Radio Galaxy NGC 1275: The First X-ray Microcalorimeter Spectroscopy of Fe-Kα Line Emission from an Active Galactic Nucleus
Hitomi Collaboration, Felix Aharonian, Hiroki Akamatsu +191
The origin of the narrow Fe-Kα fluorescence line at 6.4 keV from active galactic nuclei has long been under debate; some of the possible sites are the outer accretion disk, the bro…
Atmospheric gas dynamics in the Perseus cluster observed with Hitomi
Hitomi Collaboration, Felix Aharonian, Hiroki Akamatsu +195
Extending the earlier measurements reported in Hitomi collaboration (2016, Nature, 535, 117), we examine the atmospheric gas motions within the central 100~kpc of the Perseus clust…
Hitomi X-ray studies of Giant Radio Pulses from the Crab pulsar
Hitomi Collaboration, Felix Aharonian, Hiroki Akamatsu +201
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 satel…
OISTER Optical and Near-Infrared Monitoring Observations of a Peculiar Radio-Loud Active Galactic Nucleus SDSS J110006.07+442144.3
Tomoki Morokuma, Masaomi Tanaka, Yasuyuki T. Tanaka +80
We present monitoring campaign observations at optical and near-infrared (NIR) wavelengths for a radio-loud active galactic nucleus (AGN) at z=0.840, SDSS~J110006.07+442144.3 (here…
Search for Thermal X-ray Features from the Crab nebula with Hitomi Soft X-ray Spectrometer
Hitomi Collaboration, Felix Aharonian, Hiroki Akamatsu +192
The Crab nebula originated from a core-collapse supernova (SN) explosion observed in 1054 A.D. When viewed as a supernova remnant (SNR), it has an anomalously low observed ejecta m…
Disk-Jet Connection in Active Supermassive Black Holes in the Standard Accretion Disk Regime
Yoshiyuki Inoue, Akihiro Doi, Yasuyuki T. Tanaka +2
We study the disk-jet connection in supermassive black holes by investigating the properties of their optical and radio emissions utilizing the SDSS-DR7 and the NVSS catalogs. Our…
High Energy Gamma Rays from Nebulae Associated with Extragalactic Microquasars and Ultra-Luminous X-ray Sources
Yoshiyuki Inoue, Shiu-Hang Lee, Yasuyuki T. Tanaka +1
In the extragalactic sky, microquasars and ultra-luminous X-ray sources (ULXs) are known as energetic compact objects locating at off-nucleus positions in galaxies. Some of these o…
Measurement of Interstellar Polarization and Estimation of Galactic Extinction for the Direction of X-ray Black Hole Binary V404 Cygni
Ryosuke Itoh, Yasuyuki T. Tanaka, Koji S. Kawabata +12
V404 Cygni is a well-known black hole binary candidate thought to have relativistic jets. It showed extreme outbursts on June 2015, characterized by a large amplitude and short tim…
Systematic Study of Gamma-ray bright Blazars with Optical Polarization and Gamma-ray Variability
Ryosuke Itoh, Krzysztof Nalewajko, Yasushi Fukazawa +18
Blazars are highly variable active galactic nuclei which emit radiation at all wavelengths from radio to gamma-rays. Polarized radiation from blazars is one key piece of evidence f…
X-ray variability of GeV gamma-ray emitting radio galaxy NGC 1275
Yasushi Fukazawa, Kensei Shiki, Yasuyuki Tanaka +2
We analyzed Suzaku/XIS data of 2006--2015 observations of a gamma-ray emitting radio galaxy NGC 1275, and brightening of the nucleus in the X-ray band was found in 2013--2015, corr…
The Quiescent Intracluster Medium in the Core of the Perseus Cluster
Hitomi Collaboration, Felix Aharonian, Hiroki Akamatsu +213
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 a host…
Hitomi constraints on the 3.5 keV line in the Perseus galaxy cluster
Hitomi Collaboration, Felix A. Aharonian, Hiroki Akamatsu +215
High-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E=3.5 keV emission line reported in several low-resolution studies of va…
EVN Observations of HESS J1943+213: Evidence for an Extreme TeV BL Lac Object
Kazunori Akiyama, Łukasz Stawarz, Yasuyuki T. Tanaka +3
We report on the 1.6 GHz (18 cm) VLBI observations of the unresolved, steady TeV source HESS J1943+213 located in the Galactic plane, performed with the European VLBI Network (EVN)…
A significant hardening and rising shape detected in the MeV/GeV nuFnu spectrum from the recently-discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 February
Y. T. Tanaka, J. Becerra Gonzalez, R. Itoh +18
We report on Fermi Large Area Telescope (LAT) and multi-wavelength results on the recently-discovered very-high-energy (VHE, 100 GeV) blazar S4 0954+65 () during an e…
Baryon Loading Efficiency and Particle Acceleration Efficiency of Relativistic Jets: Cases For Low Luminosity BL Lacs
Yoshiyuki Inoue, Yasuyuki T. Tanaka
Relativistic jets launched by supermassive black holes, so-called as active galactic nuclei (AGNs), are known as the most energetic particle accelerators in the universe. However,…
Binary Black Hole Merger Rates Inferred from Luminosity Function of Ultra-Luminous X-ray Sources
Yoshiyuki Inoue, Yasuyuki T. Tanaka, Naoki Isobe
The Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) has detected direct signals of gravitational waves (GWs) from GW150914. The event was a merger of binary bl…
Lower Bound on the Cosmic TeV Gamma-ray Background Radiation
Yoshiyuki Inoue, Yasuyuki T. Tanaka
The Fermi gamma-ray space telescope has revolutionized our understanding of the cosmic gamma-ray background radiation in the GeV band. However, investigation on the cosmic TeV gamm…
No Evidence of Intrinsic Optical/Near-Infrared Linear Polarization for V404 Cygni During its Bright Outburst in 2015: Broadband Modeling and Constraint on Jet Parameters
Y. T. Tanaka, R. Itoh, M. Uemura +39
We present simultaneous optical and near-infrared (NIR) polarimetric results for the black hole binary V404 Cygni spanning the duration of its 7-day long optically-brightest phase…