74 citations · 775 across the 53 of their papers we have counts for
47 papers · 1 filter
Polarization of Synchrotron Emission from Rotation Powered Pulsars
Seima Saeki, Shota Kisaka, Jumpei Takata
With the launch of the Imaging X-ray Polarimeter Explorer in 2021, recent observations have provided X-ray polarization data for several rotation-powered pulsars. To fully exploit…
VLBI Astrometry of Magnetars
Takuya Akahori, Sujin Eie, Kei Amada +8
The origin of the strongest magnetic fields in the Universe, i.e., the origin of magnetars, is a longstanding question. An enhanced dynamo effect in an irregular supernova explosio…
Constraining the Pulsar Beaming Fraction with TeV-Selected Galactic Pulsar Wind Nebulae and unidentified TeV Sources
Takumi Shimasue, Shota Kisaka, Aya Bamba +1
The pulsar beaming fraction is a fundamental quantity for connecting the observed pulsar population to the intrinsic Galactic population and for constraining pulsar emission geomet…
Gyromagnetic Angular Momentum Interconversion in Neutron Stars
Hiroshi Funaki, Yuta Sekino, Hiroyuki Tajima +3
We propose a novel mechanism for angular momentum (AM) exchange between the crust and core of a neutron star (NS) via the gyromagnetic effect. Using extended hydrodynamics, we mode…
The centrifugal acceleration and the Y-point of the Pulsar Magnetosphere
Shinpei Shibata, Shota Kisaka
We investigate the centrifugal acceleration in an axisymmetric pulsar magnetosphere under the ideal-MHD approximation. We solved the field-aligned equations of motion for flows ins…
On the X-ray efficiency of the white dwarf pulsar candidate ZTF J190132.9+145808.7
Aya Bamba, Yukikatsu Terada, Kazumi Kashiyama +3
Strongly magnetized, rapidly rotating massive white dwarfs (WDs) emerge as potential outcomes of double degenerate mergers. These WDs can act as sources of non-thermal emission and…
1D GRPIC Simulations of Stellar-Mass Black Hole Magnetospheres: Semi-Analytic Model of Gamma-Rays from Gaps
Koki Kin, Shota Kisaka, Kenji Toma +2
In the absence of a sufficient amount of plasma injection into the black hole (BH) magnetosphere, the force-free state of the magnetosphere cannot be maintained, leading to the eme…
Evolutionary deformation toward the elastic limit by a magnetic field confined in the neutron--star crust
Yasufumi Kojima, Shota Kisaka, Kotaro Fujisawa
Occasional energetic outbursts and anomalous X-ray luminosities are expected to be powered by the strong magnetic field in a neutron star. For a very strong magnetic field, elastic…
Strong toroidal magnetic fields sustained by the elastic crust in a neutron star
Kotaro Fujisawa, Yasufumi Kojima, Shota Kisaka
We investigate new solutions for magnetized neutron stars with a barotropic core in magnetohydrodynamic (MHD) equilibrium and a magneto-elastic crust, which was neglected by previo…
Detection of a bright burst from the repeating FRB 20201124A at 2 GHz
Sota Ikebe, Kazuhiro Takefuji, Toshio Terasawa +14
We present a detection of a bright burst from FRB 20201124A, which is one of the most active repeating FRBs, based on S-band observations with the 64-m radio telescope at the Usuda…
Magnetic field sustained by the elastic force in neutron star crusts
Yasufumi Kojima, Shota Kisaka, Kotaro Fujisawa
We investigate the magneto--elastic equilibrium of a neutron star crust and magnetic energy stored by the elastic force. The solenoidal motion driven by the Lorentz force can be co…
Multi-frequency radio observations of the radio-loud magnetar XTE J1810-197
Sujin Eie, Toshio Terasawa, Takuya Akahori +11
We report on the multi-frequency multi-epoch radio observations of the magnetar, XTE J1810-197, which exhibited a radio outburst from December 2018 after its 10-year quiescent peri…
A month of monitoring the new magnetar Swift J1555.2-5402 during an X-ray outburst
Teruaki Enoto, Mason Ng, Chin-ping Hu +23
The soft gamma-ray repeater Swift J1555.2-5402 was discovered by means of a 12-ms duration short burst detected with Swift BAT on 2021 June 3. Then 1.6 hours after the first burst…
The response of black hole spark gaps to external changes: A production mechanism of rapid TeV flares?
Shota Kisaka, Amir Levinson, Kenji Toma +1
We study the response of a starved Kerr black hole magnetosphere to abrupt changes in the intensity of disk emission and in the global magnetospheric current, by means of 1D genera…
On the Angular Momentum Extraction from the Rotation Powered Pulsars
Shinpei Shibata, Shota Kisaka
The rotation powered pulsar loses angular momentum at a rate of the rotation power divided by the angular velocity . This means that the length of the lever arm of the angular…
Magneto-elastic equilibrium of a neutron-star crust
Yasufumi Kojima, Shota Kisaka, Kotaro Fujisawa
We examine the equilibrium of a magnetized neutron-star-crust. We calculate axially symmetric models in which an elastic force balances solenoidal motion driven by a Lorentz force.…
Enhanced X-ray Emission Coinciding with Giant Radio Pulses from the Crab Pulsar
Teruaki Enoto, Toshio Terasawa, Shota Kisaka +34
Giant radio pulses (GRPs) are sporadic bursts emitted by some pulsars, lasting a few microseconds. GRPs are hundreds to thousands of times brighter than regular pulses from these s…
Evolution of magnetic deformation in neutron star crust
Yasufumi Kojima, Shota Kisaka, Kotaro Fujisawa
In this study, we examine the magnetic field evolution occurring in a neutron star crust. Beyond the elastic limit, the lattice ions are assumed to act as a plastic flow. The Ohmic…
Comprehensive analysis of magnetospheric gaps around Kerr black holes using 1D GRPIC simulations
Shota Kisaka, Amir Levinson, Kenji Toma
Spark gaps are likely the source of plasma in active black hole (BH) magnetospheres. In this paper, we present results of 1D general-relativistic particle-in-cell simulations of a…
Suzaku and Fermi view of the supernova remnant 3C 396
Aytap Sezer, Tulun Ergin, Nergis Cesur +4
3C 396 is a composite supernova remnant (SNR), consisting of a central pulsar wind nebula (PWN) and a bright shell in the west, which is known to be interacting with molecular clou…
Upscattered Cocoon Emission in Short Gamma-ray Bursts as High-energy Gamma-ray Counterparts to Gravitational Waves
Shigeo S. Kimura, Kohta Murase, Kunihito Ioka +3
We investigate prolonged engine activities of short gamma-ray bursts (SGRBs), such as extended and/or plateau emissions, as high-energy gamma-ray counterparts to gravitational wave…
Exponentially Decaying Extended Emissions Following Short Gamma-Ray Bursts with Possible Luminosity -- E-folding Time Correlation
Yasuaki Kagawa, Daisuke Yonetoku, Tatsuya Sawano +3
The origin of extended emissions following prompt emissions of short gamma-ray bursts (SGRBs) is in mystery. The long-term activity of the extended emission is responsible for prom…
Relativistic Fireball Reprise: Radio Suppression at the Onset of Short Magnetar Bursts
Shotaro Yamasaki, Shota Kisaka, Toshio Terasawa +1
There is growing evidence that a clear distinction between magnetars and radio pulsars may not exist, implying the population of neutron stars that exhibit both radio pulsations an…
Is the macronova in GW170817 powered by the central engine?
Tatsuya Matsumoto, Kunihito Ioka, Shota Kisaka +1
The gravitational wave event GW170817 from a binary neutron star (NS) merger is accompanied by electromagnetic counterparts, and the optical and near-infared emission is called a m…