We explore physics behind hot, energetic phenomena in the universe through a wide variety of telescopes including space-based X-ray observatories. Our research particularly focuses on high energy physical processes associated with supernova remnants, neutron stars, and black holes. We also develop new observational instruments for future satellite missions.



Asymmetric Expansion of the Fe ejecta in Kepler’s Supernova Remnant

Our paper titled “Asymmetric Expansion of the Fe ejecta in Kepler’s Supernova Remnant” has been accepted for publication in PASJ. arXiv: https://arxiv.org/abs/1807.04029 The ejecta kinematics of supernova remnants (SNRs) is one of crucial clues to understand the explosion mechanism of type Ia supernovae (SNe). In particular, the kinematic asymmetry of iron-peak elements provides the key to understanding physical processes taking place in the core of the exploding white dwarfs (WDs) although it has been poorly understood by observations. Kasuga et al. shows for the first time the asymmetric expansion structure in the line-of-sight direction of Fe ejecta in Kepler’s SNR …

Radioactivation background in satellites’ orbits

Our paper titled “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” has been published in Nuclear Instruments and Methods A. arXiv: https://arxiv.org/abs/1804.00827 ADS: http://adsabs.harvard.edu/abs/2018NIMPA.891…92O Hard X-ray observation must be conducted in a satellite’s orbit due to atmospheric absorption, and therefore suffers from significant backgrounds induced by cosmic rays and/or geomagnetically trapped charged particles. Hirokazu Odaka et al. have developed a new, effective, general-purpose framework of full Monte Carlo simulation of radioactivation background. We applied this framework to data measured with the Hard X-ray Imager onboard the …

Prof. Simionescu’s Seminar

We invited Professor Aurora Simionescu from ISAS/JAXA for a seminar. Her talk was titled “High Resolution X-Ray spectroscopy: Legacy from the Hitomi Observatory”, giving an excellent review on results of the Perseus Cluster observation with the Hitomi X-ray observatory and interesting science that XARM will bring us after its planned launch.

Discovery of a recombining plasma from the SNR HB 21

Our paper titled “Discovery of recombining plasma from the faintest GeV SNR HB 21 and a possible scenario of the cosmic ray escaping from SNR shocks” has been accepted for publication in PASJ. arXiv: https://arxiv.org/abs/1805.02882 ADS: http://adsabs.harvard.edu/abs/2018PASJ…70…75S Hiromasa Suzuki et al. revealed for the first time that a thermal plasma in the soft GeV gamma-ray SNR HB 21 had been suffered from rapid cooling very long time ago (~170 kyr), and is still on the way of recombination to the collisional ionization equilibrium. Furthermore, by comparing published data of 9 similar SNRs, the authors discovered a clue of a positive …