9 citations · 18 across the 9 of their papers we have counts for
10 papers
XRISM Resolve Spectroscopy of GX 5-1: Constraints on Iron Spectral Features in a Luminous Neutron-Star Binary
Tasuku Hayashi, Shinya Yamada, Shun Inoue +11
GX 5-1 is one of the brightest persistent neutron-star low-mass X-ray binaries in the Galaxy and one of the classical Z sources accreting at luminosities close to or above the Eddi…
Chandra X-Ray Imaging and Spatially Resolved Spectroscopy of SN 1987A: Energy-Dependent Morphology of the Equatorial Ring
Yusuke Sakai, Shinya Yamada, Koji Mori +8
We present a systematic imaging and spatially resolved spectral study of SN 1987A using Chandra observations obtained between 1999 and 2025. By combining multiepoch ACIS and HETG d…
Formation of first star clusters under the supersonic gas flow -- III. Environmental trends and halo-to-halo scatter in the Pop III IMF
Shingo Hirano, Yusuke Sakai, Hideyuki Umeda
The first generations of stars ionised and enriched their host galaxies and seeded the growth of massive black holes. Models often assume that Pop III stellar masses in different m…
Spectral and photometric variability of SS 433 observed with XRISM and simultaneous optical and near-infrared telescopes
Yusuke Sakai, Shinya Yamada, Yuta Okada +36
We present results from coordinated multiwavelength observations of the SS 433, obtained with XRISM, optical telescopes, and near-infrared camera during 2024 April and 2025 March.…
XRISM High-resolution Spectroscopy of SS 433: Evidence of Decreasing Line-of-Sight Velocity Dispersion along the Jet
Megumi Shidatsu, Shogo Kobayashi, Yusuke Sakai +6
We report on the jet structure in SS 433 based on X-ray high resolution spectroscopy with the XRISM/Resolve. The source was observed over 5 days covering both inside and outside an…
Decadal brightening in the northeastern non-thermal filament of Cassiopeia A
Nao Kominato, Toshiki Sato, Yusuke Sakai +2
We present the decadal brightening of non-thermal emission flux in the northeastern filament of the young supernova remnant Cassiopeia A (Cas A), which highlights dynamic processes…
Arcsecond-Scale X-ray Imaging and Spectroscopy of SS 433 with Chandra HETG
Yusuke Sakai, Shinya Yamada, Haruka Sakemi +5
We present a spatial and spectral analysis of arcsecond-scale X-ray emission in SS 433 using zeroth-order data from Chandra High-Energy Transmission Grating (HETG) observations. Th…
Quantum Machine Learning for Identifying Transient Events in X-ray Light Curves
Taiki Kawamuro, Shinya Yamada, Shigehiro Nagataki +3
We investigate whether a novel method of quantum machine learning (QML) can identify anomalous events in X-ray light curves as transient events and apply it to detect such events f…
Dynamics of the intermediate-mass-element ejecta in the Supernova Remnant Cassiopeia A studied with XRISM
Shunsuke Suzuki, Haruto Sonoda, Yusuke Sakai +5
Supernova remnants (SNRs) provide crucial information of yet poorly understood mechanism of supernova explosion. Here we present XRISM high-resolution spectroscopy of the intermedi…
Kinematics of Supernova Remnants Using Multiepoch Maximum Likelihood Estimation: Chandra Observation of Cassiopeia A as an Example
Yusuke Sakai, Shinya Yamada, Toshiki Sato +2
Decadal changes in a nearby supernova remnant (SNR) were analyzed using a multiepoch maximum likelihood estimation (MLE) approach. To achieve greater accuracy in capturing the dyna…