Research Questions

Our publications

An ultra-short-period super-Earth and a sub-Neptune orbiting the K dwarf TOI-4311

01/07/2026 - Exoplanets

We report the discovery and characterization of the multiplanetary system around TOI-4311, a K dwarf kinematically between the Galactic thick disc and Hercules stream. TOI-4311 hosts an ultra-short-period super-Earth (P$sim$0.99 d, $1.376^{+0.077}_{-0.080}$ R$_{oplus }$) and a longer period sub-Neptune (P$sim$15 d, $2.47^{+0.12}_{-0.11}$ R$_{oplus }$) that was first detected in the Transiting Exoplanet Survey Satellite photometry.…

High-spectral-resolution X-Ray Observations of the Evolved Supermassive Stellar Binary System η Carinae: Fe Kα Band Profile Revealed with XRISM

01/06/2026 - High-Energy

The supermassive binary system, η Carinae, is experiencing enormous wind-driven mass loss at a rate unparalleled in the rest of the Galaxy. Their wind─wind collision (WWC) continuously produces shock heated, X-ray-emitting plasmas. The XRISM X-ray observatory observed the system in 2023 and 2024 when the X-ray emission began to increase toward periastron passage in 2025.…

Sensitivity of dry lava planet atmospheric emission spectra to changes in lava compositions

01/06/2026 - Exoplanets

The atmospheres of hot rocky exoplanets are among the first primary targets of the James Webb Space Telescope (JWST). Interpreting their atmospheric spectra requires understanding the link between silicate lava compositions and overlying atmospheres. We investigate the sensitivity of simulated emission spectra of dry lava planets to variations in oxide abundances in silicate melt. Our…

XRISM high-resolution X-ray spectroscopy of Cygnus X-1: Orbital and short-term variability of iron absorption

01/06/2026 - High-Energy

We present the first high-resolution spectroscopy of the black hole high-mass X-ray binary Cygnus X-1 with XRISM, including orbital-phase-resolved analyses and tentative evidence of short-term variability in the Fe K band on second timescales. Using data from the Performance Verification phase in 2024 April, we analyzed spectral variability across orbital phases with the Resolve microcalorimeter…

Resonant scattering at the center of the galaxy cluster PKS 0745-191 with XRISM

01/06/2026 - High-Energy

We report evidence of the resonant scattering effect at the center of the galaxy cluster PKS 0745-191 with XRISM. We analyzed XRISM/Resolve commissioning-phase observations of the distant cluster PKS 0745-191 ($z = 0.103$) with a $54$ ks exposure. The gain drift was corrected using the onboard modulated X-ray source (MXS), and spectra were extracted from…

State-selective Charge Exchange in the 6.43─42.86 keV u−1 14N6 Collision with He

01/06/2026 - High-Energy

The charge-exchange (CX) reaction between highly charged ions from coronal mass ejections and neutrals in Earth’s magnetosphere provides key diagnostics for understanding the dynamics of the Sun─Earth space environment. However, the accuracy of current astrophysical laboratory modeling is affected by the limited availability of reliable state-selective CX cross sections. Here, using a high-resolution cold-target recoil-ion…

Publications