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Our publications

01/02/2026 - High-Energy

XRISM view of a stellar flare: High-resolution Fe K spectra of HR 1099, an RS CVn-type star

A high-resolution X-ray spectroscopic observation was made of the RS CVn-type binary star HR 1099 using the Resolve instrument onboard XRISM for its calibration purposes. During the $sim$400 ks telescope time covering 1.5 binary orbit, a flare lasting for $sim$100 ks was observed with a released X-ray radiation energy of ${sim }10^{34}$ erg, making it…

01/02/2026 - High-Energy

Chemical composition and enrichment of the Centaurus cluster core seen by XRISM/Resolve

Context. Hot, X-ray emitting atmospheres pervading galaxy clusters (and groups) are rich in metals, which have been synthesised and released by asymptotic giant branch (AGB) stars, core-collapse supernovae (SNcc), and Type Ia supernovae (SNIa) over cosmic history. This makes the intracluster medium (ICM) an ideal astrophysical system to constrain its chemical composition, and hence ultimately…

01/01/2026 - High-Energy

The Feasibility of Using Fe XXIII Metastable Transitions as a Density Diagnostic for Low-mass X-Ray Binary Disk Winds

Low-mass X-ray binaries (LMXBs) occasionally show signs of outflowing material from the accretion disk. Studying these outflows can inform the understanding of the geometry of the systems, as well as the dynamics and energetics of accretion. One key variable for determining the location of these disk winds is the density of the outflowing material. In…

01/01/2026 - High-Energy

XRISM Observations of Accretion Disk Corona in Cyg X-2

We present the high-resolution X-ray spectrum of the Z-source Cygnus X-2, obtained with the X-Ray Imaging and Spectroscopy Mission (XRISM). The observations have enabled a precise characterization of the Fe─K emission lines from the accretion disk corona (ADC) and a possible detection of an ultrafast outflow. The ADC component has at least two distinct regions.…

01/01/2026 - High-Energy

XRISM Observations of the Prototypical Cold Front in A3667

We present high-resolution X-ray spectroscopy of the merging galaxy cluster A3667 with XRISM/Resolve. Two observations, targeting the cluster X-ray core and the prototypical cold front, were performed with exposures of 105 and 276 ks, respectively. We find that the gas in the core is blueshifted by vz ∼ −200 km s−1 relative to the brightest…

01/01/2026 - Exoplanets

HARPS-N, TESS, and CHEOPS discover a transiting sub-Neptune and two outer companions around the bright solar analogue HD 85426

We provide a detailed characterization of the planetary system orbiting HD 85426 (TOI-1774). This bright G-type star ($M_{ast }$: 0.99 $text{M}_{odot }$; $R_{ast }$: 1.13 $text{R}_{odot }$; age: 7.4 Gyr; V mag: 8.25) hosts a transiting sub-Neptune, HD 85426 b, with an orbital period of 16.71 d and a blackbody equilibrium temperature of $824^{+11}_{-11}$ K.…

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