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.…

Read more

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.…

Read more

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…

Read more