Frederick Scott Porter

Aims. We investigated the phase-resolved X-ray spectral evolution of the high-mass X-ray binary Cen X-3 across the eclipse ingress and egress transitions, using two out-of-eclipse intervals as references, to constrain the properties of the absorbing material and the Fe K emitting regions with high-resolution XRISM/Resolve spectroscopy. Methods. The spectra were modeled with SPEX using a multicomponent model consisting of a fixed interstellar absorber, a local wind absorber with free temperature and velocity broadening, a power-law continuum, a blackbody component, and a disk-reflection component ( xskirtor ), which accounts for the fluorescent Fe K α and K β emission lines. Additional Gaussian components were included to model the ionized Fe XXV and Fe XXVI emission lines. We compared the orbital variation of the absorbing column with the predictions of a smooth CAK wind model and investigated the orbital variability of the Fe K α emission and its velocity broadening. Results. The local absorbing column density varies by nearly two orders of magnitude over the orbit, from N _H ^local = 4.25 × 10 ²² cm ⁻² during pre-ingress to 5.9 × 10 ²³ cm ⁻² at ingress. The excess absorption observed during ingress cannot be reproduced by a smooth stellar-wind model alone, suggesting the presence of a localized overdense structure along the line of sight. The Fe K α line width also varies with orbital phase, from ∼510 km s ⁻¹ during pre-ingress to ∼1400 km s ⁻¹ during egress, with intermediate, statistically indistinguishable values of ∼900 km s ⁻¹ measured during ingress and post-egress. The highly ionized Fe XXV and Fe XXVI emission is detected throughout the orbit, although fewer individual line components are resolved during ingress. Together, the absorption, fluorescence, and ionized emission diagnostics reveal a complex circumstellar environment in Cen X-3, with localized dense material and multiple reprocessing regions contributing to the observed orbital variability. Conclusions. These results provide a detailed view of the absorbing, emitting, and reprocessing environment during the eclipse transitions and demonstrate the capability of XRISM/Resolve to probe the geometry and kinematics of accretion environments in eclipsing high-mass X-ray binaries.

The coronal mass ejection (CME) arriving at Earth on 10 May 2024 caused the most intense geomagnetic storm in the last two decades, resulting in highly unusual cusp and magnetopause dynamics. We simulate soft X‐Ray emission due to solar wind charge exchange with exospheric neutrals to image the global dayside dynamics, focusing on the impact of a dense CME current sheet during the storm main phase. The magnetopause moves inward to , and the cusps manifest as nearly parallel emission ridges in X‐Ray. As the interplanetary magnetic field reverses, the cusp ridges move apart to higher latitudes for minutes after the reversal, addressing the open question of how the cusps evolve during and after northward turning of the IMF. Our work highlights soft X‐ray imaging enabling simultaneous observations of extreme solar‐wind impacts across multiple magnetospheric regions.

We present an analysis of the temperature structure of the Perseus cluster atmosphere using X-Ray Imaging and Spectroscopy Mission (XRISM) Resolve observations. The average temperature rises from 3.3 keV near the nucleus of NGC 1275 to 8 keV at 10′ (210 kpc), which is consistent with Chandra and XMM measurements. The velocity and velocity dispersion profiles are broadly consistent with those in XRISM Collaboration et al. While the gas at altitudes beyond ∼60 kpc can be modeled as a single temperature plasma, we find evidence for more than one gas phase in the inner ∼60 kpc. The hotter gas component, traced primarily by the Fe He α line, has a velocity dispersion of ≲140 km s ⁻¹ . We detect a cooler, ∼1.87–2.43 keV, gas component with a velocity dispersion of ∼300–400 km s ⁻¹ , a bulk velocity of ∼21–213 km s ⁻¹ with respect to the central galaxy, and a mass of 8 × 10 ⁹ –13 × 10 ¹⁰ M _⊙ . These ranges reflect large systematic uncertainties associated with modeling spatial-spectral mixing and the bright central point source. Potential low energy gain variations may add additional uncertainties. The cooler component is identified by broad wings in prominent emission lines, most notably S Ly α and Fe He α . This cooler component’s Mach number ∼0.73–0.96 and nonthermal pressure fraction of ∼22.9%–33.7% are much higher than found for the hotter gas. The cooler gas may be associated with merging halos along the line of sight, which formed the cool, sloshing spiral and/or cooling gas being disturbed by the radio jets and lobes.

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. This paper reports unprecedentedly high-resolution X-ray spectra in the Fe K α band between 6.2 and 7.1 keV, obtained with the Resolve X-ray microcalorimeter. The hydrogen-like (Ly α ) and helium-like (He α ) lines reveal three velocity components. Two of them are broadened with maximum velocities of 2000–3000 km s ⁻¹ , likely originating from the postshock companion wind. The other is relatively narrow, with a Gaussian broadening of only ∼290 km s ⁻¹ in 1 σ , which may originate from the postshock companion wind at the WWC stagnation point or penetrating the primary wind. The Fe fluorescent lines exhibit a moderate blueshift and broadening with velocities at 100–200 km s ⁻¹ , consistent with the primary wind’s velocity field. The spectra also confirm a Compton shoulder of the He α line complex for the first time. Both fluorescing and scattering spectral profiles indicate that the binary system is seen from the companion side during these observations. The flux ratio of the Compton-scattering emission to the fluorescent line suggests substantial hydrogen depletion of the primary wind, expected from CNO-cycled hydrogen nuclear fusion gas.

X-ray microcalorimeter space missions require an anti-coincidence detector to mitigate background events from Galactic Cosmic Rays (GCRs). These high-energy particles mimic an X-ray signal by depositing energy in the microcalorimeter absorber, with the amount proportional to their track length. An anti-coincidence detector, positioned below the main microcalorimeter array, identifies these background events and should respond quickly to a GCR signal, have a low threshold and high dynamic range, and use a similar readout scheme as the main detector array. For the proposed Line Emission Mapper (LEM) X-ray probe concept, a W and Al-based athermal phonon sensor design, originally developed for the Cryogenic Dark Matter Search, was adapted to cover a large Si substrate ( 14 sq. cm) with 12 parallel networks of these sensors. This initial prototype for the LEM mission was developed in collaboration with SLAC and Northwestern University, and tested at NASA Goddard Space Flight Center. The prototype demonstrated a combination of low threshold, high dynamic range, and millimeter-scale position discrimination, far exceeding all mission requirements. At the same time, detector modeling efforts were undertaken to understand the rich data sets produced by the prototype. In this work, we expand upon these modeling capabilities to explore new anti-coincidence particle detection designs enabled by the high performance of the LEM prototype. Using G4CMP, an add-on framework to Geant4 for phonon and charge transport in cryogenic detectors, we model the athermal phonon signals generated by GCR events and their collection as quasiparticles in the sensor network. We consider alternative sensor network layouts to maximize GCR event position discrimination, which could reduce false-coincidence events by localizing event rejection in the main array.

NewATHENA's X-ray Integral Field Unit (X-IFU) uses a large-format array of Transition Edge Sensor (TES) microcalorimeters coupled with absorbers made of gold and bismuth providing 4 eV FWHM resolution up to 7 keV in the 0.2 12 keV band. X-ray absorbers must be thick enough for photon absorption, maintain low heat capacity for energy resolution, and have good thermalization properties. The X-IFU requires total Quantum Efficiency (QE) of 96%, 87%, and 63% at 1, 7, and 9.5 keV, respectively. Optimal thicknesses are 1.05 μm gold and 5.5 μm bismuth to achieve 0.731 pJ/K at 90 mK and 87% QE at 7 keV. While typical TES absorbers are 3-4 μm thick, producing the required 5.5 μm Bi absorbers via standard electroplating creates enlarged grains and surface roughness. The increased roughness and grain size variability produced with our standard recipe have resulted in instances of 1) low energy spectral tails 2) spectral broadening of the energy resolution and 3) thermal shorts between pixels when a large grain bridges the gap between absorbers. In this study, we have introduced a new fabrication process and altered the morphology of the thick Bi through changes in the electroplating process. The process changes are intended to address all three issues as well as reduce particulate contamination observed on the finished detector arrays.

We present extended gas kinematic maps of the Perseus cluster based on a combination of five new XRISM/Resolve pointings observed in 2025 with four performance verification datasets from 2024, totaling a net exposure of 745 ks. To date, Perseus remains the only cluster that has been extensively mapped out to ≃0.7 r ₂₅₀₀ by XRISM/Resolve, while simultaneously offering sufficient spatial resolution to resolve gaseous substructures driven by mergers and active galactic nucleus (AGN) feedback. Our observations cover multiple radial directions and a broad range of dynamical scales, enabling us to characterize the kinematic properties of the intracluster medium up to a scale of ∼500 kpc. In the measurements, we detected high-velocity dispersions (≃300km s ⁻¹ ) in the eastern region of the cluster that are spatially coincident with the extended X-ray surface brightness excess and correspond to a nonthermal pressure fraction of ≃7 − 13%. The velocity field outside the AGN-dominant region can be effectively described by a single, large-scale kinematic driver based on the velocity structure function, which statistically favors an energy injection scale of at least a few hundred kpc. The estimated turbulent dissipation energy is comparable to the gravitational potential energy released by a recent merger, implying a significant role of turbulent cascade in the merger energy conversion. In the bulk velocity field, we observed a dipole-like pattern along the east-west direction with an amplitude of ≃ ± 200 − 300 km s ⁻¹ , indicating rotational motions induced by the recent merger event. This feature constrains the viewing direction to ≃30° −50° relative to the normal of the merger plane. Our hydrodynamic simulations suggest that Perseus has experienced at least two energetic mergers since redshift z ∼ 1, the most recent of which is associated with the radio galaxy IC310, in agreement with recent SRG/eROSITA findings. This study showcases exciting scientific opportunities for future missions with high-resolution spectroscopic capabilities (e.g., HUBS, LEM, and NewAthena).

We have investigated the dependence of superconducting tran sition parameters on the bilayer properties in Mo/Au transition edge sensors (TESs). We present measurements of the normalized partial derivatives of TES resistance with respect to temperature (α) and current (β), in several fabricated wafers with differing bilayer properties, but in a single TES design characterized at the same relative point in the transition. The results show α increases and β decreases approximately linearly with TES temperature T and normal state resistance Rn. To study these dependencies further, we measured the temperature dependence of the critical current Ic(T), and found it decreases approxi mately exponentially at high temperature. The slope of Ic(T) on a logarithmic scale correlates with Rn but is independent of the transition temperature. We examine to what extent these f indings can explain the observed T and Rn dependence of α and β. These results have implications for our understanding of the fundamental physics of the transition in these devices, and the reproducibility of TES performance resulting from small changes in bilayer fabrication.

The X-ray Integral Field Unit (X-IFU) on the NewAthena X-ray telescope will use a 1,504-pixel array of transition-edge sensor (TES) microcalorimeters, read out via time division multiplexing (TDM). To allow testing of multiplexer chips before TES integration, each unit cell includes a “TES-bypass” resistor that substitutes for a TES during characterization. After integration, this resistor remains as a high-resistance shunt: minimal for DC operation but can influence the frequency response due to its placement with the Nyquist inductor. We modeled the modified bias circuit, derived the small-signal response, and evaluated noise contributions, including Johnson noise from the bypass resistor. We analyzed the effects on pulse height, slew-rate, and energy resolution. Simulations were compared with measurements from prototype X-IFU microcalorimeters. Our results indicate that as long as the resistor value exceeds the TES dynamic resistance, performance is largely unaffected.