In this paper, we present extended gas kinematic maps of the Perseus cluster by combining five new XRISM/Resolve pointings observed in 2025 with four Performance Verification datasets from 2024, totaling 745 ks net exposure. 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 AGN feedback. Our observations cover multiple radial directions and a broad dynamical range, enabling us to characterize the intracluster medium kinematics up to the scale of ~500 kpc. In the measurements, we detect high velocity dispersions ($\simeq$300 km/s) in the eastern region of the cluster, corresponding to a nonthermal pressure fraction of $\simeq$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 observe a dipole-like pattern along the east-west direction with an amplitude of $\simeq\pm$200-300 km/s, indicating rotational motions induced by the recent merger event. This feature constrains the viewing direction to ~30$^\circ$-50$^\circ$ 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 latest associated with the radio galaxy IC310. This study showcases exciting scientific opportunities for future missions with high-resolution spectroscopic capabilities (e.g., HUBS, LEM, and NewAthena).

We perform a search for light sterile neutrinos using the data from the T2K far detector at a baseline of 295 km, with an exposure of 14.7 (7.6)$\times 10^{20}$ protons on target in neutrino (antineutrino) mode. A selection of neutral current interaction samples are also used to enhance the sensitivity to sterile mixing. No evidence of sterile neutrino mixing in the 3+1 model was found from a simultaneous fit to the charged-current muon, electron and neutral current neutrino samples. We set the most stringent limit on the sterile oscillation amplitude $\sin^2\theta_{24}$ for the sterile neutrino mass splitting \Delta m^2_{41}<3\times 10^{-3} eV$^2/c^4$.

We present high-resolution X-ray spectroscopy of the merging galaxy cluster Abell 3667 with \textit{XRISM}/Resolve. Two observations, targeting the cluster X-ray core and the prototypical cold front, were performed with exposures of 105 ks and 276 ks, respectively. We find that the gas in the core is blueshifted by $v_z\sim-200$ km s$^{-1}$ relative to the brightest cluster galaxy, while the low-entropy gas inside the cold front is redshifted by $v_z\sim 200$ km s$^{-1}$. As one moves further off-center across the front, the line-of-sight (LoS) velocity changes significantly, by $\Delta v_z=535^{+167}_{-154}$ km s$^{-1}$, back to the value similar to that in the core. There are no significant LoS velocity gradients perpendicular to the cluster symmetry axis. These features suggest that the gas forming the cold front is flowing in the plane oriented along the LoS, supporting an offset merger scenario in which the main cluster has passed in front of the subcluster and induced rotation of the core gas in the plane perpendicular to the sky. The region just inside the front exhibits the largest LoS velocity dispersion seen across two pointings, $\sigma_z\sim420$ km s$^{-1}$, which can be interpreted as a developing turbulence or a projection of the LoS velocity shear within the front. The large LoS velocity jump across the cold front, combined with the lack of Kelvin-Helmholtz instability on the surface of the front, suggests some mechanism to suppress it. For example, a magnetic field with $B>5\,\mu$G is required if the cold front is stabilized by magnetic draping.

Charged lepton flavor violation is forbidden in the Standard Model but possible in several new physics scenarios. In many of these models, the radiative decays $\tau^{\pm}\rightarrow\ell^{\pm}\gamma$ ($\ell=e,\mu$) are predicted to have a sizeable probability, making them particularly interesting channels to search at various experiments. An updated search via $\tau^{\pm}\rightarrow\ell^{\pm}\gamma$ using full data of the Belle experiment, corresponding to an integrated luminosity of 988 fb$^{-1}$, is reported for charged lepton flavor violation. No significant excess over background predictions from the Standard Model is observed, and the upper limits on the branching fractions, $\mathcal{B}(\tau^{\pm}\rightarrow \mu^{\pm}\gamma)$ $\leq$ $4.2\times10^{-8}$ and $\mathcal{B}(\tau^{\pm}\rightarrow e^{\pm}\gamma)$ $\leq$ $5.6\times10^{-8}$, are set at 90\% confidence level.

The physical processes behind astrophysical collisionless shocks, such as thermal relaxation and ionization after shock passage, remain poorly understood. To investigate these processes, we analyze the northeastern region of the Cygnus Loop with XMM-Newton. The electron temperature is found to increase towards the interior of the remnant ranging from 0.15-0.19 keV energy range within a spatial scale of 6 arcmin (or 1.27 pc at a distance of 725 pc) from the shock front. This can be explained well by a modified Sedov solution with radiative cooling. We also show that the ionization timescales determined from our spectroscopy are significantly larger than those estimated based on the electron density of the surrounding materials and the shock velocity. This excess can be qualitatively explained by a mixing of inner multiple plasma components with different ionization states due to turbulence.

While decades of observations in the TeV gamma-ray band have revealed more than 200~sources with radio or X-ray counterparts, there remain dozens of unidentified TeV sources, which may provide crucial information of cosmic ray (CR) accelerators. HESS J1626$-$490 is an unidentified TeV gamma-ray source but is expected to originate from CRs that escaped from the nearby supernova remnant (SNR) G335.2+0.1 and are interacting with dense interstellar clouds. To test this scenario, we scrutinize the properties of the SNR and search for non-thermal counterparts by analyzing observational data in the radio, X-ray, and GeV gamma-ray bands. From analysis of the H\,{\sc i} and $^{12}$CO ($J{=}1{-}0$) line data, we identify the cloud associated with the SNR and compare the morphologies of the cloud and the gamma-ray emission. The distance and age of the SNR are estimated to be $3.3 \pm 0.6$~kpc and ${\sim}5$~kyr, respectively. From X-ray and GeV gamma-ray data analyses, we find an extended GeV gamma-ray emission overlapping with the SNR and H.E.S.S. source regions but no X-ray emission. The location of the peak of the extended GeV emission changes from near the SNR at $\lesssim 1$~GeV to the H.E.S.S. source at $>10$~GeV. We find a spectral hardening at ${\sim}50$~GeV, which is consistent with the existence of two components in the gamma-ray emission. We find that a combination of emission from the escaped CRs and the SNR itself can reproduce the observed broadband spectrum, on the assumption that the SNR has accelerated protons to ${\gtrsim}100$~TeV in the past.

We present new measurements of the vertical density profile of the Earth's atmosphere at altitudes between 70 and 200 km, based on Earth occultations of the Crab Nebula observed with the X-ray Imaging Spectrometer onboard Suzaku and the Hard X-ray Imager onboard Hitomi. X-ray spectral variation due to the atmospheric absorption is used to derive tangential column densities of the absorbing species, i.e., N and O including atoms and molecules, along the line of sight. The tangential column densities are then inverted to obtain the atmospheric number density. The data from 219 occultation scans at low latitudes in both hemispheres from September 15, 2005 to March 26, 2016 are analyzed to generate a single, highly-averaged (in both space and time) vertical density profile. The density profile is in good agreement with the NRLMSISE-00 model, except for the altitude range of 70-110 km, where the measured density is about 50% smaller than the model. Such a deviation is consistent with the recent measurement with the SABER aboard the TIMED satellite (Cheng et al. 2020). Given that the NRLMSISE-00 model was constructed some time ago, the density decline could be due to the radiative cooling/contracting of the upper atmosphere as a result of greenhouse warming in the troposphere. However, we cannot rule out a possibility that the NRL model is simply imperfect in this region. We also present future prospects for the upcoming Japan-US X-ray astronomy satellite, XRISM, which will allow us to measure atmospheric composition with unprecedented spectral resolution of dE ~ 5 eV in 0.3-12 keV.

Cassiopeia A (Cas A) is the youngest known core-collapse supernova remnant (SNR) in the Galaxy and is perhaps the best-studied SNR in X-rays. Cas A has a line-rich spectrum dominated by thermal emission and given its high flux, it is an appealing target for high-resolution X-ray spectroscopy. Cas A was observed at two different locations during the Performance Verification phase of the XRISM mission, one location in the southeastern part (SE) of the remnant and one in the northwestern part (NW). This paper serves as an overview of these observations and discusses some of the issues relevant for the analysis of the data. We present maps of the so-called ``spatial-spectral mixing'' effect due to the fact that the XRISM point-spread function is larger than a pixel in the Resolve calorimeter array. We analyze spectra from two bright, on-axis regions such that the effects of spatial-spectral mixing are minimized. We find that it is critical to include redshifts/blueshifts and broadening of the emission lines in the two thermal components to achieve a reasonable fit given the high spectral resolution of the Resolve calorimeter. We fit the spectra with two versions of the AtomDB atomic database (3.0.9 and 3.1.0) and two versions of the SPEX (3.08.00 and 3.08.01*) spectral fitting software. Overall we find good agreement between AtomDB 3.1.0 and SPEX 3.08.01* for the spectral models considered in this paper. The most significant difference we found between AtomDB 3.0.9 and 3.1.0 and between AtomDB 3.1.0 and SPEX 3.08.01* is the Ni abundance, with the new atomic data favoring a considerably lower (up to a factor of 3) Ni abundance. Both regions exhibit significantly enhanced abundances compared to Solar values indicating that supernova ejecta dominate the emission in these regions. We find that the abundance ratios of Ti/Fe, Mn/Fe, \& Ni/Fe are significantly lower in the NW than the SE.

We present a time-averaged spectral analysis of the 2024 XRISM observation of the narrow-line Seyfert-1 galaxy MCG--6-30-15, taken contemporaneously with XMM-Newton and NuSTAR. Our analysis leverages a unique combination of broadband and high-resolution X-ray spectroscopy to definitively isolate and characterize both broad and narrow emission and absorption features in this source. The best-fitting model for the joint spectral analysis is very well described by reflection from the inner accretion disk illuminated by a compact corona, modified by multi-zone ionized absorption from an outflowing wind along the line of sight. The XRISM/Resolve data confirm that a strong, relativistically-broadened Fe K$\alpha$ emission line is required in order to obtain an adequate model fit. The Resolve data additionally verify the presence of a $v_{\rm out} \sim 2300$ km/s component of this outflowing wind, find tentative evidence for a $v_{\rm out} \sim 20,000$ km/s wind component, and indicate that the reflection from distant, neutral material may originate in a non-uniform structure rather than the traditional torus of AGN unification schemes. Though a rapid prograde black hole spin is statistically preferred by the best-fitting model, consistent with previous results, the AGN flux variability over the course of the observation complicates the interpretation of the time-averaged spectra. This insight, clarified by the combination of high signal-to-noise and high spectral resolution in the joint dataset, emphasizes the importance of time-resolved, high-resolution spectral analysis in unambiguously measuring the physical properties of variable AGN.

The expansion structure of supernova remnants (SNRs) is important for understanding not only how heavy elements are distributed into space, but also how supernovae explode. The ejecta expansion structure of the young core-collapse SNR Cas A is investigated, with Doppler parameter mapping of the Fe-K complex by the Resolve microcalorimeter onboard the X-ray Imaging and Spectroscopy Mission, XRISM. It is found that the Fe ejecta are blueshifted in the southeast (SE) and redshifted in the northwest (NW), indicating an incomplete shell structure, similar to the intermediate mass elements (IMEs), such as Si and S. The Fe has a velocity shift of $\sim1400$ km~s$^{-1}$ in the NW and $\sim2160$ km~s$^{-1}$ in the SE region, with the error range of a few 100s km~s$^{-1}$. These values are consistent with those for the IMEs in the NW region, whereas larger than those for the IMEs in the SE region, although the large error region prevented us from concluding which component has significantly higher velocity. The line broadening is larger in the center with values of $\sim$2000--3000~km~s$^{-1}$, and smaller near the edges of the remnant. The radial profiles of the Doppler shift and broadening of the IMEs and Fe indicate that the Fe ejecta may expand asymmetrically as IME ejacta, although the large error regions do not allow us to conclude it. Moreover, we see little bulk Doppler broadening of the Fe lines in the northeastern jet region whereas the IME lines exhibit significant broadening. No such narrow lines are detected in the NW region. These findings suggest an asymmetric expansion of the ejecta potentially driven by large-scale asymmetries originating from the supernova explosion. This interpretation aligns with the large-scale asymmetries predicted by models of neutrino-driven supernova explosions.

We have been developing event-driven SOI Pixel Detectors, named `XRPIX' (X-Ray soiPIXel) based on the silicon-on-insulator (SOI) pixel technology, for the future X-ray astronomical satellite with wide band coverage from 0.5 keV to 40 keV. XRPIX has event trigger output function at each pixel to acquire a good time resolution of a few $\mu \rm s$ and has Correlated Double Sampling function to reduce electric noises. The good time resolution enables the XRPIX to reduce Non X-ray Background in the high energy band above 10\,keV drastically by using anti-coincidence technique with active shield counters surrounding XRPIX. In order to increase the soft X-ray sensitivity, it is necessary to make the dead layer on the X-ray incident surface as thin as possible. Since XRPIX1b, which is a device at the initial stage of development, is a front-illuminated (FI) type of XRPIX, low energy X-ray photons are absorbed in the 8 $\rm \mu$m thick circuit layer, lowering the sensitivity in the soft X-ray band. Therefore, we developed a back-illuminated (BI) device XRPIX2b, and confirmed high detection efficiency down to 2.6 keV, below which the efficiency is affected by the readout noise. In order to further improve the detection efficiency in the soft X-ray band, we developed a back-illuminated device XRPIX3b with lower readout noise. In this work, we irradiated 2--5 keV X-ray beam collimated to 4 $\rm \mu m \phi$ to the sensor layer side of the XRPIX3b at 6 $\rm \mu m$ pitch. In this paper, we reported the uniformity of the relative detection efficiency, gain and energy resolution in the subpixel level for the first time. We also confirmed that the variation in the relative detection efficiency at the subpixel level reported by Matsumura et al. has improved.

The X-ray binary system Cygnus X-3 (4U 2030+40, V1521 Cyg) is luminous but enigmatic owing to the high intervening absorption. High-resolution X-ray spectroscopy uniquely probes the dynamics of the photoionized gas in the system. In this paper we report on an observation of Cyg X-3 with the XRISM/Resolve spectrometer which provides unprecedented spectral resolution and sensitivity in the 2-10 keV band. We detect multiple kinematic and ionization components in absorption and emission, whose superposition leads to complex line profiles, including strong P-Cygni profiles on resonance lines. The prominent Fe XXV He$\alpha$ and Fe XXVI Ly$\alpha$ emission complexes are clearly resolved into their characteristic fine structure transitions. Self-consistent photoionization modeling allows us to disentangle the absorption and emission components and measure the Doppler velocity of these components as a function of binary orbital phase. We find a significantly higher velocity amplitude for the emission lines than for the absorption lines. The absorption lines generally appear blueshifted by ${\sim}-500$-$600$km s$^{-1}$. We show that the wind decomposes naturally into a relatively smooth and large scale component, perhaps originating with the background wind itself, plus a turbulent more dense structure located close to the compact object in its orbit.

We report the radiation hardness of a p-channel CCD developed for the X-ray CCD camera onboard the XRISM satellite. This CCD has basically the same characteristics as the one used in the previous Hitomi satellite, but newly employs a notch structure of potential for signal charges by increasing the implant concentration in the channel. The new device was exposed up to approximately $7.9 \times 10^{10} \mathrm{~protons~cm^{-2}}$ at 100 MeV. The charge transfer inefficiency was estimated as a function of proton fluence with an ${}^{55} \mathrm{Fe}$ source. A device without the notch structure was also examined for comparison. The result shows that the notch device has a significantly higher radiation hardness than those without the notch structure including the device adopted for Hitomi. This proves that the new CCD is radiation tolerant for space applications with a sufficient margin.

We describe the in-orbit performance of the soft X-ray imaging system consisting of the Soft X-ray Telescope and the Soft X-ray Imager aboard Hitomi. Verification and calibration of imaging and spectroscopic performance are carried out making the best use of the limited data of less than three weeks. Basic performance including a large field of view of 38'x38' is verified with the first light image of the Perseus cluster of galaxies. Amongst the small number of observed targets, the on-minus-off pulse image for the out-of-time events of the Crab pulsar enables us to measure a half power diameter of the telescope as about 1.3'. The average energy resolution measured with the onboard calibration source events at 5.89 keV is 179 pm 3 eV in full width at half maximum. Light leak and cross talk issues affected the effective exposure time and the effective area, respectively, because all the observations were performed before optimizing an observation schedule and parameters for the dark level calculation. Screening the data affected by these two issues, we measure the background level to be 5.6x10^{-6} counts s^{-1} arcmin^{-2} cm^{-2} in the energy band of 5-12 keV, which is seven times lower than that of the Suzaku XIS-BI.

A search for the flavor-changing neutral-current decay $B^{+}\to K^{+}\nu\bar{\nu}$ is performed at the Belle II experiment at the SuperKEKB asymmetric energy electron-positron collider. The results are based on a data sample corresponding to an integrated luminosity of $63\,\mbox{fb}^{-1}$ collected at the $\Upsilon{(4S)}$ resonance and a sample of $9\,\mbox{fb}^{-1}$ collected at an energy $60\mathrm{\,Me\kern -0.1em V}$ below the resonance. A novel measurement method is employed, which exploits topological properties of the $B^{+}\to K^{+}\nu\bar{\nu}$ decay that differ from both generic bottom-meson decays and light-quark pair production. This inclusive tagging approach offers a higher signal efficiency compared to previous searches. No significant signal is observed. An upper limit on the branching fraction of $B^{+}\to K^{+}\nu\bar{\nu}$ of $4.1 \times 10^{-5}$ is set at the 90% confidence level.

We review a non-standard Big-Bang nucleosynthesis (BBN) scenario within the minimal supersymmetric standard model, and propose an idea to solve both ${}^{7}$Li and ${}^{6}$Li problems. Each problem is a discrepancy between the predicted abundance in the standard BBN and observed one. We focus on the stau, a supersymmetric partner of tau lepton, which is a long-lived charged particle when it is the next lightest supersymmetric particle and is degenerate in mass with the lightest supersymmetric particle. The long-lived stau forms a bound state with a nucleus, and provide non-standard nuclear reactions. One of those, the internal conversion process, accelerates the destruction of ${}^{7}$Be and ${}^{7}$Li, and leads to a solution to the ${}^{7}$Li problem. On the other hand, the bound state of the stau and ${}^{4}$He enhances productions of n, d, t, and ${}^{6}$Li. The over-production of ${}^{6}$Li could solve the ${}^{6}$Li problem. While, the over-productions of d and t could conflict with observations, and the relevant parameter space of the stau is strictly constrained. We therefore need to carefully investigate the stau-${}^{4}$He bound state to find a condition of solving the ${}^{6}$Li problem. The scenario of the long-lived stau simultaneously and successfully fit the abundances of light elements (d, t, ${}^{3}$He, ${}^{4}$He, ${}^{6}$Li, and ${}^{7}$Li) and the neutralino dark matter to the observed ones. Consequently parameter space both of the stau and the neutralino is determined with excellent accuracy.

We have been developing X-ray SOIPIXs, "XRPIX", for future X-ray astronomy satellites. XRPIX is equipped with a function of "event-driven readout", which allows us to readout signal hit pixels only and realizes a high time resolution ($\sim10\mu{\rm s}$). The current version of XRPIX suffers a problem that the readout noise in the event-driven readout mode is higher than that in the the frame readout mode, in which all the pixels are read out serially. Previous studies have clarified that the problem is caused by the cross-talks between buried P-wells (BPW) in the sensor layer and in-pixel circuits in the circuit layer. Thus, we developed new XRPIX having a Double SOI wafer (DSOI), which has an additional silicon layer (middle silicon) working as an electrical shield between the BPW and the in-pixel circuits. After adjusting the voltage applied to the middle silicon, we confirmed the reduction of the cross-talk by observing the analog waveform of the pixel circuit. We also successfully detected $^{241}$Am X-rays with XRPIX.

This article deals with flow of plane curves driven by the curvature and external force. We make use of such a geometric flow for the purpose of image segmentation. A parametric model for evolving curves with uniform and curvature adjusted redistribution of grid points will be described and compared.