JSPS core-to-core XRISM Science Workshop for Young Researchers 2026

Aug 24, 2026, 9:00 AM → Aug 25, 2026, 5:45 PM Asia/Tokyo

Theater Classroom, Comprehensive Research Building 1　（総合研究棟 シアター教室） (Saitama University (埼玉大学))

This is XRISM Science Workshop for young researchers in 2026, 
suponsored by JSPS core-to-core program.

Meeting Scope

The aim of this meeting is to provide a forum for young researchers, including graduate students, to discuss scientific results and future observation plans using the XRISM satellite. 

Date

The XRISM core-to-core Science Workshop for Young Researchers 2026 will be held on 24 - 25 August 2026.

Venue

The workshop will be held at Saitama University, Japan (Link to Access Map)The conference will be held on the 1st floor of Comprehensive Research Building 1 (総合研究棟), which is shown as No.21 in the PDF (Link to Campus Map PDF).

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Announcement

• We offer three registration categories. Their respective deadlines are listed below.

  • Type	Due Date
    Abstract Submission	17 July 2026 23:59 JST = 14:59 UT.  CLOSED. Thank you.
    Confluence Registration (on-site)	28 July 2026 13:00 JST = 4:00 UT. (You can modify the contents until the deadline) CLOSED. Thank you.
    Confluence Registration (remote only)	Welcome, Please register remote participatoin.
    Banquet registration	28 July 2026 13:00 JST = 4:00 UT. (You can modify the contents until the deadline) CLOSED. Thank you.

  • All participants in person are required to complete the “Conference Registration”;  i.e., presenters who submit abstracts (using “Submit new abstract”) are also required to complete conference registration (using “Conference Registration (in person)”).

  • We accept remote participants after on-site registration.

  • Late submissions received after the deadline will be rejected and not considered.

• There is no travel fee support from XRISM c2c.

Presentation type & Award

• Oral or Poster: Priority for oral presentations will be given to young postdoctoral researchers and late-stage PhD students. 

• Awards: Awards will be presented to postdoctoral researchers (PDs, who received their degrees within the past three years) and to graduate students who give oral or poster presentations.

• Notes

  • We expect young researchers to present their ideas for future X-ray observation plans and/or concepts for using archived data, based on observed XRISM data and/or scientific results and prospects from XRISM or other observatories (including both your own work and that of others).

  • Senior researchers (those who got their PhD more than 4 years ago) and undergraduated students may submit a poster presentation. Please note that they will not be considered for awards in general.

  • We plan to organize a series of lectures by senior researchers. Let’s enjoy science topics.

Message from Science Organizing Committee

• Due to scheduling constraints, we are unable to accommodate all requests for oral presentations. The presentation type (oral or poster) has been assigned based on career stage rather than scientific significance. We look forward to seeing you at the workshop and let’s discuss and enjoy XRISM science.

Long-term international research visiting programs (c2c若手長期派遣事業)

• This program is limited for young researchers in Japan.
• Two of the award-winning researchers  (limited to those based in Japan) will also receive the opportunity to travel and conduct research abroad.

 

Registration fee

• Free for students, and 500 JPY for PD/Staff
• This is used for coffee break. Your contributions welcome.
• Please pay the fee at the registration desk

  • Type	Registration fee	Banquet fee
    Students	0 JPY	6,000 JPY
    PD/Staff	500 JPY (or more )	6,000 JPY

 

 

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Sponsors

JSPS core-to-core program for XRISM
https://www.oai.saitama-u.ac.jp/core2core/index.html

 

Link

• X-ray Imaging and Spectroscopy Mission, XRISM (JAXA)
• X-ray Imaging and Spectroscopy Mission, XRISM (NASA)
• X-ray Imaging and Spectroscopy Mission, XRISM (ESA) 
• XRISM Researchers WWW (JAXA)
• X XRISM_jp
• XRISM Archive Data View (JAXA)

 

XRISMc2cWS2026_abstract_book.pdf

Mon, August 24

Welcome: XRISM Science Heighlights & Future

Convener: Makoto Tashiro (Saitama University)

1 Welcome to XRISM c2c workshop

Speaker: Dr Yukikatsu Terada (Saitama University / JAXA)

XRISMc2cWS2026_welcome_YTerada_v20260824.pdf

2 XRISM Science Highlights: XRISM Spectroscopy of Nearby AGNs

XRISM is opening a new window on the X-ray spectroscopy of active galactic nuclei (AGNs), providing unprecedented views of the physical and chemical properties of gas in the vicinity of supermassive black holes. In this talk, I will review selected recent XRISM results on AGNs. Possible topics include the geometry and kinematics of circumnuclear material, elemental abundance ratios, and highly ionized outflows such as ultra-fast outflows (UFOs). Rather than attempting a comprehensive overview, I will highlight several representative results and discuss how high-resolution spectroscopy with XRISM is refining our picture of the complex environments around accreting supermassive black holes.

Speaker: Dr Shoji Ogawa (Tokyo University of Science)

3 XRISM Science Highlights: Beyond the Milky Way

While many presenters at this conference are confined within the virial radius of the Milky Way, and even more seem to reside within the Galactic disk (surprisingly!), the scientific rationale of XRISM encompasses the circulation of matter and the transfer of energy on a cosmic scale. Achieving these objectives undoubtedly requires observations of extragalactic objects, including galaxies, galaxy clusters, and the massive black holes at their centers. In this talk, I will highlight scientific outcomes from XRISM's high-resolution spectroscopy, from the initial performance-verification phase through nominal operations, and discuss how they are changing our view of the dynamics, energetics, and chemical evolution of extragalactic systems. A small disclaimer: I have spent much of my career studying the intracluster medium in galaxy clusters, so my choice of highlights may inevitably be somewhat confined in great potential wells. Most importantly, I hope that all of you, the XRISM native generation, will come up with fresh ideas throughout this conference to maximise XRISM's potential and drive remarkable scientific advances in the near future.

Speaker: Dr Kotaro Fukushima (Tokyo University of Science)

XRISM_highlights_c2c.pdf

4 XRISM Scientific Strategy for the Extended Phase

XRISM has opened a new era of high-resolution X-ray spectroscopy, providing unprecedented measurements of the dynamics, composition, and physical state of astrophysical plasmas. As the mission enters its extended phase, the key question is how to maximize its scientific legacy beyond the achievements of the initial observing program. In this talk, I will present the scientific strategy for XRISM’s extended operations, highlighting the major questions that can be uniquely addressed by the mission and the role of systematic observations in answering them.

Speaker: Hiroya Yamaguchi (ISAS/JAXA)

12:00 PM Lunch Break

Science Talk: Stars and Compact Objects

Convener: Dr Yukikatsu Terada (Saitama University / JAXA)

5 XRISM/Resolve spectroscopy of the wind-wind collision shock in WR 140: Implications for plasma cooling toward dust formation

Cosmic dust is essential for star and planet formation, the formation of molecules, and the chemical evolution of galaxies. However, its primary production sites and formation mechanisms remain poorly understood. Dust-forming Wolf-Rayet (WR) binaries provide ideal laboratories for investigating dust formation conditions (Williams+2009). Among them, WR 140 is an ideal target because its orbital parameters are well constrained (Monnier+2011), allowing observations during both dust-forming and dust-free phases (Lau+2022). Our long-term goal is to elucidate the cooling of the wind-wind collision plasma to dust formation temperatures through hydrodynamic simulations. As a first step, we analyzed the XRISM/Resolve spectrum of WR 140 taken shortly before periastron (ϕ = 0.983). We developed an emission model for the He-like and H-like lines of Fe, Ar, and S to determine their emitting regions and constrain the spatial distribution of plasmas with different ionization states. The results indicate that the shocked plasmas remain largely unmixed near the shock apex and flow as two distinct fluids. Furthermore, the plasma is still ionizing as it flows downstream, rather than cooling as conventionally assumed. These results provide key constraints for future modeling of plasma cooling toward dust formation.

Speaker: Asca Miyamoto (JAXA/ISAS)

6 XRISM Spectroscopy of X-ray-Irradiated Protoplanetary Disks: First Observational Results of Elias 29 and Future Prospects

Pre-main-sequence stars exhibit strong magnetic activity (e.g., Koyama
et al. 1996), and increasing attention has been paid to how the resulting X-rays affect the chemical evolution of surrounding
protoplanetary disks (e.g., Washinoue et al. 2024). Although theoretical
and simulation studies have advanced rapidly, observational verification
remains limited.

The Fe Kα emission line at 6.4 keV is frequently detected in X-ray
observations of pre-main-sequence stars (e.g., Tsujimoto et al. 2005).
It is thought to arise when X-rays from the central star photoionize
material in the surrounding disk. Because its centroid energy depends on
the ionization parameter, which is determined by the distance from the
star and the disk density, precise measurements can constrain how deeply
stellar X-rays penetrate the disk. The line therefore provides an
important observational probe of X-ray-driven disk chemistry.

With its unprecedented energy resolution, XRISM has enabled precision
spectroscopy of Fe Kα emission from protoplanetary disks for the first
time. As a first step, we observed Elias 29, a Class I protostar in the
Ophiuchus star-forming region, through the XRISM Cycle 1 General
Observer program. However, planet formation proceeds from the Class 0 to
Class III stages, and current XRISM observations sample only one part of
this evolutionary sequence. We present the XRISM results for Elias 29
and explore future observing strategies to probe X-ray irradiation and
disk evolution across different stages of planet formation. XRISM will
open a new interdisciplinary frontier between X-ray astronomy and planet
formation.

Speaker: Shun Inoue (Kyoto University)

7 Phase-Resolved Fe K-Shell Line Diagnostics of Accreting White Dwarfs Enabled by XRISM/Resolve: Orbital Dynamics and Accretion-Column Geometry in EX Hydrae

Accreting white dwarfs (WDs) in close binaries are key laboratories for studying binary evolution and accretion physics, yet their masses and accretion structures remain difficult to determine. In magnetic WDs, accreting gas is channeled toward the poles, forming accretion columns in which shock heating produces hot plasma that emits thermal X-rays. The orbital- and spin-phase dependence of this emission carries information about WD motion and the structure of the rotating accretion flow. High-resolution X-ray spectroscopy can therefore provide powerful constraints on WD masses and accretion geometry.

We present an 83 ks XRISM observation of EX Hydrae, an eclipsing binary hosting a magnetic WD. Resolve separates the Fe XXV $K\alpha$ components, Fe XXVI Ly$\alpha$ doublet, and fluorescent Fe $K\alpha$ line. The Fe XXV $K\alpha$ components show coherent orbital modulation, the first detection in individual Fe K-shell lines from an accreting WD. Fitting the modulation gives a radial-velocity semi-amplitude $K_1 = 58.1 \pm 8.5~\mathrm{km~s^{-1}}$, consistent with optical/ultraviolet measurements. Combined with literature orbital parameters, this yields a WD mass $M_1 = 0.79 \pm 0.04~M_\odot$. This demonstrates a complementary X-ray route to dynamical mass measurements with individual Fe K-shell lines, potentially applicable to non-magnetic accreting WDs.

We also find that the Fe XXVI Ly$\alpha_1$/Ly$\alpha_2$ intensity ratio varies with WD spin phase. Because Ly$\alpha_1$ has a larger oscillator strength than Ly$\alpha_2$, resonance scattering can make the ratio sensitive to viewing-angle-dependent optical depth through the accretion column. We are testing this interpretation with the radiative-transfer code SKIRT to constrain the line-forming region and three-dimensional column structure.

Speaker: Yuken Ohshiro (The University of Tokyo)

8 Accretion Geometry of Wind-fed X-Ray Binaries

An X-ray binary is a system where mass and angular momentum are transferred from a companion star to a compact object through accretion, resulting in the emission of X-rays. We use spectroscopic techniques to measure its accretion geometry.
　AX J1910.7+0917 is known as the slowest X-ray pulsar, with a spin period of ~10 hr. In the PV phase, we serendipitously detected an outburst from AX J1910.7+0917 on Xtend's FoV. The sharp flares and a Fe line are confirmed, suggesting the system is a wind-fed supergiant X-ray binary. These characteristics could be explained by interactions with a quasi-spherical shell. In XRISM AO3, we will observe the second-slowest X-ray pulsar, 4U1954+319, to measure the shell geometry in detail based on the line structure by Resolve.
　Doppler Tomography is a powerful method for indirectly imaging a binary system. It reconstructs a velocity map from variations in line profiles accompanied by orbital modulation. In the context of the accretion geometry, the Fe Kα emission line serves as an effective tracer for cold matter. We will observe wind-fed X-ray binaries 4U1538-522 and 4U1700-37 with a full orbit in XRISM AO3 to obtain the velocity map of the line (PI: Yoshimoto).
　As stated above, we perform various approaches to reveal the accretion geometry of wind-fed X-ray binaries. We present the results of the Xtend observation and introduce our future observation plans using the high-energy resolution of Resolve.

Speaker: Dr Marina Yoshimoto (Ehime University)

9 Observational Study of Stellar Wind Dynamics in the High-mass X-ray binary Cygnus X-3 through High-Resolution X-ray Spectroscopy with XRISM

Cyg X-3 is a high-mass X-ray binary (HMXB) consisting of a Wolf–Rayet (WR) star and a compact object. The dense stellar wind from the WR star is photoionized by X-rays from the compact object, producing numerous emission and absorption lines that probe the wind structure. Owing to the high spectral resolution of XRISM, several tens of spectral lines have been detected, providing effective diagnostics of the wind velocity and density distributions.
We measured the orbital modulation of the Doppler shifts of the Fe, Ca, Ar, and S Lyα emission lines and compared them with photoionization equilibrium calculations using the CLOUDY code. The results suggested that the Fe Lyα line originates near the compact object and traces its orbital motion, whereas the S Lyα line arises from a more extended region and reflects the radially outflowing stellar wind.
We further investigate the orbital modulation of emission-line widths. Cross-correlation analysis shows that the widths of the Fe, Ca, and Ar Lyα lines peak near orbital phase 0.25, while the S Lyα line exhibits no comparable periodicity. We also measured the orbital modulation of absorption-line strengths and Doppler shifts for each element. We compared these results with previous studies and three-dimensional radiative transfer simulations with the spherically symmetric stellar wind using MONACO (Odaka et al. 2011). We discuss which observed features can be explained by the spherical wind model and the asymmetric wind structure implied by the remaining discrepancies.

Speaker: Dr Tomohiro Hakamata (ISAS/JAXA)

10 Improved He-like Ka Line Diagnostics for Photoionized Plasmas

The helium-like K$\alpha$ line complexes are valuable diagnostics of electron density, temperature, and ionization conditions of astrophysical plasmas. The ratios of these lines can be altered by the presence of lithium-like ions, both through inner-shell ionization as well as resonant Auger-Meitner Destruction (RAD), in which the He-like intercombination lines are diminished by line absorption from near-coincident Li-like ($1s 2s 2p \rightarrow 1s^2 2s$) lines. We modeled the effect of increased Li-like presence on the He-like line ratios $\mathcal{R} \equiv z/(x+y)$ and $\mathcal{G} \equiv (x+y+z)/w$ for astrophysically important ions in a photoionized plasma, by solving the steady-state rate equations as a function of Li-like column density $N_{Li}$, He-like column density $N_{He}$, velocity dispersion $\sigma_v$, electron density $n_e$, and UV photoexcitation rate $\Phi$. We also define and analytically solve for a ratio $\mathcal{Q} \equiv (q+r)/w$, which is a diagnostic of the Li-like column density. We find that a high Li-like column density can significantly modify $\mathcal{R}$ and $\mathcal{G}$ through both enhancement of $z$ and suppression of $x$ and $y$, and that the effects of RAD are strongly dependent on the energy difference between the emitting and absorption transitions for a given element. Due to this dependence, we stress the importance of a carefully curated database as a reference for transition energies. Our diagnostic framework is suitable for application to spectra of active galactic nuclei and X-ray binaries observed by the $\it{XRISM}$ Resolve, $\it{XMM-Newton}$ RGS, and $\it{Chandra}$ HETGS.

Speaker: Gabriel Grell (NASA Goddard Space Flight Center)

3:00 PM Coffee break

Poster Presentation: (Block 1)

11 A Possible Overionized Disk Wind in 4U 1630−472: Prospects for Future High-Resolution Spectroscopy with XRISM/Resolve

High-inclination black hole X-ray binaries (BHXRBs) provide unique opportunities to investigate highly ionized disk winds. 4U 1630−472 is one of the most active BHXRBs, exhibiting outbursts repeatedly with an interval of about 600 days. Previous observations have revealed highly ionized absorption lines attributed to disk winds in this source. Here, we report a possible signature of a highly ionized plasma, potentially associated with a disk wind, inferred from X-ray continuum variability rather than absorption lines. During the brightest phase of the 2012 outburst, one of the largest recorded from this source, we detected X-ray flux drops of approximately 50% lasting about one day in the MAXI/GSC and Swift/BAT light curves. This variability occurs on a timescale shorter than the overall outburst evolution but much longer than the typical short-term variability observed in BHXRBs. Comparison of the X-ray spectra obtained before, during, and after the flux drops revealed that, during the flux-drop events, only the X-ray flux decreased, while the spectral shape remained nearly unchanged. We interpret this behavior as Thomson scattering by almost fully ionized gas associated with a disk wind crossing our line of sight and reducing the apparent X-ray flux. Finally, we discuss the prospects for detecting disk-wind absorption lines and their variability with XRISM/Resolve during state transitions near the outburst peak in BHXRBs, together with observational signatures of the possible overionized wind component inferred from this study.

Speaker: Chulsoo Kang (Ehime University)

12 Accretion Environments in X-ray Binaries Proved by Mildly-ionized Fe Absorption Lines

In X-ray binaries, accreted plasma is photoionized by intense X-ray radiation from the vicinity of the compact object. While the geometry and dynamics of this plasma have been traditionally probed via absorption lines from highly ionized Fe ions, the recent detection of mildly-ionized Fe XVII-XXIV ions by XRISM/Resolve significantly expands our diagnostic capabilities. Resolving absorption lines from these intermediate-charge ions allows us to probe a much wider range of ionization parameters, while their density-sensitive metastable levels provide an independent constraint on $n$, thereby uniquely determining the distance to the absorbers. To exploit this capability across different accretion environments, we constructed models of individual absorption lines of each ion, which allowed us to investigate the detailed velocity, ionization, and density structures. We applied these models to the high-mass X-ray binary Cygnus X-3, focusing on the radial and azimuthal structure of the stellar wind. We then expanded this analysis to spectra obtained from dipping low-mass X-ray binaries. Notably, these mildly-ionized ions are detected exclusively during dipping phases, confirming their origin within the accretion disk bulge. Furthermore, the absorption lines exhibit complex profiles attributable to transitions from metastable levels. The derived parameters indicate a high electron density within the bulge; specifically, for 4U 1624-49, the first observation yields a density of 12.5 < log $n$ < 13.6 (90% confidence), while the second yields log $n$ > 13.9 (90% confidence). In this poster, we discuss the resulting plasma structures across these diverse X-ray binaries, in conjunction with radiative transfer calculations.

Speaker: Daiki Miura (The University of Tokyo, ISAS / JAXA)

13 Constraining Hydrogen Column Densities of Galactic Center Molecular Clouds Using the Fe Kα Compton Shoulder Observed with XRISM/Resolve

Characteristic X-ray emission from neutral iron is observed in the Galactic Center (Koyama et al. 1996, PASJ, 48, 249). Its spatial distribution is correlated with molecular clouds, and its main origin is thought to be photoionization by past flares of the supermassive black hole Sagittarius A (Sgr A). Compton scattering of the neutral iron $K\alpha$ line within molecular clouds produces a low-energy feature called the Compton shoulder (CS), which is an important diagnostic of the cloud density and geometry. Using XRISM/Resolve, we searched for the CS in several Galactic Center clouds. We detected the CS at about $4\sigma$ significance from a cloud approximately $9~\rm{arcmin}$ east of Sgr A and constrained the CS fluxes in the other regions.
We performed Monte Carlo simulations of uniform-density spherical clouds and calculated CS-to-neutral-iron-line intensity ratios for various $N_{\rm H}$ values. Comparison with the observed ratios constrained $N_{\rm H}$ in most regions. We also measured the Doppler velocities of the neutral Fe lines and identified the corresponding molecular clouds using $^{13}$CO($J=1$--$0$) data obtained with the Nobeyama 45-m radio telescope. Assuming local thermodynamic equilibrium (LTE), we constrained the hydrogen column densities from the radio data. We also measured the absorbing column densities through broadband X-ray spectral fitting. We then compared the $N_{\rm H}$ values derived from the CS, the LTE analysis, and the X-ray spectra. We propose follow-up observations to tighten the constraints on $N_{\rm H}$, which may help reveal the three-dimensional relationship between the molecular clouds emitting neutral Fe lines and Sgr A.

Speaker: Kentaro Okada (Kindai University)

14 Exploring the Accretion Disk-Corona Geometry of NGC 4151 with XRISM and IXPE

To explain the hard X-ray emission of AGN, an extremely hot "corona" (electron
temperature ~100 keV) has been introduced, but its heating mechanism remains
unknown. Determining the disk-corona geometry is key to understanding this heating
and cooling, and spectroscopy and polarimetry are the two most powerful probes:
spectroscopy uses the Fe fluorescence line to constrain the inner disk radius and
irradiation profile, while polarimetry gives independent geometric information via
photon scattering in the corona. NGC 4151, an X-ray-bright Seyfert galaxy, is an ideal
target. This object is one of the few AGN with significant IXPE polarization (Gianolli et
al. 2023) and a high-statistics XRISM/Resolve Fe line (XRISM Collaboration 2024).
However, no model has reproduced both observations simultaneously.
Using the Monte Carlo code MONACO (Odaka et al. 2011), we built a framework
computing polarization and spectra simultaneously from 3D distributions of ionized and
neutral matter, including inverse-Compton scattering of disk UV/optical photons.
Assuming a thin disk with slab- or lamppost-type coronae, we compared computed
polarization and Fe lines with observations. In our simulation, the lamppost model fails
to reproduce the observed polarization angle, while the slab model leads to excessive
Comptonization when the corona inner radius is comparable to that of the disk and the
vertical optical depth is ~1. In this presentation, we clarify what each model can and
cannot explain, giving qualitative constraints on NGC 4151's disk-corona structure.

Speaker: Haruki Kuramoto (The University of Osaka)

15 Neutron-Rich Ejecta from a Low-Energy Explosion: An XRISM View of the Supernova Remnant G349.7+0.2

In core-collapse supernovae, the Ni/Fe ratio is an indicator of the neutron excess near the core—set by electron capture and neutrino interactions—and thus serves as a probe of the explosion mechanism. This excess is imprinted on the iron-group elements: neutron-rich material yields stable isotopes such as ⁵⁸Ni rather than ⁵⁶Ni, so a high ratio directly signals neutron-rich ejecta. In particular, a high Ni/Fe ratio is reproduced in theoretical models of supernovae from low-mass (8–10 M⊙) stars. We observed G349.7+0.2 with XRISM in the AO1 cycle. Earlier Suzaku CCD spectra could not separate the Ni Kα line from the neighboring Fe Kβ line, but the high resolution of XRISM reveals a line profile that only Ni can reproduce, giving a Ni/Fe ratio of ~11 times the solar value. XRISM also measures the line broadening for the first time; with the plasma radius, this implies a low explosion energy of <10⁵¹ erg, clearly lower than in typical core collapse supernova remnants, supporting a low-mass-star origin. In this talk, we discuss the explosion mechanism and progenitor of G349.7+0.2. As an outlook, we regard this as a first step toward understanding how the Ni/Fe ratio traces the physics of core-collapse explosions. Whether the high Ni/Fe and low explosion energy of G349.7+0.2 reflect a broader trend or are merely an outlier is a key question, which a systematic XRISM survey of all observable remnants would address.

Speaker: Atsuya Uchida (Kyoto university)

16 Precise X-ray Spectroscopic Observations with XRISM for Independent Measurement of Neutron Star Mass and Radius

Neutron stars (NSs) are degenerate stars that support their own mass by the degeneracy pressure of neutrons. They are key research objects not only in astrophysics but also in nuclear physics, especially in investigations of neutron-rich nuclei. Constraining their mass and radius observationally is important for constraining the equation of state of nuclear materials inside NSs.
One effective approach to constraining mass and radius is to use absorption lines generated in the NS atmosphere during thermonuclear bursts in low-mass X-ray binaries (LMXBs) and to drive the mass-to-radius ratio from the gravitational redshift (Cottam et al., 2002, Nature, 420, 51-54). However, in principle this method cannot determine mass and radius separately. To address this issue, we aim to search for rotationally induced splitting of these absorption features with XRISM/Resolve. If we successfully detect such splitting features, it will provide three independent observables: the gravitational redshift, the energy separation between the split absorptions, and the ratio of their line depths. This, in turn, would allow us to break the degeneracy among mass, radius, and system inclination.
We first select feasible NS-LMXBs with known rotation periods, masses of approximately $1.4M_{\odot}$, and peak X-ray fluxes (2-10 keV) of $~10^{-9}\;\mathrm{erg}\;\mathrm{s}^{-1}\;\mathrm{cm}^{-2}$. Our estimations indicate some targets exhibit detectable split absorption feature with Resolve. We also highlight outstanding issues, including establishing a robust method to accurately derive inclination information from the spectra to clarify the physical origin of the absorption lines.

Speaker: Kaname Ando (Saitama University)

17 Probing the Distribution of Neutral Material in Vela X-1 through the Fe Kα Pulse Response Observed with XRISM

The physics of mass transfer and accretion flows in High-Mass X-ray Binaries (HMXBs) is the key to understanding binary evolution, including the formation of gravitational-wave progenitors. In particular, the neutral Fe Kα fluorescence lines originating from cool gas in stellar winds and accretion flows serves as a tracer of the matter distribution within these systems. Vela X-1, consisting of a B-type supergiant and a neutron star, is one of the best-studied HMXBs. Its strong Fe Kα emission at 6.4 keV makes it an ideal target for investigating accretion structures. In this study, we analyzed three XRISM observations of Vela X-1 obtained at different orbital phases. Using the high energy resolution of the Resolve spectrometer, we isolated the Fe Kα line from the underlying continuum and compared its pulse profile with that of the hard X-ray continuum emitted by the rotating neutron star. We detected a pulse response of the Fe Kα line at all observed orbital phases and found that the pulse-phase delay varies systematically with orbital phase. Based on these results, we infer that the Fe Kα emission region is located in a specific azimuthal direction relative to the neutron star. This finding suggests that the cool gas responsible for the fluorescent emission is locally distributed within the asymmetric accretion wake formed by the orbital motion.

Speaker: Kota Satomura (The University of Tokyo, ISAS / JAXA)

18 Space-Readiness Demonstration of TES Microcalorimeters in a Radiation Environment up to 200 keV

Transition-edge sensor (TES) microcalorimeters offer higher thermometric sensitivity than semiconductor-based microcalorimeters such as XRISM/Resolve, enabling superior energy resolution and scalable multiplexed arrays for future X-ray and soft gamma-ray missions. To advance their technological readiness, we operated approximately 200 TES pixels with microwave SQUID multiplexing in the accelerator environment at J-PARC/MLF and calibrated their response up to about 200 keV using $^{57}$Co, $^{139}$Ce, and $^{169}$Yb sources. Energy resolutions below 100 eV were achieved near 166 keV. Multi-pixel waveform analysis revealed correlations between primary events, neighboring-pixel responses, and beam-related crosstalk. Event screening reduced the high-energy tail of the 122 keV $^{57}$Co line and improved the energy resolution, demonstrating robust TES operation in a radiation environment relevant to future space missions. In parallel, we are developing practical experience with large TES arrays while conducting phase-resolved XRISM/Resolve spectroscopy of Cygnus X-1, one of the brightest XRISM targets.

Speaker: Shintaro Kaneko (Rikkyo Univ.)

19 Spatially Resolved Temperature Diagnostics of the Intracluster Medium in Abell 3571 with XRISM/Resolve

Accurate measurements of the intracluster medium (ICM) temperature are essential for understanding the dynamical state of galaxy clusters. XRISM/Resolve provides temperature diagnostics based on Fe K-shell line ratios independent of conventional collisional ionization equilibrium (CIE) model fitting. However, discrepancies between observed and CIE-predicted intensities of the Fe XXV Heα x,y and Fe XXVI Lyα1,2 lines have been reported in A2029 and Coma (XRISM Collaboration 2025a,c), and their origins remain unclear.


The central region of Abell 3571 (kT ~ 7 keV) exhibits a north-south elongated X-ray morphology suggestive of gas sloshing. Using three Resolve pointings, we performed spatially resolved Fe-line diagnostics and determined the ICM temperature.

We found Fe-line intensity-ratio anomalies similar to those in A2029 and Coma.
The average Lyα2/Lyα1 intensity ratio was 0.7 ± 0.2 (1σ scatter), exceeding the CIE prediction of ~ 0.5. No spatial correlation was found. These anomalies introduce systematic uncertainties in temperature diagnostics. Temperatures derived from the Lyα1/z ratio (6.5 ± 0.1 keV on average) agreed with continuum-based values, whereas those derived from the Lyα2/z ratio exceeded them by up to 30%. One possible explanation is that unresolved DR satellite lines absent from current atomic codes enhance the Lyα2 intensity.

We will extend this analysis to a larger sample of galaxy clusters using the growing XRISM archive. A systematic investigation of the line-ratio anomalies will provide a more robust understanding of their physical origin and improve the accuracy and reliability of plasma diagnostics based on high-resolution X-ray spectroscopy in the XRISM era and beyond.

Speaker: Leo Hirata (The University of Tokyo, ISAS / JAXA)

20 Velocity Measurement of Reflected Shock Waves in SNR LMC N63A Using the XRISM Satellite

Supernova remnants(SNR) can generate reflected shock waves when they collide with molecular clouds. The existence of such reflected shock waves has been suggested for various celestial objects based on indirect evidence, such as temperature structures. However, there are currently very few examples of direct observations of plasma motion associated with reflected shock waves. Therefore, we focused on LMC N63A, located in the Large Magellanic Cloud(LMC). ALMA CO observations have revealed that a molecular cloud exists in front of the N63A(Sano et al. 2019), and X-ray observations using instruments such as Chandra/ACIS have suggested the presence of a reflected shock wave based on its temperature structure(Sano et al. 2019, Suzuki et al. in prep).
In this study, we analyzed X-ray spectra obtained with the XRISM/Resolve. The results revealed a cool plasma($kT_e\sim0.68$ keV) and a hot plasma emitting the Fe-K line($kT_e\sim1.8$ keV). Furthermore, we successfully measured the Doppler shifts of each plasma for the first time. Considering the proper motion of the LMC, we found that the cool plasma is blueshifted at $90\pm30$ km/s, while the hot plasma is redshifted at $230\pm40$ km/s. This motion direction of the hot plasma is consistent with the scenario in which a reflected shock wave was generated by the interaction with molecular clouds at the front of the remnant. Furthermore, assuming that the line width is dominated by thermal broadening, we estimated the Fe ion temperature to be $60\pm1$ keV and the reflected shock wave velocity to be $750\pm90$ km/s from Fe-K line emission line width.

Speaker: 悠世 松村 (埼玉大学理工学研究科)

21 XRISM/Xtend Observation of X-ray Dimming Events on the Young Solar-type Star AB Doradus

Young solar-type stars produce frequent and energetic stellar flares. By solar analogy, such energetic stellar flares can drive coronal mass ejections (CMEs) and energetic particles, potentially affecting exoplanetary atmospheres. Although stellar CMEs are difficult to detect directly, extreme-ultraviolet and soft X-ray coronal mass-loss dimmings are often observed in solar CMEs and may provide a hint to stellar CMEs. Long-term soft X-ray monitorings are required to correctly evaluate the quiescent coronal emissions and to conclusively detect coronal dimming. We here conducted a nearly continuous five-day XRISM observation of the young solar-type star AB Doradus. Xtend covers the soft X-ray band even below 1.7 keV, which is suitable for detecting and characterizing the coronal dimming events. We detected 26 stellar flares and two dimming events with decreases of about 25%. The dimming origin could be rotational modulations, absorption by floating cool plasma, or CME-related dimming. The dimmings occurred at different rotational phases and are inconsistent with TESS's optical rotational modulation, making rotational modulation unlikely. In both dimmings, the count rate decreased nearly uniformly over 0.4-10 keV, indicating that X-ray absorption by floating cool plasma (prominences) is unlikely. Instead, the decrease in total emission measure strongly favors the scenario of CME-related mass-loss dimmings. Moreover, the observed EM decreases are consistent with the theoretical EM values of CME-related dimmings derived from the information of the preceding X-ray flares, further supporting the flare-driven CME scenario. We will discuss this interpretation and future dimming searches in active M dwarfs.

Speaker: Daijiro Hitotsuyanagi (Kyoto University)

4:00 PM Coffee break

Poster Presentation: (Block 2)

22 Distinct Velocity Components in the Absorption Lines of the Neutron Star X-ray Binary AX J1745.6–2901

Accretion disks in X-ray binaries regulate mass transfer onto compact objects and drive radiative and kinetic feedback to their surroundings. Here we report X-ray spectroscopy of the eclipsing neutron star low-mass X-ray binary AX J1745.6–2901 with XRISM/Resolve.
The phase-averaged Fe~XXVI Ly$\alpha$ absorption profile exhibits two absorption minima with relative depths that are inconsistent with the theoretical Ly$\alpha_1$/Ly$\alpha_2$ doublet ratio expected from a single velocity component. We demonstrate that this profile is well described by two discrete velocity components: a blueshifted component at $v \simeq -160 $km s$^{-1}$ and a redshifted component at $v \simeq +590 $km s$^{-1}$. The significance of the redshifted component is more than $3\sigma$ based on a Monte-Carlo calculation. This velocity structure persists across orbital phases, disfavoring a localized origin such as a bulge or dip. The blueshifted component, well below the outer-disk escape velocity, is consistent with a slow outflow or disk atmosphere. The redshifted absorber can be explained either by infalling gas from a failed wind or by a gravitational redshift, and the present data cannot rule out either possibility. Regardless of its origin, the redshifted component is kinematically separate from the disk atmosphere and outflow. The absence of absorption at intermediate velocities further indicates a genuinely bimodal velocity distribution rather than the two ends of a single continuous flow, offering a new view of the absorbing-gas kinematics.

Speaker: Kai Matsunaga

23 Multiwavelength Monitoring of Broad-Line Region Kinematics via the Fe Kα and Hβ Emission Lines in NGC 4151

The Fe Kα line probes the structure and kinematics of circumnuclear gas around supermassive black holes. XRISM observed NGC 4151 fourteen times between December 2023 and December 2024. XRISM Collaboration (2024) and Miller et al. (2026) showed that its Fe Kα profile contains multiple velocity components, with contributions from the broad-line region (BLR) and the dusty torus. We then conducted optical and near-infrared follow-up monitoring. Zhao et al. (submitted) suggested that the narrow Fe Kα component originates well beyond the inner wall of the dusty torus. Hirata et al. (submitted) found that broad Hβ exhibits a variable asymmetric profile consisting of a central peak and two shoulders.
We fitted the XRISM Fe Kα profiles using the three-Gaussian Hβ model of Hirata et al. plus an additional narrow component, and examined their temporal variability. The model reproduces the profiles well, suggesting that Fe Kα-emitting gas shares the velocity structure of the optical BLR. The additional narrow component has a nearly constant intensity and a velocity dispersion of approximately 200 km/s. Its narrow width indicates that this component originates well beyond the inner wall of the dusty torus, supporting Zhao et al. We propose continued coordinated XRISM, optical, and near-infrared monitoring. Densely sampled short-term observations can identify reverberating Hβ and Fe Kα velocity components, while monitoring over the coming decade will trace variability in the distant narrow component and connect BLR kinematics with the dusty torus.

Speaker: Guangyuan Zhao (Tokyo University of Science)

24 Orbital Phase-resolved Analysis of Fe K Emission Lines in the X-ray Binary 4U 1538-522 with XRISM

We present an XRISM/Resolve study of the eclipsing supergiant high-mass X-ray binary 4U$~$1538$-$522. The system consists of a neutron star and the B0.2 Ia supergiant QV Nor, and its nearly edge-on geometry makes it well suited for tracing fluorescent material through the orbital modulation of iron K-shell emission. XRISM observed the source for approximately 290 ks, covering about 90% of its 3.7-day orbit, with an effective exposure of about 187 ks. Using the high spectral resolution of Resolve, we divided the observation into eight orbital phases and fitted each spectrum with absorbed continuum and Fe K$\alpha$/K$\beta$ fluorescence-line models. A prominent Fe K$\alpha$ line was detected in all phases, and both its centroid energy and flux showed systematic orbital variations. From the energy separation between the Fe K$\beta$ and Fe K$\alpha$ lines during eclipse, we estimated an iron charge state of $q \approx 5$. Comparison with simple line-of-sight velocity models indicates that the fluorescent emission most likely originates on, or near, the companion-star surface. The phase-dependent Fe K$\alpha$ flux variation is also consistent with this interpretation. These results demonstrate the capability of XRISM/Resolve to simultaneously constrain the ionization state and emission site of fluorescent material using the resolved Fe K$\alpha$ and K$\beta$ lines. In future work, we will systematically apply this Fe K$\alpha$/K$\beta$ diagnostic to various X-ray binaries observed with XRISM to assess the universality of the inferred ionization states and emission sites.

Speaker: Keita Hasegawa (Kyoto University)

25 Probing Asymmetric Explosive Mass Ejection through Fe-K spectroscopy in Core-collapse Supernova Remnants with XRISM

Neutron-star kicks are thought to arise from asymmetric explosive mass ejection in core-collapse supernovae. X-ray studies have shown that intermediate-mass elements, such as Si and S, are preferentially expelled opposite to the direction of neutron-star motion in young supernova remnants, supporting a hydrodynamic origin of the kicks (Katsuda et al. 2018). Fe-rich ejecta, produced in the deepest layers, offer a more direct probe of explosion asymmetry, but their Fe-K emission is faint and difficult to map spatially and kinematically.
We present an XRISM program motivated by the first detection of extended Fe-K emission at ~6.5 keV from Puppis A with Resolve and Xtend. Resolve spectroscopy indicates a low-ionization Fe component, while Xtend imaging reveals localized Fe-K emission broadly associated with Si-rich ejecta. Combining two-dimensional Fe-K maps from Xtend with line-of-sight velocity and velocity-broadening constraints from Resolve will allow us to investigate the three-dimensional distribution and bulk motion of Fe-rich ejecta.
We will apply this approach to G292.0+1.8, G15.9+0.2 and N49. In G292.0+1.8, XRISM data suggest enhanced Fe-K emission in the northwest and southwest; Chandra found Si-, S-, and Fe-rich X-ray-emitting ejecta opposite to the pulsar’s projected displacement (Bhalerao et al. 2019). G15.9+0.2 is a promising XRISM target, with Fe-K line emission and a candidate central compact object reported from XMM-Newton and Chandra studies (Maggi & Acero 2017). Archival XRISM data for N49 will enable a comparative test of asymmetric explosive mass ejection using the innermost SN products.

Speaker: Jun Kurashima (University of Miyazaki)

26 Probing Cosmic-Ray Acceleration with XRISM/Resolve and Optical Shock-Velocity Measurements

Cosmic-ray acceleration is one of the long-standing unresolved problems in high-energy astrophysics. Galactic cosmic rays are widely considered to be accelerated at supernova-remnant shocks through diffusive shock acceleration. However, it remains unclear what physical conditions enable the efficient transfer of shock kinetic energy into non-thermal particles.
To investigate these conditions, it is essential to determine the post-shock energy partition. In the absence of efficient cosmic-ray acceleration, a substantial fraction of the shock kinetic energy is converted into ion thermal energy, resulting in high post-shock ion temperatures. If acceleration is efficient, part of this energy is transferred to non-thermal particles, reducing the downstream ion temperature. Comparing shock velocity with ion temperature is therefore a key diagnostic for assessing the efficiency of cosmic-ray acceleration.
XRISM/Resolve provides a unique opportunity to measure ion temperatures through the thermal broadening of X-ray emission lines. Complementing this, SDSS-LVM is a wide-field integral-field spectroscopic survey (35.3″ angular resolution) designed to map the ionized interstellar medium, enabling spatially resolved measurements of shock velocities and post-shock proton temperatures through Balmer-dominated Hα emission. Together, the shock velocity measured with SDSS-LVM and the ion temperature measured with XRISM/Resolve can constrain how shock kinetic energy is partitioned between thermal plasma and non-thermal particles.
In this talk, I will present an ongoing study of RCW 86 using existing NuSTAR observations and SDSS-LVM data covering the remnant. I will also discuss how XRISM/Resolve observations after gate-valve opening could measure ion temperatures in shocked plasma and constrain the efficiency of cosmic-ray acceleration.

Speaker: Gen Fujimoto (Tokyo University)

27 Probing the inner region of the AGN torus by combining XRISM/Resolve spectroscopy with dust reverberation mapping

Active galactic nuclei (AGNs) are a key population for understanding the evolution of supermassive black holes (SMBHs). Although the broad-line region (BLR) and dusty torus serve as gas reservoirs, their compact structures remain poorly constrained. With high energy resolution, XRISM/Resolve can decompose the Fe K$\alpha$ line into multiple velocity components. However, linking these velocity components to the inner edge of the torus and the BLR structures remains challenging, leaving their origins uncertain.

In this work, we locate the Fe K$\alpha$-emitting regions relative to the torus inner radius ($\mathrm{R_{dust}}$) by combining the XRISM/Resolve spectroscopy with the dust reverberation mapping method. First, we analyzed the spectra of NGC 4151 (type-1), MCG-5-23-16 (type-1.9), and NGC 4388 (type-2) to estimate the Fe K$\alpha$-emitting radii. The lines were modeled using the MYTorus line-emission table, which describes X-ray reprocessing in a toroidal geometry, convolved with Gaussian broadening for the broad ($\sigma=1000$--$3000$ km/s) and narrow ($\sigma=100$--$400$ km/s) components. We next measured $\mathrm{R_{dust}}$ by applying the X-ray and infrared dust reverberation mapping (Noda et al. 2020) to Swift/BAT and WISE archive data of these galaxies. This method determines $\mathrm{R_{dust}}$ from the infrared time lag relative to X-ray flux variations. As a result, we found that the broad-component radii are within $\mathrm{R_{dust}}$, supporting a BLR origin. In contrast, the narrow-component radii are typically several to over ten times larger than $\mathrm{R_{dust}}$, which is consistent with a torus origin. This suggests either a small solid angle of the torus inner edge or the presence of an obscuring structure shielding it.

Speaker: Yuya Sakamoto (Tohoku University)

28 Probing the Structure and Composition of the Relativistic Jets in SS 433 with XRISM

SS 433 is a unique Galactic microquasar undergoing persistent supercritical accretion and launching relativistic baryonic jets. Its X-ray spectrum exhibits highly ionized Doppler-shifted emission lines from precessing bipolar jets. We present the emission-line profiles and their variability revealed by XRISM observations conducted to date, providing new insights into the structure and composition of the relativistic jets. XRISM/Resolve spectroscopy has revealed that the Fe and Ni emission lines become broader as the jets emerge from eclipse by the companion star. This suggests that the jet velocity dispersion decreases with increasing distance from the compact object, consistent with progressive collimation or the decay of turbulence. We also find that the Ni/Fe abundance ratio in the jets is enhanced by a factor of ~6 relative to the solar value. In contrast, the Ni/Fe ratio inferred from the neutral fluorescent lines, which are likely produced in the accretion flow, is constrained to be <~2 times the solar value. This indicates that the jets are significantly more Ni-rich than the accreting material, possibly reflecting nucleosynthesis in the vicinity of the compact object. We will also discuss how future XRISM observations will further constrain the dynamical structure and chemical composition of the jets.

Speaker: Dr Toshihiro Takagi (Ehime University)

29 Sloshing Motions in Abell 3571 Revealed by XRISM/Resolve Velocity Mapping

Minor mergers can induce sloshing motions, leaving characteristic thermodynamic and kinematic signatures in cluster cores. A3571 is an X-ray-bright cluster at $z\sim0.04~(R_{500}=1.25~\mathrm{Mpc})$. Outside its central region, its thermodynamic structure resembles that of the Perseus cluster, despite the absence of a prominent cool core. We observed the central $\sim300~\mathrm{kpc}$ region of A3571 with six XRISM Resolve pointings, totaling $\sim700~\mathrm{ks}$. Velocity dispersions are subsonic at $\sim100\text{-}150~\mathrm{km~s^{-1}}$. The northern surface-brightness excess is blueshifted by $\sim60~\mathrm{km~s^{-1}}$ relative to the brightest cluster galaxy, while the southern and eastern deficits are redshifted by up to $\sim170~\mathrm{km~s^{-1}}$. Simulations suggest that the asymmetry is consistent with early-phase sloshing induced by an off-axis minor merger. Abell 3572, an X-ray-faint cluster $1.6~\mathrm{Mpc}$ south of A3571, is a plausible perturber. Without strong AGN feedback signatures, these results suggest that sloshing-driven gas redistribution may delay the formation of a strong cool core in A3571. We also compared line-of-sight velocity differences in A3571 with those in Perseus. Their smaller amplitudes indicate that gas motions in A3571 are dynamically quieter than in Perseus, despite the absence of a strong cool core.

Additional northern and southern observations, together with approved western observations, would provide nearly complete coverage of the projected sloshing structure. Such a mosaic would enable second-order velocity structure function measurements at separations up to $\sim600~\mathrm{kpc}$ and direct comparisons with numerical simulations. Such coverage would constrain the characteristic scales on which sloshing drives gas motions and provide new insight into how merger-induced motions develop across a cluster core.

Speaker: Mr Itsuki Aihara (Tokyo University of Science)

30 Spectroscopic exploration of Type I bursts with XRISM

Type I bursts are transient explosions triggered by the thermonuclear burning of the accreted matter accumulated on neutron star (NS) surfaces. The accreted fuels burn through the $\alpha$-capture process branching from the hot CNO cycle, subsequently triggering hydrogen burning such as rapid-proton capture ($rp$) process. While burst light curves or fluences serve as useful probes for these burning processes, the direct spectroscopic evidence has yet to be reported.

We report the discovery of multiple consecutive Type I bursts with nearly consistent recurrence time—so called "clocked bursts"—from Circinus X-1 (hereafter Cir X-1) using archival NuSTAR data. Through our analysis of the burst light curves and fluences, we have successfully proved that Cir X-1 is the hydrogen-rich binary where accreted matter burns explosively by the unique process. Furthermore, we suggest that Cir X-1 might exhibit multiple Type I bursts during the every orbital phase range of $\sim$0.2–0.7 (Ishii & Enoto et al. submitted to ApJ).

We propose that high-resolution spectroscopy of Cir X-1 around $\sim$0.2–0.7 orbital phase with XRISM could reveal more direct evidence of the hydrogen-burning process, such as absorption lines from heavier nuclei originating from burst ashes.

Speaker: Nonoka Ishii (Department of physics, Kyoto University)

31 The intermediate-mass elements ejecta kinematics study of Kepler’s SNR with XRISM/Resolve

Type Ia supernovae are explosive thermonuclear explosions in white dwarfs, and they play a important role in astrophysics, for example, as standard candles for measuring distances to distant objects. However, multiple scenarios have been proposed for the progenitor systems and explosion mechanisms of Type Ia supernovae, and many aspects remain unresolved. On the other hand, the velocity distribution of the ejecta in supernova remnants (SNRs) reflects the structure at the time of explosion, providing important clues to the progenitor systems and explosion mechanisms of individual SNRs.

Kepler's SNR is the remnant of the Galactic SN recorded in 1604, and its progenitor is thought to have undergone a Type Ia supernova explosion. In this study, we analyzed X-ray spectra emitted by intermediate-mass elements such as Si and S contained in the ejecta using XRISM/Resolve. For the spectrum of each region, we performed two-component fitting assuming redshifted and blueshifted components, and measured the Doppler velocities for each region. As a result, the Doppler velocities of the intermediate-mass-element ejecta showed a spherically symmetric velocity structure in both the redshifted and blueshifted components, in contrast to the asymmetric distribution of the Fe ejecta (Kasuga et al. 2018; 2026 Spring Meeting N25a Ichiseki, etc.). On the other hand, in the eastern region, we detected redshifted ejecta with a high velocity of $3400^{+420}_{-240}$ km/s that deviates from the spherically symmetric velocity structure. Based on these results, we will discuss the differences the between intermediate-mass elements and Fe ejecta, and the explosion structure.

Speaker: Osuke Akita (Saitama University)

32 XRISM Observation of Stellar Flares from Algol

Algol is a well-known eclipsing binary system consisting of a B-type primary and a magnetically active K-type secondary star. Owing to the strong coronal activity of the secondary, Algol is one of the brightest stellar X-ray sources. During stellar flares, coronal plasma is rapidly heated to temperatures exceeding $10^7$ K, making high-resolution X-ray spectroscopy a powerful tool for investigating the heating process, ionization state, and elemental composition of the plasma.

We observed Algol with the X-Ray Imaging and Spectroscopy Mission (XRISM) from 7 to 13 February 2026 and detected multiple stellar flares during the observation. In addition to the Fe K-shell lines, the He-like lines of Ca, S, and Ar were clearly detected, providing valuable diagnostics of the temperature structure and ionization balance of the hot flare plasma.

Among the detected events, the largest flare exhibited prominent Fe He$\alpha$ and Ly$\alpha$ emission lines. Because these lines are sensitive to the temperature and ionization state of the plasma, their temporal evolution provides important constraints on the heating and cooling processes during the flare. In this presentation, we will report an overview of the XRISM observations of Algol and the temporal behavior of the detected flares. We will then focus on the largest flare and discuss the temperature evolution of the hot plasma based on the intensities and intensity ratio of the Fe He$\alpha$ and Ly$\alpha$ lines.

Speaker: Kazuya Nakayama (Kyoto University)

Banquet

Tue, August 25

Science Talk: Extended emission and Emission mechanism

Convener: Prof. Kazuhiro Nakazawa (Nagoya University, KMI)

33 Constraining the Cosmic-Ray Contribution to Fe Kα Emission in the Sgr A Complex

The Fe K$\alpha$ emission from the Sgr A complex is mainly attributed to irradiation by past Sgr A$^\ast$ activity. On the other hand, low-energy cosmic rays may also produce steady Fe K$\alpha$ emission through inner-shell ionization. Indeed, previous radio observations have suggested a high ionization rate due to low-energy cosmic rays in the Galactic Center region.
The Fe K$\alpha_{3,4}$ satellite originates from a state with simultaneous K- and L-shell vacancies, and its intensity relative to the Fe K$\alpha_{1,2}$ main lines depends on the ionization process. Ground-calibration measurements provide the Fe K$\alpha_{3,4}$/K$\alpha_{1,2}$ ratio for X-ray irradiation, while particle-impact calculations predict that ion impacts enhance the ratio. Therefore, this intensity ratio can be used to constrain the relative contributions of X-ray irradiation and cosmic-ray ionization.
We observed the Sgr A complex with XRISM/Resolve and detected the Fe K$\alpha_{3,4}$ satellite on the high-energy side of the Fe K$\alpha_{1,2}$ lines. The measured Fe K$\alpha_{3,4}$/K$\alpha_{1,2}$ intensity ratio is 1.27$\pm$0.65%. Using ground-calibration data obtained by irradiating an iron target with X-rays, we derived a ratio of 0.92$\pm$0.32%. The present XRISM result is consistent with X-ray irradiation, but its uncertainty is too large to constrain an additional cosmic-ray contribution.
We therefore propose a deep XRISM reobservation of the Sgr A complex to measure the Fe K$\alpha_{3,4}$/K$\alpha_{1,2}$ ratio more precisely. Comparison with the ground-calibration measurement and particle-impact calculations will constrain the fraction of Fe K$\alpha$ emission produced by low-energy cosmic rays and provide a constraint on the low-energy cosmic-ray density in the molecular cloud.

Speaker: Yuma Aoki

XRISM_c2c_YumaAoki_en_v2.2_sharing.pdf

34 Investigation of Spatial Variations in the Highly Ionized Iron-Line Complex of the Galactic Center X-ray Emission with XRISM/Resolve

The origin of the Galactic Center X-ray Emission (GCXE) remains unclear. Although 10 – 40% of the GCXE has been resolved into detected point sources with Chandra, it is unknown whether the remaining emission originates solely from unresolved point sources or from truly diffuse plasma.
Using the XRISM/Resolve data, we resolved the fine structures of the Fe-Heα and Fe-Lyα lines and measured their intensities, Doppler shifts, and line widths. We investigated the plasma excitation and ionization states using the Fe-Heα G-ratio.
The G-ratio exhibits significant spatial variations, ranging from approximately 0.75 to 2.0, while the Fe-Lyα/Heα changes only slightly. Significant regional variations are also found in the Doppler shifts and line widths. If the GCXE were dominated by point sources, each Resolve field would contain more than ~1,000 sources, and these spectral properties would be expected to show only limited spatial variations owing to averaging. The observed variations therefore suggest the presence of an additional diffuse component.
To identify the origin of the unresolved GCXE component, it is essential to construct representative high-resolution spectral templates for the major X-ray point-source populations, to predict their Fe-line diagnostics quantitatively, and to compare them with the observed spatial variations in the GCXE. This requires XRISM observations of nearby active binaries and magnetic/non-magnetic cataclysmic variables, together with continued Resolve mapping of the Galactic center, enabling quantitative separation of the unresolved point-source and diffuse plasma components.

Speaker: Anje Yoshimoto (Nara Women's University)

35 Merger-driven ICM motions and energy dissipation revealed by XRISM/Resolve

Galaxy cluster mergers release enormous gravitational energy into the intracluster medium (ICM), driving bulk motions, shocks, turbulence, magnetic-field amplification, and particle acceleration. However, the connection between thermal-gas dynamics and diffuse radio emission remains poorly understood.

In this talk, I will present recent XRISM/Resolve results, focusing on Abell 3667. XRISM reveals a large line-of-sight velocity difference between the cluster center and the southeastern cold front, together with a velocity shear of approximately 570 km s$^{-1}$ across the front. These results indicate large-scale sloshing or rotational motions induced by an off-axis merger.

The velocity dispersion reaches about 440 km s$^{-1}$ immediately inside the cold front, decreases to approximately 0–150 km s$^{-1}$ at distances of 200–400 kpc, and then rises again to around 200 km s$^{-1}$ at 500–600 kpc. Comparison with the radio emission shows that the strongest line broadening does not coincide with the brightest radio-emitting region. Instead, the radio emission becomes brighter where the velocity dispersion increases again.

In contrast, Abell 2319 hosts bright central mini-halo emission despite showing similar sloshing or rotational gas motions. This may indicate a larger reservoir of fossil relativistic electrons or a longer time since the onset of sloshing. I will further discuss how the spatial evolution of turbulence, seed-electron populations, and magnetic-field structure jointly determine where and when merger-driven gas motions produce diffuse radio emission.

Speaker: Yuki Omiya (ISAS/JAXA)

Poster Presentation: (Block 3)

36 AGN Feedback and Gas Dynamics in M87, the Central Galaxy of the Virgo Cluster

Observational evidence for the long-predicted "cooling flow" in the cores of galaxy clusters has rarely been found, and AGN are considered the most promising heating source suppressing this cooling.Understanding this AGN feedback requires knowledge of the velocity structure of the intracluster medium (ICM), which is a key physical parameter. M87, the central galaxy of the Virgo Cluster, is an ideal target for this study: X-ray observations reveal large-scale substructures including the eastern and southwestern arms, bubbles, and shock fronts that suggest interaction between the AGN and ICM.To investigate in detail the gas motions driven by AGN feedback, we analyzed observational data of M87 obtained with Resolve onboard the XRISM. By dividing the Resolve field of view into multiple small regions and measuring the velocity in each, we identified a region 14 kpc southwest of M87 exhibiting gas motion blueshifted by approximately 110 km/s relative to M87.　This may represent the motion of hot gas uplifted by a bubble formed through AGN feedback.
In this poster, we present the spatial distribution of bulk velocity and velocity dispersion across all subregions and discuss the gas dynamics in M87.

Speaker: Daisuke Ito (Nagoya University)

37 Compton Shoulder Analysis of the Accretion-Powered Pulsar GX 301−2

GX 301$-$2 is a massive X-ray binary hosting a $\sim$700 s neutron star and a B-type supergiant companion on a highly eccentric ($e \sim 0.46$), $\sim$42-day orbit. Past Chandra observations detected a Compton shoulder on its strong Fe K$\alpha$ fluorescence line, indicating dense scattering material near the neutron star, but limited CCD spectral resolution left the line profile and physical state of the emitting region poorly constrained.

We present XRISM/Resolve observations of GX 301$-$2 (59 ks, February 1–3, 2025) covering the pre-periastron flare, when accretion increases. The high-resolution spectrum resolved a narrow ($\sim$3 eV) K$\alpha$ line from low-ionization iron together with a K$\beta$ line. An ionization-diagnostic method applied to their energy separation gives an average iron ionization degree of $\sim$4 at the emission site. Detailed modeling of the Fe K$\alpha$ line shape — performed with the Geant4-based Monte Carlo simulation tool MONACO, incorporating the line's fine structure — reconfirmed the known Compton shoulder and revealed an additional, broader component ($\sim$16 eV). The model further constrains the surrounding material's hydrogen column density ($\sim2\times10^{24}$ cm$^{-2}$) and metallicity ($\sim$0.5 $Z_\odot$), and points to a very low electron temperature, together indicating a cold, dense scattering medium around the neutron star.

This poster presents these Fe K-line ionization diagnostics and Compton shoulder results, along with orbital- and spin-phase-resolved variability analysis, to characterize the emitting region and discuss the accretion environment of GX 301$-$2.

Speaker: Yutaro Nagai (Kyoto University)

38 Efficient Collisionless Electron Heating in the Supernova Remnant RCW 86 Revealed with XRISM

Collisionless shocks in astrophysical plasmas, such as supernova remnants (SNRs), are ubiquitous phenomena. The electron-to-ion temperature ratio immediately behind the shock is expected to be as low as their mass ratio, $\beta \equiv kT_{\mathrm{e}}/kT_{i} = m_{\mathrm{e}}/m_{i}$ in the extreme collisionless limit. However, SNR observations have revealed significantly higher values of $\beta$, indicating the presence of rapid electron heating at the shock front. In the southwestern region of the SNR RCW 86, Fe fluorescence lines from low-ionized ejecta have been detected. This indicates the presence of immediately post-shock plasma, making this region an ideal site for investigating the imprint of collisionless electron heating. To constrain $\beta$, we performed high-resolution spectroscopy of Fe emission lines in this region with XRISM. The observed flux ratio of the Fe-K$\beta$ to K$\alpha$ lines is $0.092^{+0.032}_{-0.016}$. The line centroids were measured to be $6.393^{+0.002}_{-0.002}~\mathrm{keV}$ for K$\alpha$ and $7.094^{+0.012}_{-0.021}~\mathrm{keV}$ for K$\beta$. We compare the observed line flux ratio, centroids, and widths with those of theoretical calculations, constraining the redshift (bulk velocity), ionization state, shock velocity $V_\mathrm{sh}$, and initial temperature ratio $\beta$. The allowed parameter combinations of $V_\mathrm{sh}$ and $\beta$ span from $\beta = m_{\mathrm{e}}/m_{i} \sim 10^{-5}$ ($V_\mathrm{sh}\approx 5800~\mathrm{km~s^{-1}}$) to $\beta = 1.0$ ($V_\mathrm{sh}\approx9000~\mathrm{km~s^{-1}}$). Combined with the Fe K/L line flux ratio, the parameter sets with $\beta < 0.004 $ are disfavored, indicating efficient collisionless electron heating at the reverse shock front of RCW~86.

Speaker: Yoshizumi Okada (Aoyamagakuin university)

39 Exploring Galactic Soft X-ray Emission with the XRISM/Xtend Archive

The North Polar Spur (NPS), a bright X-ray and radio structure, has often been interpreted as the northern thermal limb of the eROSITA bubbles, attributed to an outflow from the Galactic Center. Using Suzaku observations, we found that the large-scale spatial distribution of Galactic soft X-ray emission can be described by three components: a Galactic halo, a disk-associated component, and a shell-like component whose brightest limb is traced by the NPS. We interpreted this shell as a nearby supernova remnant (Shimatani et al., submitted). Our spectral analysis indicated that the shell component can be described by an unabsorbed plasma with temperatures of approximately 0.3–0.5 keV, with possible signatures of nonequilibrium ionization in some regions.
The wide (38 x 38) arcmin field of view of XRISM/Xtend provides a major advantage for studies of diffuse Galactic X-ray emission. Even after excluding point sources and emission associated with primary observational targets, a substantial area often remains available for diffuse-emission analysis. This contrasts with Suzaku, whose smaller field of view can leave only a limited extraction area. Archival Xtend observations obtained for other purposes may therefore provide extensive and valuable coverage of Galactic diffuse emission. We compare Suzaku and Xtend observations of the same regions, evaluate the extraction areas available for diffuse-emission analysis, and examine the consistency of the resulting spectra. Based on these comparisons, we assess the feasibility and scientific potential of using the Xtend archive to investigate Galactic soft X-ray emission.

Speaker: Haruto Higuchi (Tokyo University of Science)

40 Modeling of Resonance-Scattered Fe Lines from Accretion Columns of Magnetic Cataclysmic Variables with a Unified Hydrodynamic and Radiative-Transfer Framework

Magnetic cataclysmic variables (MCVs) host a strongly magnetized white dwarf accreting gas from a companion star. The gas forms an accretion column with a standing shock near the magnetic poles. This column is the source of the X-ray emission.

Recent observations of AM Her with XRISM revealed a spin-phase dependence of the equivalent widths of the Fe XXV and Fe XXVI resonance lines (Terada et al. 2026). This demonstrates velocity and temperature gradients in the accretion-column plasma. It thus provides a new clue to constrain the physical parameters of the system.

For this purpose, we need to compute resonance scattering under such gradients, including the anisotropy of the scattering phase function. The goal of this study is to perform such calculations from first principles.

We first perform hydrodynamic calculations of the post-shock flow in the accretion column following Cropper et al. (1999), including gravity and multiple radiative cooling processes (bremsstrahlung, cyclotron, and line cooling). We derive the temperature, density, and velocity profiles of the post-shock region.

We then perform radiative-transfer calculations using the resulting accretion-column profiles. Resonance scattering is computed with a Monte Carlo method, and X-ray spectra are synthesized for various viewing angles. The calculation also includes the Doppler energy shift in each scattering (frequency redistribution), the scattering phase function, and linear polarization effects.

We discuss how the line ratios and their spin-phase dependence vary with the physical parameters of the system. We also compare them with the observed data and examine whether the physical parameters can be constrained.

Speaker: Momo Hayashi (TUS)

41 Modeling X-Ray Spectra from Clumpy Ultra-Fast Outflows with Three-Dimensional Monte Carlo Radiative Transfer Calculations

PDS 456 is an extraordinary quasar hosting a super-Eddington accreting Active Galactic Nucleus (AGN). Its extreme accretion activity and powerful relativistic winds make it an ideal object for investigating AGN feedback and the physical mechanisms of mass ejection from supermassive black holes.

The X-ray observation satellite XRISM, launched in 2023, has an energy resolution approximately ten times higher than that of conventional satellites. XRISM observations of PDS 456 revealed a clumpy Ultra-Fast Outflow (UFO) structure composed of five distinct velocity components (XRISM Collaboration, 2025). However, conventional one-dimensional (1D) radiative transfer calculations cannot incorporate clumpy structures, making it impossible to accurately derive detailed geometric properties from the observational data.

In this study, we construct a spectral model of the clumpy UFO based on the XRISM observational results using the three-dimensional Monte Carlo radiative transfer code MONACO (Odaka et al., 2011). We distribute 100,000 clumps with a diameter of 10 Rg within a hemispherical region at 400–600 Rg from the black hole and assign bulk velocities of 0.226–0.333c, following the XRISM-derived parameters. Our simulations successfully reproduce the observed five-component absorption-line structure and the broad emission-line feature.

We further investigate the effect of clumpiness by comparing the clumpy model with a non-clumpy outflow model while matching the average column density. The clumpy model shows weaker emission-line flux than the non-clumpy model, mainly due to the reduced effective column density. In this presentation, we discuss results in this study and compare them with previous 1D calculations.

Speaker: Kazuki Fujikawa (東京大学　理学系研究科)

42 Numerical studies of the contamination of the solar flare events on XRISM Xtend using Geant4

Accurate characterization and subtraction of background components in X-ray energy spectra are crucial for reliably detecting faint signals from astrophysical sources. During XRISM observation of M81 conducted between May 8 and 12, 2024, strong solar flares of up to X5.8 class occurred. The background spectrum observed by Xtend during this period shows an enhancement of the continuum X-ray component synchronized with the solar flares, and scattered components which may originate from satellite structures (Ishi et al. in prep. , Kobayashi et al. in prep.). In this study, we use Geant4, a Monte Carlo toolkit for simulating the interactions of particles (e.g., photons and protons) with the materials (e.g., spacecraft structures and detectors), to reproduce the observed background spectrum. The incident solar X-ray spectrum used in the simulations was estimated based on the X-ray flux observed by the GOES satellite. The mass model adopted for the simulations is based on the Hitomi mass model, which was constructed in Yasudaʼs master thesis at Saitama-University. We computed the direction of the incident solar X-rays relative to the satellite using the orbital and attitude information from this observation. As a result, we numerically confirmed that the observed continuous spectrum and Fe XXV emission lines can be successfully reproduced if solar X-rays are assumed to undergo single scattering by the X-ray mirror assembly (XMA) before being detected by Xtend. This result indicates that singly scattered solar X-rays constitute a major component of the flare-induced background in XRISM/Xtend data.

Speaker: Yuta Tsuchihashi (埼玉大学)

43 Probing the Geometry and Launching Mechanism of Ultra-fast Outflows through X-ray Variability

Ultra-fast outflows (UFOs) are highly ionized accretion-disk winds in active galactic nuclei. A major unresolved question is how these outflows are accelerated. Proposed mechanisms include large-scale magnetic fields, radiation pressure, and magnetic reconnection.
We investigate PDS 456 using a 500 ks simultaneous XRISM and NuSTAR observation. Broadband X-ray spectra reveal soft X-ray absorption produced by a low-ionization (logξ~ 3), partially covering UFO moving at ~0.3 c. Its covering fraction increased from ~0.88 to ~0.93. Interpreting this variability as the transverse motion of a clump yields a crossing velocity of ~$5\times 10^{-3}\,c$ and, assuming angular momentum conservation, a distance exceeding ~4000 gravitational radii. In contrast, the highly ionized Fe-K UFO detected by XRISM originates at ~200–600 gravitational radii with a similar outflow velocity. These results imply that the low- and high-ionization components occupy different radii despite similar velocities. This geometry constrains the UFO launching mechanism by disfavoring acceleration by large-scale magnetic fields, leaving radiation pressure and magnetic reconnection as the viable scenarios.
We therefore discuss how long-duration XRISM observations could distinguish between these remaining scenarios. The multiple velocity components of the Fe-K UFO suggest a clumpy structure. Measuring the transverse motion of individual clumps would determine their relative radial ordering and, together with their measured line-of-sight velocities, enable reconstruction of the velocity-distance relation within the outflow. Furthermore, detecting temporal changes in their line-of-sight velocities would directly measure their acceleration. These observations would test UFO launching mechanisms in PDS 456 and other AGNs with clumpy winds, including PG 1211+143 and IRAS 05189-2524.

Speaker: Riki Sato (The University of Tokyo)

44 Revealing the Accretion and Reflection Environment Close to the White Dwarf in T CrB with XRISM/Resolve

T CrB is a symbiotic recurrent nova comprising a white dwarf (WD) and a red giant, with outbursts recorded in 1886 and 1946. Recent optical monitoring shows a decline after years in a high-luminosity state, similar to its pre-eruption behavior, suggesting another outburst in the near future. X-ray spectroscopy probes accretion flows and reflecting material near the WD. The origin of the 6.4 keV fluorescent Fe K$\alpha$ line remains unclear, with the accretion disk, WD surface, and companion wind proposed. Because the line width reflects the line-of-sight velocity dispersion, high-resolution spectroscopy can distinguish emitting sites.

We present XRISM/Resolve spectroscopy of T CrB observed in July 2024 in an optical fading phase similar to those before previous outbursts. From Fe K$\alpha$ line-width measurements, we identify for the first time two fluorescent components with distinct velocity dispersions, $\sigma_v \sim 300$ and $\sim 2000~{\rm km~s^{-1}}$, unresolved by previous observations. The narrow component is most naturally explained by emission from the WD surface, rather than the companion wind or accretion disk. The broad component has a velocity dispersion comparable to that of the hot boundary-layer plasma, suggesting an origin in low-ionization material co-rotating with the plasma or in the inner accretion disk. Thus, Fe K$\alpha$ emission in T CrB arises from multiple sites around the WD. Together with planned XRISM observations during the next outburst, this pre-eruption circum-WD material distribution provides a crucial initial condition for interpreting the eruption evolution and tracing the system from pre- to post-eruption.

Speaker: Yugo Motogami (Saitama university)

45 Spectroscopic diagnostics of photoionized plasma in Vela X-1

High-mass X-ray binaries (HMXBs) consist of a neutron star or black hole and a companion star with a mass $\gtrsim10M_\odot$. Vela X-1 is a prototypical HMXB with a high inclination angle ($\gtrsim73^\circ$; e.g., van Kerkwijk et al., 1995), where the line-of-sight accretion structure varies with the orbital phase. In this work, we aim to investigate the spatial structures of photoionized plasma and cold matters with high-resolution X-ray spectroscopy with XRISM. The XRISM observations of Vela X-1 were conducted during the Commissioning phase, Performance Verification (PV) phase, and Announcement of Opportunity Cycle 1 (AO1), covering orbital phases $\varphi\simeq0.68-0.90$ , $0.25-0.29$, and $0.38-0.52$, respectively. During the PV and AO1 observations, a hardness ratio transition was observed. In addition, the Resolve detected low- and highly ionized Fe emission/absorption lines and Fe K edge from the Commissioning and AO1 data, while only low- and highly ionized Fe emission lines from the PV data. The R ratio, the intensity ratio between the forbidden and the intercombination lines, depends on the electron density and local UV photon flux. At $\varphi\sim0.49$ and $\varphi\sim0.70$, the R ratio was $0.54$ and $0.58$, respectively. However, at $\varphi\sim0.28$, the R ratio was $1.2$, significantly higher than other orbital phases. This phase dependence indicates that the emission region at $\varphi\sim0.28$ has a lower ionization parameter, suggesting a higher electron density or a larger distance from the neutron star. As a future prospect, observing other orbital phases will allow us to investigate different parts of the accretion structure.

Speaker: Keigo Okabe (Aoyama Gakuin University / ISAS)

46 Velocity Structure of Intermediate-Mass Elements in the Type Ia Supernova Remnant 3C 397 with XRISM/Resolve

Type Ia supernovae (SNe Ia) are thermonuclear explosions of white dwarfs and major producers of silicon, sulfur, and iron, yet how they explode remains unresolved. Probing the velocity distribution of a supernova remnant (SNR) is key to constraining its explosion mechanism and surrounding environment.

3C 397 is one of the most promising candidates for the explosion of a white dwarf close to the Chandrasekhar limit, based on its iron-group abundance ratios (Yamaguchi et al. 2015, Ohshiro et al. 2021). Its X-ray image is remarkably asymmetric and boxy, but whether this originates from the explosion itself or from the circumstellar/interstellar medium is unclear. The key is the ejecta velocity structure, unresolvable with conventional detectors; the ~5 eV resolution of XRISM/Resolve now makes such measurements possible. We focus on intermediate-mass elements (IMEs; Si, S), whose high ionization and simple line structures make them ideal for Doppler measurements.

We mapped Doppler velocities and velocity dispersions of IMEs in the southeast of 3C 397. The easternmost region is redshifted by ~190 km/s and shows a velocity dispersion of ~670 km/s, significantly larger than the other regions. This suggests that the ejecta in this region are directed away from us.

We report these results and discuss the asymmetric expansion. XRISM now enables such measurements for many Type Ia SNRs. We will apply this method to those already observed and propose new observations. Analyzing multiple Type Ia SNRs will systematically separate explosion-induced from environment-induced asymmetries, addressing the long-standing problem of the SN Ia explosion mechanism.

Speaker: Naoya Ogura (The university of Tokyo)

11:00 AM Coffee break

Poster Presentation: (Block 4)

47 Approaching the Geometric Structure of 4U 1630-472 with Cooperative Observations by XRISM Spectroscopy and XL-Calibur Polarimetry

The low-mass X-ray binary GX340+0 is an extremely bright source near the Eddington limit. We analyzed data from the Resolve detector aboard the XRISM satellite. To eliminate the effect of dust scattering, we extracted data exclusively from the central 16 pixels. Because the source is highly luminous and the statistics when using only High-res data were insufficient, we applied a novel analysis approach that incorporates Mid-res data, thereby doubling the statistics. By comparing the spectra among the different states, we successfully detected state-dependent variations in the behavior of the Fe emission lines.
In this presentation, we propose a Cooperative observations targeting the outburst phase of the black hole X-ray binary 4U 1630-472, in collaboration with the hard X-ray polarimetry balloon mission, XL-Calibur. A previous XRISM observation of this source revealed a dramatic variation in absorption line depths between the Steady and Dip states, presenting a mystery that cannot be explained by current geometric models (Miller et al. 2025). To address this, we aim to determine the geometric structure of the accretion disk and disk wind through XL-Calibur's polarimetric observations, which directly probe the environment surrounding the source, while simultaneously conducting a spectroscopic analysis utilizing Resolve's Mid-res data. This synergistic approach will allow us to elucidate how geometric changes drive the spectral differences observed between the Steady and Dip states. Regarding the XRISM observation, we propose extending the exposure time from the previous ~50 ksec, and ideally, conducting either a simultaneous observation or a　coordinated observation close in time with XL-Calibur.

Speaker: Mr Masaki Maekawa (Hiroshima University)

48 Exploring the Structure and Dynamics of the SS 433 Jets with Simultaneous X-ray and Optical Spectroscopy

We present the results of simultaneous X-ray and optical spectroscopic observations of the microquasar SS 433 with XRISM/Resolve and the Seimei Telescope in 2024 and 2025. The X-ray jet emission lines exhibit single-peaked profiles, whereas the optical H$\alpha$ jet lines show one to three distinct components that form and decay on timescales of one to a few days. This contrast suggests that the optical-emitting plasma is more inhomogeneous and fragmented into discrete blobs. The evolution of the Halpha profiles is consistent with intermittent blob formation followed by outward propagation through the optical-emitting region. We also find that the velocity dispersions of the optical components (500-1000 km s$^{-1}$) are significantly smaller than those of the X-ray lines from the hotter inner jet ($\sim$ 2000 km s$^{-1}$), but comparable to those of the cooler outer X-ray-emitting region ($\sim$ 1000 km s$^{-1}$), suggesting a close physical connection between these regions. In addition, while the Doppler shifts of the receding (red) jet in 2024 largely follow the standard precession/nutation model, the approaching (blue) jet shows rapid deviations, indicating an asymmetric jet structure during the observation.Finally, we discuss how these results motivate future observations of SS 433 at different precession phases and the further insights they are expected to provide into the jet structure and dynamics.

Speaker: 宇宿 智哉 (愛媛大学)

49 Kinematically Resolving the Fe K Complex in Her X-1: Accretion Disk and Ionized Wind Across Eclipses

Viewed nearly edge-on, Hercules X-1 undergoes deep X-ray eclipses that act as a natural coronagraph: with the bright continuum blocked, only the reprocessed emission from the accretion disk and disk wind remains. We present XRISM/Resolve spectroscopy of three eclipses of Her X-1 taken in September 2024. The $\sim$5 eV resolution cleanly separates the iron K complex into neutral fluorescence (Fe K$\alpha$, K$\beta$) and highly ionized emission (Fe XXV He$\alpha$, Fe XXVI Ly$\alpha$) and tracks each through ingress, mid-eclipse, and egress. The neutral Fe K$\alpha$ line vanishes at mid-eclipse, indicating a compact origin; it is redshifted at ingress and blueshifted at egress, and the residual $\sim$180 km s$^{-1}$ shift implies Keplerian rotation at $\sim$$7\times10^{6}$ km, placing part of the fluorescence in the outer disk. The highly ionized lines persist through eclipse, tracing an extended photoionized plasma whose ionization and column density match the disk wind seen in absorption outside eclipse; an eclipse flux ratio diagnostic constrains the wind's inner launching radius to $\sim$$3\times10^{10}$ cm, consistent with a Compton-heated thermal wind. Looking ahead, the same eclipse-resolved, velocity-resolved Fe K method can be applied to other disk-accreting eclipsing binaries such as SMC X-1 and LMC X-4, testing whether the disk wind and reprocessing geometry found in Her X-1 is common among precessing disk systems and establishing eclipse spectroscopy as a general probe of accretion disk structure.

Speaker: Koh Sakamoto (Kyoto university)

50 Observation of Iron Emission Lines from GT Muscae with XRISM

Low-ionization Fe $K\alpha$ emission has been detected from RS CVn-type stars during large flares. Its origin has often been attributed to fluorescence following photoionization of photospheric iron by hard X-rays from flare loops, although a contribution from non-thermal particles cannot be ruled out. During quiescence, however, the low-ionization Fe $K\alpha$ emission is weak, and only a few observations have been reported. Thus the line intensity, temporal variability, and origin of the low-ionization Fe $K\alpha$ across both quiescent and flaring states remain insufficiently constrained. In this study, we analyzed XRISM observations of the RS CVn-type binary GT Mus obtained during quiescence. We detected a low-ionization Fe $K\alpha$ line at a significance of $7.0\sigma$, with a centroid energy of $6.404 \pm 0.001$ keV. The spectrum was well described by a two-temperature CIE plasma model. We also performed time-resolved spectroscopy and found that the plasma temperatures increased with time, followed by an increase in the hardness ratio. On the other hand, no significant temporal variation was detected in the centroid energy and intensity of the low-ionization Fe $K\alpha$ line. In the intervals with the highest hardness ratio, we found an excess in the $6.6$–$6.62$ keV band on the low-energy side of the Fe XXV He$\alpha$ complex. This excess may originate from Fe XXIV satellite lines. These results provide new diagnostics of coronal activity and the production mechanism of low-ionization Fe $K\alpha$ emission in quiescent RS CVn-type stars. We present the details of the spectral and time-resolved analyses, together with plans for future observations.

Speaker: Masaru Kato (Kindai University)

51 Probing Gas Motions in the Cool-Core Cluster Abell 2199 with XRISM/Resolve

XRISM observed the central $100\times100$ kpc region of the nearby cool-core
cluster Abell 2199 (z=0.03). It revealed that the intracluster medium (ICM) redshift is consistent with that of the brightest cluster galaxy, within the optical-redshift uncertainty. This indicates that they form a kinematically coherent core system, which offset from the mean cluster redshift by $\sim200~\mathrm{km~s^{-1}}$. The observed velocity dispersion of $\sim100~\mathrm{km~s^{-1}}$ corresponds to a three-dimensional Mach number of $\mathcal{M}_{\mathrm{3D}}=0.16$ and a non-thermal pressure fraction of $P_{\mathrm{NT}}/P_{\mathrm{tot}}=1.4\pm0.2\%$. Abell~2199 is one of the most dynamically quiescent relaxed clusters observed with XRISM, despite the presence of radio jets and a plume-like structure possibly associated with sloshing motions. Order-of-magnitude estimates suggest that turbulent dissipation could offset a non-negligible fraction of the radiative cooling losses, with $Q_{\mathrm{turb}}/Q_{\mathrm{cool}}\approx0.2$ for a large-scale driver such as sloshing and larger values for smaller AGN-feedback scales. Finally, we detect a localized enhancement of the Fe XXV He$\alpha$ $y$ line in the SE region, which spatially coincides with a Chandra surface brightness discontinuity.
We propose three additional XRISM/Resolve pointings to test the sloshing scenario suggested by the SE surface-brightness jump and SW plume, and to investigate the line anomaly. The proposed eastern pointing will cover the SE edge and its exterior, enabling direct measurement of velocity shear expected across a sloshing cold front, and testing the connection of the $y$ line excess to the edge. The SW pointing will trace gas motion along the plume, while the NW pointing will provide a reference for the large-scale velocity field.

Speaker: Kazunori Suda (Tokyo University of Science)

52 Probing the Dynamic Emission Mechanisms of Time-Variable Neutron Stars via Xtend Wide-Field Serendipity

Xtend’s wide 38'×38' field of view (FoV) serendipitously captures other time-variable sources present during primary target observations. During AO1 N63A observations, the high-mass X-ray binary pulsar LMC X-4 serendipitously entered the FoV. While past studies of its 30-day superorbital modulation yielded only fragmented snapshots, we achieved unprecedented, continuous 8-day monitoring during a high-to-low state transition.
Spectral fitting of the power-law continuum up to 10 keV revealed the photon index varying from Γ=0.6 down to -0.3, confirming the dynamic progress of accretion disk occultation. Simultaneously, we modeled the 6.4 keV neutral iron fluorescence line to diagnose the reprocessing matter.
We further evaluate the statistical probability of capturing binary pulsars or magnetars during random pointings inside a 60°×2° galactic region, finding a high probability of ~30% per individual pointing. This enables unveiling the geometrical structure of disk modulation through continuous pulsar luminosity variations and performing highly accurate determination of magnetar luminosity decays post-outburst.

Speaker: Hiroumi Matsuhashi (The university of Tokyo)

53 Probing the Spatial Structure of Ejecta in Cassiopeia A with Line Diagnostics

Supernova explosions drive the material circulation and structural evolution of galaxies by supplying heavy elements and injecting kinetic energy. Investigating the plasma states of supernova remnants and their ambient interactions is crucial to understanding explosion mechanisms and post-explosion asymmetries. Cassiopeia A (Cas A), a young corecollapse supernova remnant, provides an ideal laboratory for this.We analyzed the silicon (Si) and sulfur (S) emission lines in Cas A using high-resolution spectroscopic data from XRISM/Resolve. We successfully separated two distinct plasma components with significantly different velocity dispersions in the northwestern region. The velocity dispersions of the broad and narrow components were $\sim 2000\text{ km s}^{-1}$ and $\sim 500\text{ km s}^{-1}$, respectively. The narrow component, detected for the first time owing to Resolve's superb resolution, suggests localized plasma structures such as clumpy ejecta or shocked filaments. Furthermore, the forbidden to resonance line intensity ratios of the He$\alpha$ lines for the narrow component were $\sim 0.6$ for Si and $\sim 0.5$ for S. These are significantly higher than expected in a typical thermal plasma ($\sim 0.3$ for both), indicating that standard non-equilibrium ionization models cannot reproduce the observed spectra. This anomaly suggests additional physical processes, namely resonance scattering and charge exchange. Driven by this discovery, XRISM conducted follow-up observations of the southwestern region of Cas A in May 2026. We report detailed spectral analysis including these new data and discuss their physical implications.We will also discuss prospects for reconstruction of the spatial structure of supernova ejecta based on spectral diagnostics.

Speaker: Tomohiro Suzumura (The University of Tokyo, ISAS/JAXA)

54 Revealing the Matter Distribution around Active Galactic Nuclei with XRISM and ALMA

Understanding the distribution and kinematics of matter around active galactic nuclei (AGNs) is essential for elucidating how mass accretes onto central supermassive black holes. The neutral Fe Kα line in AGN X-ray spectra often shows both a broad component with velocity widths of several thousand km/s and a narrow component with widths of several hundred km/s, as increasingly revealed by the high energy resolution of the Resolve microcalorimeter aboard XRISM. The narrow component is thought to originate in the torus, yet its physical and kinematic connection to molecular gas in the more extended circumnuclear disk remains unclear. This study combines high-resolution X-ray spectroscopy with millimeter molecular line observations to quantitatively constrain the matter distribution around AGN from sub-pc to 100 pc scales. We analyze nine AGNs observed by XRISM for which high-resolution ALMA CO(J=2-1) data resolve the central 100 pc. From the XRISM data, we precisely measure the velocity width of the narrow Fe Kα component. From the ALMA data, we derive the CO line velocity width, gas spatial distribution, and torus inclination angle, using the latter to constrain the inclination-independent emission radius of the Fe Kα line. We compare this radius with the black hole mass and AGN X-ray luminosity to investigate correlations with the surrounding matter distribution, and directly compare the velocity widths of the Fe Kα and CO lines to assess the spatial relation between their emitting regions. We will present our results to date and discuss future prospects.

Speaker: Aiko Miyamoto (The University of Osaka)

55 The Kinematics of Substructures in Type Ia SNRs Revealed by XRISM

Type Ia supernovae are one of the key sites of iron-group element production, yet their explosion mechanisms and progenitors remain unresolved. In young Type Ia supernova remnants (SNRs), localized structures such as ejecta knots preserve imprints of the explosion and its environment. Their abundances, kinematics, and ionization states have stimulated diverse discussions on explosion models, progenitor systems, and the origins of these structures (e.g., Yamaguchi et al. 2017; Sun & Chen 2019). XRISM/Resolve now enables simultaneous measurements of Doppler velocities, line widths, and ionization timescales for such structures.
Kepler's SNR, one of the youngest Galactic Type Ia SNRs, is an ideal target, with strong Fe-K emission and measurable ejecta kinematics. Although asymmetric ejecta have been reported (Kasuga et al. 2018), they have not yet provided specific constraints on the explosion model.
We present a XRISM/Resolve analysis of its Fe-K emission, modeling the centroid, width, and ionization timescale in the central and northern regions. The central region is dominated by a redshifted component, indicating a line-of-sight asymmetry in the ejecta distribution or its interaction with the ambient medium. The northern region requires a fast redshifted component and a nearly unshifted component, the latter likely decelerated by the circumstellar medium. The fast component is difficult to explain by circumstellar inhomogeneity alone, suggesting an intrinsic explosion asymmetry. We discuss how combining these measurements with elemental abundances can reveal the nucleosynthetic origin and formation history of such structures, thereby constraining Type Ia explosion models, and explore its application to other Type Ia SNRs.

Speaker: Iroha Ichiseki (The University of Tokyo)

56 XRISM Constraints on the Abundance Ratios of P, Cl, and K in W49B

High-resolution X-ray spectroscopy with XRISM has opened a new window on odd-Z nucleosynthesis by enabling the detection of emission lines from odd-Z elements such as P, Cl, and K, whose cosmic origins have remained largely unconstrained. To date, however, secure detections of these elements have been limited to the young Galactic supernova remnant Cassiopeia A. Extending such measurements to other supernova remnants is therefore essential for understanding the origin of odd-Z elements and their role in Galactic chemical evolution.
We investigate the nucleosynthetic yields of the Galactic supernova remnant W49B using XRISM/Resolve observations. W49B is one of the brightest supernova remnants observed by XRISM, and its high X-ray flux and intrinsically narrow emission lines make it an ideal target for high-precision abundance measurements. Moreover, its explosion mechanism and progenitor remain under debate, making odd-Z elemental abundances a potentially powerful new diagnostic of its origin.
We measure the abundance ratios of odd-Z elements relative to even-Z elements, including K/Ar, and find that these ratios are systematically sub-solar. These results disfavor progenitor scenarios involving extremely high metallicity or shell-merger models. By comparing the observed abundance pattern with some nucleosynthesis models , we derive new constraints on the progenitor of W49B. Our results suggest that high-resolution measurements of odd-Z elements with XRISM provide a powerful new diagnostic of supernova nucleosynthesis and progenitor scenarios.

Speaker: Koki Negishi (Meiji University)

12:00 PM Group Photo

12:15 PM Lunch Break

Invited Lecture

Convener: Hiroya Yamaguchi (ISAS/JAXA)

57 From EBIT measurements to XRISM spectra: atomic data for high-resolution X-ray diagnostics

High-resolution spectra from XRISM Resolve open a new window on astrophysical plasmas, but their diagnostic power depends critically on the accuracy of atomic data. In this lecture, I will introduce how laboratory measurements with electron beam ion traps (EBITs) provide benchmark data for interpreting X-ray spectra, including line ratios, ionization balance, and velocity diagnostics. I will highlight recent results on electron-impact excitation and dielectronic recombination for K- and L-shell ions, as well as precision wavelength and oscillator strength measurements enabled by combining EBITs with synchrotron and free-electron-laser light sources. I will focus on how these data improve spectral models used in XRISM analysis, reduce systematic uncertainties in X-ray plasma diagnostics, strengthen the interpretation of XRISM spectra, and help design future observation strategies.

Speaker: Chintan Shah (NASA Goddard Space Flight Center)

58 Non-Thermal Pressure in Galaxy Clusters, from Cosmological Simulations to XRISM

Hot gas in galaxy clusters is often modeled as sitting in simple hydrostatic equilibrium, but real clusters are dynamically alive: turbulence and bulk flows left over from mergers and accretion provide additional, "non-thermal" pressure support that has long been a major uncertainty in cluster astrophysics and cosmology, simply because it could not be directly measured. XRISM's Resolve instrument has changed that, providing the first high-resolution X-ray spectroscopic measurements of gas velocities in cluster cores.In this lecture I will use cosmological hydrodynamical simulations to foward model what non-thermal pressure looks like in a realistic cluster population — how it depends on a cluster's cool-core state and assembly history — and then walk through how we connect these simulations to real XRISM data by generating synthetic XRISM/Resolve observations of simulated clusters exactly as the telescope would see them, so that projection effects and spectral-fitting systematics can be disentangled from genuine cluster physics before any comparison to real data is made.
I will present our recent forward-modeling results compared to XRISM observation of Abell 2029, whose measured non-thermal pressure sits at or below the lowest few percent of the simulated cool-core cluster population, even after fully accounting for viewing-angle and projection effects. I will use this result to introduce some of the open questions currently facing the field in the XRISM era.

Speaker: Erwin Lau (Nara Women's University)

3:30 PM Coffee break

Invited Lecture

Convener: Kyoko Matsushita (Tokyo University of Science)

59 NewAthena and the AGN astrophysics: exploring the (hot and) energetic Universe

This talk briefly traces the historical path that led to ESA’s NewAthena flagship mission for X-ray astronomy, framing its design within the broader development of high-energy astrophysics. After a swift look at this evolution, I will outline the major technical challenges involved in designing an observatory capable of addressing the astronomical community's fundamental questions. I will then highlight recent spectroscopic breakthroughs from XRISM that are redefining our understanding of active galactic nuclei (AGN) environments. Finally, I will showcase how NewAthena’s advanced instrumental capabilities will probe accretion, ejection mechanisms, and supermassive black hole growth across cosmic time.

Speaker: Prof. Mauro Dadina (INAF)

Award / Closing

Convener: Dr Yukikatsu Terada (Saitama University / JAXA)