MAXI 15 Year Workshop for the Time Domain Astronomy

10 Dec 2024, 10:00 → 12 Dec 2024, 16:00 Asia/Tokyo

CST Hall (in Bld. A in the map) (Nihon university)

MAXI 15 Year Workshop for the Time Domain Astronomy

Caution: Some travel companies are sending e-mails to the participants in the name of the MAXI workshop. However, MAXI workshop DOES NOT participate any travel companies. 

Program is open. Visit "Timetable" tab. Click each talk for abstract.

We are happy to announce to hold 
the MAXI 15 Year Workshop for the Time Domain Astronomy 
on December 10-12, 2024, at Nihon university, Tokyo Japan

to celebrate the 15 years of successful operation of MAXI, or Monitor of All-sky X-ray Image, an X-ray all-sky monitor onboard the Japanese Experiment Module of the International Space Station. 

   The registration for presentation and visa documents were closed. We have 119 attendance. 46 of them are from abroad.

We still welcome listening only (no presentation and no banquet) participants. Please make a registration through the registration page. 

 

In 1997, we organized the First MAXI Workshop at RIKEN entitled "All-Sky X-ray Observations of the Next Decade". From then, it took more than a decade for MAXI to start observing on orbit.Two decades later, time-domain astronomy is playing in the central arena of studies in the physics of the Universe, with MAXI watching the variable X-ray sky since August 15, 2009.

Currently, wide-sky discovery engines, like Swift, Fermi, EP and MAXI, provide the astrophysical transients to follow.  Ground based facilities, such as ZTF and ATLAS, are also finding cornucopia of new sources to explore, augmented by recent additions of observatories for non-electromagnetic messengers, namely, gravitational waves and neutrinos.

For follow-up observations of these transients, telescopes with flexible scheduling capabilities are becoming more important.  In space, telescopes on Swift, NuSTAR, NICER, and HXMT have been aggressively following transients. Automatic follow-up system on ISS, OHMAN, has been functioning. Small satellites such as GECAM and cubesats such as NinjaSat have been taking their unique roles. On the ground, small to medium sized telescopes such as GOTO are found to be very useful for these studies.  Big observatories, both ground- or space-based, remain important in cases where sensitivities or high resolution are essential. Ground large quick telescope such as VLT/X-shooter, and GTC/ORISIS+ are very effective. Chandra with high positional resolution, XRISM with high energy resolution and IXPE and Polix with polarimeters are on orbit. 

MAXI has been uniformly scanning the entire sky for the 15 years, and has been regularly reporting the discoveries to Astronomers Telegram and GCN; detections of outbursts of new or previously known X-ray sources including discoveries of 14 new galactic black holes binaries such as MAXI J1535-571, and MAXI J1820+070, a hundred of gamma-ray bursts, tens of giant stellar flares, and a couple of very rare phenomena, namely the relativistic tidal disruption event Swift J1644+57 and ultra luminous soft X-ray nova MAXI J0158-744.  The accumulated scan data are processed to generate the 3MAXI catalogs of X-ray sources with 896 entries.

In this workshop, we hope to review the scientific results triggered by the MAXI observations.  The topics include physics of high energy astrophysical sources, their emission, accretion, and outflow processes, in particular, those of black holes, neutron stars, and active stars.  We also hope that this workshop will facilitate new research collaborations for the coming decade between theorists and observers at all wavelengths.

Tatehiro Mihara (RIKEN) and Hitoshi Negoro (Nihon-u)
on behalf of the MAXI 15 year workshop organizers

http://maxi.riken.jp/conf/15year

Invited speakers :
Jamie Kennea (Swift, USA)  
Sean Pike (NuSTAR, USA)  
Lian Tao (HXMT, China)
Roger Romani (IXPE, USA)
Weimin Yuan (Einstein Probe, China)
Erik Kuulkers (INTEGRAL, ESA)
Bishwajit Paul (Polix, India)
Jean-Luc Atteia (SVOM, France)
Makoto Tashiro (XRISM, JAXA)
Anna Ho (ZTF, USA)
Megumi Shidatsu (MAXI transients, Ehime-u)
Chris Done (BH binary, UK)
Alexandra Tetarenko (Radio, Canada)
Stephane Corbel (Relativistic jets, France)
David Russel (BH binary, UAE)
Kevin Alabarta (XB-NEWS, UAE)
Tomokage Yoneyama (XRISM transients, Chuo-u)
Tomoshi Takeda (NinjaSat, Riken)
Wataru Iwakiri (NICER, Chiba-u)

 

Scientific Organizing Committee :
Hitoshi Negoro (Nihon-u), Tatehiro Mihara (RIKEN), Megumi Shidatsu (Ehime-u),
Motoko Serino (Aoyama-u), Mutsumi Sugizaki (Kanazawa-u), Motoki Nakajima (Nihon-u),
Wataru Iwakiri (Chiba-u), Yoko Tsuboi (Chuo-u), Satoshi Sugita (Aoyama-u), 
Ken Ebisawa (JAXA/ISAS), Yoshihiro Ueda (Kyoto-u), Nobuyuki Kawai (RIKEN)

 

This workshop is sponsored by Japan Tourism Agency "promotion of international conferences in university".

Tuesday 10 December

10:25 → 10:30 Opening remark

Negoro

10:30 → 12:00 10-1

Chair: N. Kawai (RIKEN)

10:30 MAXI status and recent results

MAXI has been working for 15 years and contributing to a part of the time-domain astronomy by the quick alerts of transients. The main instrument GSC of MAXI has been stable after some damage occurred in the first year. The other instrument SSC has damaged due to the radiation damage. The main system of the MAXI suffered abrupt shut down twice in 2022 June. Since then SSC was stopped to reduce the load of the power supply. MAXI discovered 35 sources in 15 years, including 14 black hole binaries. Since the previous 7 yr workshop, bright X-ray novae appeared, such as MAXI J1535-571, MAXI J1820+070, MAXI J1631-479, MAXI J1348-630, MAXI J1803-298, and 4U 1543-475. Two Be X-ray binary pulsars were discovered in the anti-galactic center direction, as MAXI J0709-159 and MAXI J0655-013.

Speaker: Tatehiro Mihara (RIKEN MAXI team)

10:50 MAXI transients in 15 years

MAXI discovered 35 newly discovered X-ray novae or short transients, including 14 or more black hole candidates and the first Be/whit-dwarf nova MAXI J0158-744. The nature of some of them are still unknown. MAXI also detected a number of X-ray novae and X-ray or gamma bursts. I briefly summarize those transients sources MAXI discoverd/detected in 15 years.

Speaker: Hitoshi Negoro (Nihon University)

11:10 Swift and MAXI: 15 Years of Collaboration

The Neil Gehrels Swift Observatory, which turns 20 years old in November 2024, is an epochal mission for TDAMM science thanks to it's rapid response capabilities, allowing for fast turn around observation of transients both discovered by Swift itself, and other observatories. It's combination of sensitive X-ray and UV/Optical telescopes allows for broadband follow-up of events discovered by MAXI and others. Before MAXI launched, it was recognized that Swift and MAXI are strongly complementary missions, and the two teams agreed to collaborate on transient discovery. This began a 15 year long collaboration between the two teams in which transients discovered by MAXI were regularly observed by Swift in order to accurately localize, categorize and follow-up these new events, which has resulted in ~100 publications on joint results from Swift and MAXI. In this talk I give a history of this collaboration and talk about selected scientific about highlights of this collaboration, including most recently the co-detection of GRB 221009A, AKA "The BOAT", the brightest Gamma-Ray burst ever seen and observations of GW events by Swift and MAXI. Finally I talk about the future of the collaboration, demonstrating new capabilities that Swift plans to bring online in the next 12 months which can further complement MAXI's discovery potential.

Speaker: Jamie Kennea (Penn State)

11:40 NuSTAR and MAXI: capturing transient sources near the Sun

MAXI provides all-sky monitoring in the X-ray band, identifying multiple new sources each year, but a fraction of these transient sources falls too close to the Sun for most X-ray observatories to safely perform rapid follow-up observations. NuSTAR, however, is able to observe sources with much smaller angular separation from the Sun than other observatories, making it a uniquely capable tool for capturing X-ray transient data that would otherwise go unobserved. I will present recent results which have been achieved by performing rapid NuSTAR follow-up of X-ray transients discovered near the Sun by MAXI, including measurements of the spin and inclination of a faint black hole X-ray binary, and hints at an anomalously high magnetic field in a slow-spinning neutron star Be X-ray binary. I will also discuss the analysis challenges that come with observing near the Sun with NuSTAR, as well as the importance of monitoring newly discovered X-ray sources at multiple stages of their evolving outbursts.

Speaker: Sean Pike (UC, San Diego)

12:00 → 13:30 Lunch

13:30 → 15:00 10-2

Chair: T. Mihara (RIKEN)

13:30 Status and preliminary results of Einstein Probe

The Einstein Probe (EP) is a space X-ray observatory designed to detect mainly high-energy transient and variable sources in the universe. It aims at detecting such sources at unprecedented sensitivity and spatial resolution in the soft X-ray band and performing quick onboard follow-up observations in X-rays. The Einstein Probe is a project led by the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. EP was launched on January 9, 2024. Till July, the satellite has completed the commissioning and in-orbit calibrations. Since then, EP has started the nominal science operations. This talk will introduce the mission status, the instrument performance and preliminary science results of the transient and variable sources detected.

Speaker: Weimin Yuan (National Astronomical Observatories, Chinese Academy of Sciences)

14:05 Transient search and multi-wavelength identification for the Einstein Probe mission

Eintein Probe (EP) is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability, and was lauched on January 9, 2024. It carried out a series of performance verification and calibration observation after launch and had begun scientific observations since late July. By now, EP has detected more than 30 fast X-ray transients, and long-term transients of different origin. Of which, some are very puzzling transients and their nature are still under investigation. In this talk, we will introduce the strategy we adopt to search for the transeints. For short term transients, like GRBs and stellar flares, that show high amplitude varibility during one single exposure, the Bayesian block algotithm is adopted to search for the variability signal. While for long-term, and relatively fainter transients, like TDEs, data stacking is used to increase the detection sensitivity. All these sources have been carefully identified following a series of cross-matches with astronomical data bases and multiwavelength catalogues, and also follow-up observations. In this talk, we will give a brief intriduction to the transient search and source identifications for EP, and also priliminary results of some peculiar EP transients.

Speaker: Dongyue Li (National Astronomical Observatories, CAS)

14:25 Development and Operation Status of X-Ray Imaging and Spectroscopy Mission (XRISM)

The X-Ray Imaging and Spectroscopy Mission (XRISM) project was initiated in 2018. Following the development of onboard components, the proto-flight was conducted from 2021 to 2023 at JAXA Tsukuba Space Center. The spacecraft was launched from JAXA Tanegashima Space Center on September 7, 2023, and onboard components, including the observation instruments, were activated during the four months of the in-orbit commissioning phase. From February, the planned performance verification observations were conducted until the end of August, and the guest observations selected by JAXA, NASA, and ESA started in September. In this paper, we show initial results obtained in the performance verification phase, not only by the precise X-ray spectroscopy by the onboard X-ray micro-calorimeter but also by the wide field of view X-ray CCD camera.

Speaker: Makoto Tashiro (Saitama univ)

15:00 → 15:20 break

15:20 → 16:40 10-3

Chair: W. Iwakiri (Chiba Univ.)

15:20 XRISM/Xtend Transient Search: Deep X-ray Transients

X-ray Imaging and Spectroscopy Mission (XRISM) has two X-ray instruments. Resolve, an X-ray microcalorimeter, has an extreme energy resolution of 5 eV at 6 keV. Xtend, an X-ray CCD array, has a large field of view (FoV) of 38 arcmin square, which gives us opportunities to observe many serendipitous sources. We developed the XRISM/Xtend Transient Search (XTS), a project to quick search and fast report for X-ray transient detected by Xtend. XTS has ~ 3 orders of magnitude higher sensitivity than that of MAXI (with limited FoV). XTS is the first attempt to make the fast reports for transient sources with a pointing satellite (i.e., non-survey type mission). XTS started on Mar. 2024. We have reported 17 transients via the Astronomer's Telegram (ATel) so far (2024-09-30). Most of them are stellar flares with X-ray fluxes of 10^-13 -- 10^-11 erg/s/cm^2. In this presentation, we report the development, operation and results during the "performance verification phase" of XRISM by Sep. 2024.

Speaker: Tomokage Yoneyama (Chuo University)

15:50 Followup and monitoring observations of MAXI flare stars in optical bands

Since MAXI's launch in 2009, we have continuously surveyed stellar flares. The flare sample now exceeds 200 and has been found to originate from about 30 active stars, including RS CVn systems, Algol systems, dMe stars, dKe stars, YSOs, and undefined-type stars. The observed parameters of these MAXI flares are: luminosity of 10^31-10^34 erg s-1 in the 2-20 keV band, emission of 10^54-10^57 cm-3, temperature of 1-16 keV, e-folding time of 6-360 ksec, radiation energy during the decay phase of 10^34-10^39 erg. These parameters indicate the upper limit of the stellar flare. The radiation energies are orders of magnitudes greater than the largest flares occurred at the Sun - the solar flare has a maximum of 10^32 erg. These differences raise the question of how such huge amounts of magnetic energy are stored and where these events originate. One of the keys to understanding this question may be multi-wavelength observations, since the flaring plasma will be essentially multi-temperature. With this idea, we have installed three optical telescopes on the rooftop of a building at Chuo University Korakuen campus, which is called CHAO (CHuo-university Astronomical Observatory). CAT (Chuo-university Astronomical Telescope) and SCAT (Spectroscopic Chuo-university Astronomical Telescope) have been executing photometry and low-dispersion spectroscopy, respectively, and PHAST (Photometric And Spectroscopic Telescope) can simultaneously perform photometry and high-dispersion spectroscopy, with very fast tracking capability for transient detected with MAXI at a world-class driving speed of 20 degrees per second. Despite that the Korakuen campus is located at a downtown Tokyo in Japan and the diameters of the three telescopes are just in the range of 26-41 cm, we have been accumulating good examples of the flares from MAXI stars. We will review the dynamics, the situation at the flare onset, and e-folding time, obtained with CHAO and the other large telescopes at the followup and monitoring observations of MAXI flare stars.

Speaker: Yohko Tsuboi (Chuo University)

16:20 X-ray study of non-thermal plasma in stellar flares triggered by MAXI

We detected a giant X-ray flare from the RS-CVn type binary star UX Ari using MAXI on 2020 August 17 and started a series of NICER observations 89 minutes later. For a week, the entire duration of the flare was covered with 32 snapshot observations including the rising phase. The X-ray luminosity reached 2$\times$10$^{33}$~erg~s$^{-1}$ and the entire energy release was $\sim 10^{38}$~erg in the 0.5--8.0~keV band. X-ray spectra characterized by continuum emission with lines of FeXXV He$\alpha$ and FeXXVI Ly$\alpha$ were obtained. We found that the temperature peaks before that of the flux, which suggests that the period of plasma formation in the magnetic flare loop was captured. Using the continuum information (temperature, flux, and their delay time), we estimated the flare loop size to be $\sim 3 \times 10^{11}$~cm and the peak electron density to be $\sim 4\times10^{10}$~cm$^{-3}$. Furthermore, using the line ratio of FeXXV and FeXXVI, we investigated any potential indications of deviation from collisional ionization equilibrium (CIE). The X-ray spectra were consistent with CIE plasma throughout the flare, but the possibility of an ionizing plasma away from CIE was not rejected in the flux rising phase. In this talk, we also discuss the XRISM observation strategy for stellar flares using MAXI.

Speaker: Miki Kurihara (UTokyo, ISAS)

16:40 → 17:00 break

17:00 → 18:25 10-4

Chair: T. Tamagawa (RIKEN)

17:00 X-ray Polarization in the Variable Sky

The Imaging X-ray Polarimeter Explorer (IXPE) has opened up a new window on the X-ray sky, with observations of nearly 100 sources. In this talk I summarize IXPE's technical advances, the challenges of polarization measurements, our successes to date and the prospects for future discovery. IXPE has obtained polarization images of a number of X-ray nebulae, including pulsar wind nebulae and supernova remnants, that are probing the particle acceleration mechanisms. IXPE is also acquiring polarized light curves and spectra of accreting neutron star and black hole systems, in various outburst and quiescent states. These results provide new insights into the neutron star surface magnetization, black hole binary disk/corona structure and the particle energization in blazar jets. Polarization measurements require high photon counts and, with IXPE's modest aperture, MAXI alerts to transients and enhanced flux states of these highly variable sources have been integral to the mission's success.

Speaker: Roger Romani (Stanford University)

17:30 MAXI and NICER collaboration for soft X-ray transients

MAXI provides us with a powerful tool for detecting soft X-ray transients, such as outbursts of LMXBs or HMXBs, long-duration X-ray bursts, and stellar flares. To investigate more detailed physical processes of these X-ray transients, it is important to obtain the precision timing and spectroscopy data by rapid follow-up observations with high-sensitivity X-ray detectors. The Neutron Star Interior Composition Explorer (NICER), which was installed on ISS in June 2017, has the capability of rapid response to the newly reported MAXI transients and high-sensitivity X-ray timing and spectral observations. Moreover, NICER enables short high cadence observations of these transients. We report on the results of successful collaboration between the MAXI and NICER teams so far.

Speaker: Wataru Iwakiri (Chiba University)

17:50 Finding Relativistic Stellar Explosions as Fast Optical Transients

For the last half-century, relativistic outflows accompanying the final collapse of massive stars have predominantly been detected via high-energy emission, as long-duration gamma-ray bursts (GRBs). Yet, it has long been hypothesized that GRBs are the tip of the iceberg of relativistic stellar explosions, because the conditions required to produce and detect a GRB are contrived. I will present results from a search for relativistic stellar explosions using optical time-domain surveys. The emerging zoo includes afterglows at cosmological distances with no detected GRB, supernovae with luminous X-ray and radio emission, and a mysterious class of "fast blue optical transients" with minute-timescale optical flares at supernova-like luminosities. An understanding of the origin of these events and their relation to GRBs will be enabled by upcoming time-domain surveys in other bands, including X-ray, UV, and submillimeter.

Speaker: Anna Ho (Cornell University)

Wednesday 11 December

09:00 → 10:20 11-1

Chair: M. Sugizaki (Kanazawa U.)

09:00 INTEGRAL contributions to time domain astronomy

This presentation will review the main, unique, contributions of the INTErnational Gamma-Ray Astrophysics Laboratory, INTEGRAL, to time domain astronomy.

Speaker: Erik Kuulkers (ESA)

09:30 Orbital phase resolved and Intensity resolved spectroscopy of HMXBs with MAXI

Orbital phase-resolved spectroscopy of High Mass X-ray Binaries (HMXBs) allow detailed probe of the X-ray reprocessing environment and line of sight absorption of the X-rays by the stellar wind through different lines of sights in the binary. Same study, when carried out at different intensity levels of a given binary system allows probes of the changes in the reprocessing/absorption agents which may also be responsible for the X-ray intensity variations. We have investigated several HMXBs, including GX 301-2, Cen X-3, and Vela X-1 for their orbital phase dependence of the spectral parameters and intensity dependence of the same using long term data from MAXI-GSC onboard the ISS. Insights gained from the MAXI results for these individual systems to understand their stellar wind characteristics will be presented.

Speaker: Biswajit Paul (Raman Research Institute)

09:50 A new mechanism for state transition in Be X-ray binaries

Be X-ray binaries (BeXRBs) consist of a Be star (a massive star with a circumstellar disk) and a neutron star. They constitute a prominent subclass within the category of high-mass X-ray binaries, characterized by their transient nature. These binaries intermittently exhibit X-ray outbursts, whereas the rest of the time they remain quiescent. On the transition between these two X-ray activity states, it is believed that a BeXRB enters a quiescent state when accretion onto the neutron star is impeded by its rapidly rotating magnetosphere. However, the observational support for this centrifugal inhibition of accretion, often referred to as the propeller mechanism, comes only from a couple of systems with a neutron star with a relatively short spin period. The applicability of this mechanism in other BeXRBs, particularly those housing slowly rotating neutron stars, remains uncertain. In this presentation, we explore a possibility that in misaligned BeXRBs, the wind of the Be star can strongly suppress accretion, dispersing the accreting gas by its large ram pressure. Employing analytical models for both the wind and accretion disk, we compare the wind ram pressure with the gas pressures of the accretion flow for a number of systems with well determined/constrained parameters. We find that in some systems the state transition from the X-ray outburst to the quiescence is likely attributed to the inhibition of accretion by the stellar wind. In order to better understand how this mechanism works, we discuss the interaction between the stellar wind and the accretion flow in more detail, on the basis of the results from 3D hydrodynamic simulations.

Speaker: Atsuo Okazaki (Hokkai-Gakuen University)

10:05 Novel Paradigms of Magnetars Opened by Advanced Timing Studies

Advanced timing studies of archival data from ASCA, Suzaku, NuSTAR, and XMM-Newton are opening several novel aspects of magnetars. (1a) Representative 7 magnetars were found to be axially deformed to 10^{-4}, and performs free precession. (1b) The deformation is due to internal magnetic pressure, with the internal (toroidal) magnetic fields reaching 10^{16} G (Makishima+24a, 24b). (2a) The toroidal (Bt) to dipole (Bd) magnetic-field ratios of the 7 magnetars increase towards older objects; their Bt lasts longer than their Bd (Makishima+24a). (2b) Considering the Bd decay, magnetars could dominate new-born neutron stars (Nakano+15). (2d) There may be a large population of old magnetars with weak Bd but strong Bt. (2e) The very long periods (e.g., 6.7 hours) of some Central Compact Objects in supernova remnants are not their rotational periods, but are the slip periods of their free precession. Their true rotation period may reside at about 1 second. (3a) Magnetars are also found in binaries, such as X-Persei (via MAXI observations; Yatabe+18) and the gamma-ray binary LS 5039 (Yoneda+20, Makishima+23). (3b) As in LS 5039, magnetars can steadily accelerate particles up to TeV energies, probably via induced electric fields. (3c) The magnetars in binaries allow first measurements of the mass of magnetars. As indicated by X-Persei and LS 5039, magnetars could have a higher mass (~2.0 Msun) than the ordinary neutron stars.

Speaker: Kazuo Makishima (The University of Tokyo and RIKEN)

10:20 → 10:40 break

10:40 → 12:00 11-2

Chair: M. Nakajima (Nihon-u)

10:40 Overview of the Scientific Results from the Insight-HXMT Space Mission over 7 Years in Orbit

The Insight-HXMT space mission is China's first X-ray astronomical satellite, which has been in orbit for over 7 years. Its main scientific objectives include searching and monitoring transients in the disk of the Milky Way, observing X-ray binaries to study the motion and radiation mechanisms in strong gravitational or magnetic fields, and monitoring and studying gamma-ray bursts and electromagnetic counterparts of gravitational waves. Insight-HXMT has achieved a number of important results in these research areas. In this report, I will present the most important results and discuss the potential for collaboration with time-domain astronomical satellites such as MAXI.

Speaker: Lian Tao (Institute of High Energy Physics, Chinese Academy of Sciences)

11:10 MAXI X-ray monitoring of transient high-mass X-ray binary pulsars

We report on the results of MAXI monitoring of X-ray binary pulsars (XBPs), which are mostly high-mass X-ray binaries hosted by Be stars or OB supergiants. So far, about a hundred of XBPs have been known in our Galaxy. More than a half of them appear as X-ray transients whose activity are limited within their short (< several months) outburst periods. The MAXI all-sky survey for 15 years discovered several new XBPs including MAXI J1409-619, MAXI J0903-531, and MAXI J0655-013, and revealed their comprehensive outburst behaviours. Be XBPs usually exhibit outbursts lasting a few weeks to several months, according to the mass accretion on to a neutron star from a Be circumstellar disk. We investigated correlations between X-ray intensity variations observed by MAXI/GSC and pulse-period changes observed be Fermi/GBM for all clearly detected Be-XBP outbursts, and found that all of them reasonably agree with those predicted by theoretical models about the mass accretion along the pulsar magnetosphere. The model-fit results suggest that some Be XBPs with a long pulse period, X Persei, MAXI J0655-013, and LS V +44 17 would have strong magnetic fields of > 10^13 G, higher than the typical ~10^12 G. On the other hand, that of the ultra-luminous X-ray pulsar, Swift J0243.6+6124 was estimated to be typical ~10^12 G. We also examined the validity of these model predictions by comparing the results of all (~15) Be-XBP sample.

Speaker: Mutsumi Sugizaki (Kanazawa University)

11:30 Monitoring SMC X-1's Spin and Superorbital Modulation using MAXI and NinjaSat

SMC X-1 is a high-mass X-ray binary exhibiting superorbital modulation with an unstable period. Monitoring carried out by RXTE/ASM, Swift/BAT, and MAXI revealed excursion events in 1996–1998, 2005–2007, and 2014–2016, during which the superorbital period drifted from ~60 days to ~40 days. These events occurred at intervals of about 3,200 days. However, recent observations suggest that a new excursion occurred in 2020–2021, and the overall superorbital period shows a long-term decreasing trend. We further trace the spin-period evolution of SMC X-1 using MAXI and find that the spin-up rate accelerated one year before the onset of this new excursion, suggesting a possible inside-out process connecting the spin-up acceleration and the superorbital excursion. Further analysis of the pulse profile evolution reveals that the pulsed fraction exhibits long-term changes that may be connected to the superorbital excursion. These discoveries deepen the mystery of SMC X-1, as they cannot be solely interpreted by the warped-disc model. In 2024, we carried out a series of NinjaSat observations monitoring the spin frequency evolution. This regular monitoring reveals detailed spin-period evolution within a single superorbital cycle and may enhance our understanding of the underlying accretion mechanisms.

Speaker: Chin-Ping Hu (National Changhua University of Education)

11:45 Dust scattering echo around MAXI J1421-613 observed by Suzaku and Swift follow-up observations

MAXI J1421-613 is an X-ray burster discovered by MAXI on 9 January 2014 and is considered to be a low-mass X-ray binary. We report the discovery of an annular emission around MAXI J1421-613 in Suzaku and Swift follow-up observations. The Swift follow-up observation which was conducted by the photon counting mode on 18 January 2014 found an annular emission at ?2.5'--4.5' whereas the Suzaku observation on 31 January to 3 February 2014 detected an annular emission of 3'--9' radius around the transient source. The spectra of the annular emission were represented by an absorbed power law, and the photon index was higher than that of MAXI J1421–613 itself by delta Gamma ~ 2. The flux and radius of the annular emission observed by Suzaku and Swift are well explained by dust scattering of the same outburst of the transient. We estimate the distance to MAXI J1421-613 to be ~3 kpc assuming that the dust layer is at the same location as the CO cloud in front of MAXI J1421-613.

Speaker: Kumiko Nobukawa (Kindai University)

12:00 → 13:40 conference photo & Lunch

13:40 → 15:10 11-3

Chair: H. Negoro (Nihon-u)

13:40 MAXI detections and follow-up observations of outbursts from X-ray binaries

Since the start of the operation in 2009, MAXI has detected many outbursts from newly discovered and known Galactic black hole and neutron star X-ray binaries. They were promptly reported to the astronomical community over the world, which stimulated follow-up observations at various wavelengths. MAXI itself also provided unique long-term X-ray data covering their entire outburst periods, which gave us the overall picture of the spectral evolution during outbursts. In this talk, we showcase the MAXI detections and long-term monitoring of X-ray binaries and present the results of follow-up observations that we conducted with other observatories.

Speaker: Megumi Shidatsu (Ehime University)

14:10 The puzzling black hole candidate MAXI J1810-222

The X-ray transient MAXI J1810-222 was discovered by MAXI in 2018 and has been active ever since. A long, combined radio and X-ray monitoring campaign was performed with ATCA and Swift, respectively. It gas been identified as a black hole candidate, even though the highly unusual outburst behaviour and the absence of information regarding the distance or the donor leaves the nature of the compact object open to ongoing debate. We detected a strong spectral absorption feature at ~1 keV with NICER which was described with a physical photoionization model. Through a deep scan of the parameters space, we found evidence for a spectral-state dependent outflow, with mildly relativistic speeds at 0.05-0.15 c. This finding would make MAXI J1810-222 the first X-ray binary where ultra-fast outflows have been detected at such high speeds. This is unlikely from classical thermal winds in Galactic X-ray binary and must involve either strong radiation or (most likely) a magnetically-driven wind. Motivated by this findings, we obtained a high quality XMM-Newton observation in 2023, in order to deeply investigate the nature of this absorption feature. I will present preliminary results of this observation.

Speaker: Melania Del Santo (INAF/IASF Palermo)

14:25 Exploring the broadband spectral and timing characteristics of GRS 1915+105 with AstroSat and NICER

In this study, we undertake a spectral-timing analysis of the black hole X-ray binary source GRS 1915+105 using simultaneous observations carried out by AstroSat and NICER. The source showed two flux levels (high and low), whose energy spectra can be described by the thermal comptonization of disk photons. The spectral parameters obtained by the joint fitting of SXT/LAXPC and NICER/LAXPC were consistent. The power density spectra from LAXPC and NICER revealed a broad, prominent feature at ~2 Hz. The energy dependence of the fractional r.m.s and time lag of this feature cannot be explained by only variations of coronal spectral parameters. Instead, a model where the coronal heating rate varies first and induces a change in the disk temperature and inner radius can explain the variation.

Speaker: Ruchika Dhaka (Indian Institute of Technology Kanpur)

14:40 Relativistic jets and MAXI sources

Since the launch of MAXI 15 years ago, several considerable achievements have been reached in the field of Galactic accreting binary systems, especially in light of the extreme variability of their relativistic jets. These jets have now been recognized as vital component for energy transfer and angular momentum in black holes. Although the phenomenology is now rather well established, their emission and contribution to the total energy budget and the connection to the accretion disk are still the subject of active debates. In this review, I will present the most relevant observations concerning our understanding of relativistic jets in accreting systems and their coupling to the accretion disk, discussing in particular the key sources discovered by MAXI.

Speaker: Stéphane Corbel (Univ. Paris Cité / CEA Saclay / Observatoire de Paris)

15:10 → 15:30 break

15:30 → 16:35 11-4

Chair: C. Done (university of Durham)

15:30 Optical and X-ray monitoring of the early rise of the black hole X-ray binary, Swift J1753.5-0127

Despite decades of research, predicting outbursts of X-ray transients, and witnessing their beginning stages, remains very challenging. The cause of these X-ray brightenings is thought to be the sudden increase of accretion of matter onto a black hole or neutron star, initiated by the ionization of hydrogen in the accretion disc. I present recent observational advances in our understanding of how X-ray transients first brighten, focussing on the best case, optical and X-ray monitoring of the early rise of the black hole X-ray binary, Swift J1753.5-0127 in 2023. A delay of ~4 days is measured between a thermal instability developing in the accretion disc, causing heating fronts to begin propagating through the disc (seen by an optical brightening), and the onset of accretion onto the black hole (X-ray brightening). We witness the propagation of the heating wave, as a steady increase in the flux and surface area of the disc, and we constrain the disc viscosity. I demonstrate the ability of optical monitoring to be able to provide a few days (sometimes weeks) lead time to the rise of X-ray transient outbursts. This can help to inform X-ray missions, including possibly reducing the time needed to spot new outbursts in MAXI data.

Speaker: David Russell (New York University Abu Dhabi (NYUAD))

16:00 You snooze, you lose: catching the early rise of outbursts in LMXBs with XB-NEWS

Usually, X-ray binary (XRB) outbursts are first detected by X-ray all-sky monitors like MAXI. Only after this are observations with more sensitive multi-wavelength telescopes triggered. This causes a gap in the coverage of the rise of the outbursts, limiting our knowledge of their early stages. Therefore, the best approach to better understand the accretion process in XRBs is to combine X-ray observations with regular optical band monitoring. According to the disc-instability model (DIM), XRBs experience an earlier optical brightening than in X-rays at the beginning of the outburst. In this talk, we show that, with our regular monitoring of ~50 XRBs with the Faulkes Telescopes/Las Cumbres Observatory (LCO), we are detecting the optical brightening of XRBs typically ~11 days before the outbursts are detected in X-rays with MAXI. In addition, we show that outbursts rise at shorter optical wavelengths before rising at longer wavelengths. This seems to occur as the ionizing heating wave propagates through the disk at the onset of the outburst. In addition, we present our real-time data analysis pipeline, the "X-ray Binary New Early Warning System” (XB-NEWS), which we use to detect and announce new XRB outbursts within days of their first optical detection. This allows the community to trigger multi-wavelength campaigns at the very beginning of outbursts, constraining the physical mechanisms triggering them.

Speaker: Kevin Alabarta (New York University Abu Dhabi (NYUAD))

16:20 The delayed radio emission in the black hole X-ray binary MAXI J1348−630

Multi-wavelength observations are essential to understand the coupling between the accretion flow and the jet in black hole X-ray binary (BHXRB). We investigate the X-ray and radio emissions in MAXI J1348-630 during its 2019 outburst. For the first time, we find that the radio emission lags behind the X-ray Comptonization emission by about 3 days during the rising phase covering the rising hard state and the following soft state. Such a long radio delay indicates that, in this source, the Comptonization emission most likely originates from the advection-dominated accretion flow (ADAF) rather than the jet during the rising phase. Further, we study the correlation between the X-ray Comptonization and radio emissions in a broad X-ray energy band 0.1-100 keV. During the rising phase, considering the radio delay of ~ 3 days, we obtain a slope β = 3.04 ± 0.93, which is much steeper than the previously reported β = 0.6 or 1.40 using the total luminosity in the limited band (e.g., 1-10 keV). During the mini-outburst, the radio-Compton correlation becomes shallow with the correlation slope β = 1.11±0.15. These indicate an intrinsic difference in the accretion-jet coupling physics between the main outburst and the mini-outburst.

Speaker: Shuaikang Yang (Wuhan University)

16:35 → 16:55 break

16:55 → 17:45 11-5

Chair: J. Kennea (Penn State)

16:55 The radio view of MAXI transients

The most powerful cosmic engines in our universe are fueled by compact objects such as black holes and neutron stars. These cosmic engines accrete large amounts of material and eject matter in the form of jets traveling at near the speed of light. Recent groundbreaking discoveries of gravitational waves from systems harbouring compact objects and the direct imaging of the black hole shadows with the Event Horizon Telescope, represent major steps forward in our understanding of such systems. However, there exists a huge population of stellar-mass compact objects in our own Galaxy, present in transient X-ray binaries, which provide much more ideal laboratories by providing a real-time view of the behaviour of these objects and their dynamic environments. In this talk, I will review the key role that MAXI has played in identifying these explosive galactic transients, highlighting how we can leverage radio observations of these systems to track the path of material from inflow to outflow and gain unique insights into the accretion/jet ejection process.

Speaker: Alexandra Tetarenko (University of Lethbridge)

17:25 Geometrical and dynamic evolution of the accretion flow during the 2018 outburst of MAXI J1820+070

A black hole X-ray binary produces hard X-ray radiation from its corona and disk when the accreting matter heats up. During an outburst, the disk and corona co-evolve with each other. MAXI J1820 + 070 (ASASSN-18ey) is a low-mass BH X-ray binary, discovered in X-rays with MAXI on 11 March 2018. During the 2018 outburst, this source underwent the rising hard state, the soft state, and then the decaying hard state. In this talk, I will review the recent studies on this source, mainly concentrating on the geometrical and dynamic evolutions of the disk and corona. In the rising hard state, the outflowing corona and its evolution will be discussed by presenting the X-ray spectral analysis of HXMT-Insight observation. And, in the decaying hard state, the disk is found to recede over time, and the corona reaches the Magnetically Arrested Disk (MAD) state, with the radio/optical/X-ray high-cadence observations.

Speaker: Bei You (Wuhan University)

18:30 → 20:30 Banquet

Thursday 12 December

09:00 → 10:25 12-1

Chair: M. Shidatsu (Ehime U.)

09:00 Understanding accretion from Black Hole Binaries

The transient X-ray outbursts of galactic binaries give some of the most spectacular lightcurves seen by MAXI and other monitoring instruments. I will review what these reveal about the accretion flow, and how it links to the transient radio jets. The luminous accretion flow also powers winds, now revealed in exquisite detail in XRISM, and I will speculate on how these relate to the accretion flow, and how we can piece all of this behaviour together into a physically motivated picture.

Speaker: Chris Done (university of durham)

09:20 Important roles of accretion rings in X-ray binaries

In a steady mass flow from a companion star to a compact object in an X-ray binary, the inflowing matter from the companion star is expected to carry a certain amount of specific angular momentum and to first form a geometrically thick ring tube along the Keplerian circular orbit, which is called the accretion ring. A study of the accretion ring by Inoue (2021, PASJ, 73, 795) showed that a pair of inward (accretion) and outward (excretion) flows emerges as the result of angular momentum transfer from the inner side to the outer side of the ring and that each of the oppositely directed flows has a two-layer structure in which a thin disk is sandwiched by a thick flow. Here, we present several observational phenomena in which the accretion ring can be considered to play important roles: 1) The two-layer accretion flows can well explain the overall properties of long term variabilities of black hole X-ray binaries in the high/soft state and the low/hard state. 2) The thick excretion flow can be an origin of the disk winds often observed from X-ray binaries. 3) The periodic precsssing motion can be excited for the accretion ring, inducing the cyclic obscuration of the central X-ray source, observed as a variable source with the super-orbital period. 4) The two-layer excretion flows and the precessing motion can interpret several properties of SS433. 5) In addition, the broad line region in AGNs is possible to be regarded as the accretion ring around the super-massive black hole.

Speaker: Hajime Inoue (ISAS/JAXA)

09:35 Magnetic Heating as the Origin of Bright Hard State in Black Hole Candidates

We present the results of three-dimensional global radiation magnetohydrodynamic simulations of state transitions in black hole candidates. During the hard-to-soft state transition, accretion flow near the black hole tends to be in optically thin hot state even when the accretion rate exceeds the upper limit for RIAF in the outer region. In such state, RIAF near the black hole co-exists with the outer radiatively cooled disk. We found that the temperature of the radiatively cooled disk is higher than the standard disk because the magnetic energy enhanced around the interface between RIAF and the cooled disk is transported radially outward around the equatorial region and heats the disk by releasing the magnetic energy through magnetic reconnection. This non-local heating keeps the disk temperature around 10KeV in stellar mass black holes and 1KeV in super-massive black holes. This mechanism explains the hard X-ray emission in bright hard state and the soft X-ray excess during changing look phenomena in active galactic nuclei,

Speaker: Ryoji Matsumoto (Chiba University)

09:55 20 years of Winds in 4U 1630-47

Despite having one of the most detailed outburst coverage among BHLMXBs, the long term behavior of the wind in 4U 1630-47 remains poorly known. We thus performed an exhaustive study of archival X-ray observations of the source, combining Chandra, NICER, NuSTAR, Suzaku and XMM-Newton, for more than 200 epochs spanned over 9 separate outbursts and two decades, complemented by Swift-BAT and INTEGRAL. I will present our results for the long term evolution of the lines and wind, including new diagnostics made possible by the high energy coverage.

Speaker: Maxime Parra (Ehime University)

10:10 Tests of driving mechanisms of the accretion disk winds in X-ray binaries

Accretion disk winds in compact objects in low-mass X-ray binaries, suggested by the blue-shifted absorption lines in spectroscopic data, are important phenomena to address the understanding of the physics of AGN feedback. However, the driving mechanisms of the winds are unclear. To tackle this, we build a comprehensive model for X-ray spectra, where the detail line profiles are simulated by Monte-Carlo radiation transfer (MCRT), whose input density/velocity fields are done by the radiation hydrodynamics code. Our models show that the observed spectra are well described by the winds launched at a larger radius driven by radiative heating/acceleration. We also show the new result of high-resolution spectroscopy by microcalorimeters onboard XRISM.

Speaker: Ryota Tomaru (Osaka University)

10:25 → 10:45 break

10:45 → 12:10 12-2

Chair: W. Yuan (National Astronomical Observatories, Chinese Academy of Sciences)

10:45 Dust reverberation mapping on type-2 AGN realized by MAXI and WISE monitor

According to the unified model of active galactic nuclei (AGNs), a dusty torus is formed around a broad-line region, accretion disk, and corona near a supermassive black hole (SMBH), and these structures produce multi-wavelength radiation. Studying the structures in not only type-1 but also type-2 AGNs is important to understand e.g., the growth of a SMBH via mass accretion and the AGN feedback to a host galaxy. The dust reverberation mapping is one of the most powerful methods to determine especially an innermost region of a dusty torus, and it has been performed on a few tens type-1 AGNs by optical and infrared monitors. However, no clear results have been reported on type-2 AGNs so far because strong optical extinction completely hides their disk emission. We therefore focus on an X-ray-bright type-2 AGN NGC 2110, and utilize 2–20 keV variation monitored by MAXI to trace the disk emission, instead of optical variation. Comparing it with 3–5 μm infrared variation observed by WISE, we successfully found a dust reverberation time lag of ~130 days (Noda et al. 2020, MNRAS, 495, 2921). In this presentation, we introduce these results comparing with those in type-1 AGNs, and discuss future studies by the dust reverberation mapping on type-2 AGNs with simultaneous X-ray and infrared monitors.

Speaker: Hirofumi Noda (Tohoku University)

11:05 Early Discovery of TDE Candidates by the Einstein Probe Mission

The Einstein Probe (EP) is a newly launched space mission dedicated to the X-ray all-sky survey and characterization of all kinds of high-energy transients. During the first few months of in-orbit operation, EP has discovered dozens of new X-ray transients with intriguing properties. In this talk, I will present a few typical examples of TDE candidates discovered by EP since its launch, including the first case of TDE spectroscopically confirmed to be located in the outskirts of a galaxy. Its rising, peak, plateau and decay phases have all been observed, supporting it in hosting an IMBH of tens of thousands of solar masses. Then I will introduce some puzzling TDE candidates discovered by EP, which are still being monitored and under investigation. Finally, I will provide some prospects for future discoveries and joint observations of EP with other facilities on TDE sciences.

Speaker: Chichuan Jin (National Astronomical Observatories, Chinese Academy of Sciences)

11:25 Investigation on the broad-band emission and variability of radio-quiet AGN

The broad-band emission (optical/UV to X-ray) of luminous active galactic nuclei (AGNs) is believed to be powered by accretion onto central supermassive black holes, with the optical/UV emission generally explained as from the standard accretion disc, and the X-ray emission often explained as the inverse Compton scattering of the soft photons from the accretion disc in a hot corona above. This talk contains mainly two topics. Firstly, we performed a detailed study on the physical origin of the optical/UV-to-X-ray emission of luminous AGNs based on a sample composed of 23 type I Seyfert galaxies. Our work reveal that the optical/UV emission can be well fitted by a modified disc model with the radial temperature profile Teff(R) ∝ R^{-p} (with p~0.5-0.75, and a median of 0.63), deviating from the predication of the standard disk model of p=0.75 (2) the simultaneous optical/UV-to-X-ray emission can be well fitted by our refined disc-corona model with the corona heated by the magnetic reconnection. Secondly, we will present a recent study on a highly variable low-luminosity AGN NGC 7589, which showed a very strong X-ray variability with flux varied by a factor of over 100 within several months. Multi-epoch optical spectroscopic observations reveal no signs of Seyfert type change, however. The physical origin of the extreme variability remains mysterious and requires further, in-depth investigations.

Speaker: Huaqing Cheng (National Astronomical Observatories, Chinese Academy of Sciences)

11:40 NinjaSAT observation of SRGA J144459.2-604207

NinjaSat is the RIKEN's 6U-size X-ray CubeSat launched on 2023 November 11. The main instrument is Xe-based proportional counter covering the energy range of 2--50~keV. Just after we finished the satellite commissioning in 2024 February, the new X-ray transient SRGA J144459.2-604207 appeared. NinjaSat observed SRGA J1444 from 2024 from February 21 to March 18. Meanwhile, NinjaSat detected 12 Type-I X-ray bursts. The recurrence time of X-ray bursts became longer from 2 hour to 8 hour as the source flux decreased. The recurrent time was found to be almost inversely proportional to the accumulated flux.

Speaker: Tomoshi Takeda (RIKEN/Tokyo university of Science)

11:55 Status of MAXI observations of EM counterparts of GW events

MAXI scans about  85% of the whole sky in its orbital period (92 min) by sweeping the sky with a slit-shaped field-of-view (FOV). It can cover a large localized area of a GW event detected by GW detectors and search for an emission from the area before the time of the GW trigger. From the start of LIGO’s operation, MAXI has searched for X-ray counterparts of GW events and reported on upper limits of X-ray flux in the localized areas starting with GW 150914. In GW 170817, MAXI did not observe GW 170817 at the trigger time because during the high-voltage-off operation. The first observation of the position of GW 170817 was eventually performed 4.6  hours after the trigger, though it was the earliest X-ray observation of the EM counterpart of GW 170817. From LIGO’s Observing Runs 3, we performed the operation carefully expanding HV-on area so that all-sky coverage is achieved. In O4, we have been reporting to GCN the observations of the GW events that satisfied the criteria of False Alert Rate smaller than 20 per year and probability of neutron star merger larger than 5%. We report the observations and the operations for GW EM counterparts by MAXI.

Speaker: Satoshi Sugita (AoyamaGakuin University)

12:10 → 13:30 Lunch

13:30 → 15:10 12-3

Chair: M. Serino (AGU)

13:30 First results of SVOM/ECLAIRs

This talk will start with a presentation of the SVOM mission and the homonymous satellite, which was successfully launched on June 22nd 2024, with a special focus on the ECLAIRs hard X-ray imager. Then, the operations performed during the commissioning and early science phases will be described, along with the tuning of some crucial parameters. This will lead to the description of ECLAIRs in-flight performance and first transient detections. A short conclusion will address the perspectives offered by SVOM for the study of the transient high-energy sky.

Speaker: Jean-Luc Atteia (IRAP - Toulouse)

14:00 Overview of GRBs observed by MAXI

The Monitor of All-sky X-ray Image (MAXI) has been observing the X-ray sky and has detected 164 GRBs since its launch in 2009. MAXI is suitable for detecting transient events such as GRB due to its unique scanning observation. Recently, Low luminosity GRBs (LL GRBs) have become a key in multi-messenger astronomy. However, only a few of these events have been observed by all detectors so far. MAXI has the potential to detect LL GRB with sensitivity in lower energy range. In this study, we performed spectral analysis and estimated the Luminosity Function of GRBs observed by MAXI. Our results show that MAXI is capable of observing LL GRB, as shown by the logN-logS distribution and the derived Luminosity Function.

Speaker: Hiroki Hiramatsu (Aoyama Gakuin University)

14:20 Some Preliminary Results of LEIA - the Pathfinder of Einstein Probe

Lobster Eye Imager for Astronomy (LEIA) is a pathfinder of the wide-field X-ray telescope of the Einstein Probe (EP) mission. The piggyback imager, launched in 2022 July, has a mostly unvignetted field of view of 18°. 6 × 18°.6. Its spatial resolution is in the range of 4–7 arcmin in FWHM and the focal spot effective area is 2–3 square centimeter, both showing only mild fluctuations across the field of view. LEIA has started its regular scientific surveys since Nov. 2022, and has finished its first all sky survey. In this talk, we report on the results from its all sky survey. By now LEIA has detected more than 300 sources, of which more than 60 show high variabilities (more than a factor of 10). These sources have been carefully identified following a series of cross-matches with astronomical data bases and multiwavelength catalogues. It has also caught several fast X-ray transients, including GRB 230307A and two novae.

Speaker: Heyang Liu (National Astronomical Observatories, Chinese Academy of Sciences)

14:40 Magnetar emergence in a peculiar gamma-ray burst from a compact star merger

The central engine that powers gamma-ray bursts (GRBs) is still not identified. Besides hyper- accreting black holes, rapidly spinning and highly magnetized neutron stars, known as millisec- ond magnetars, have been suggested to power both long and short GRBs. Indirect indications of a magnetar engine in these merger sources have been observed in the form of plateau fea- tures present in the X-ray afterglow light curves of some short GRBs. Nevertheless, smoking gun evidence is still lacking for a magnetar engine in short GRBs. Here we present a com- prehensive analysis of the broad-band prompt emission data of a peculiar, very bright GRB 230307A. Despite its apparently long duration, the prompt emission and host galaxy properties are consistent with a compact star merger origin, as suggested by its association with a kilo- nova. More intriguingly, an extended X-ray emission component shows up as the γ-ray emission dies out, signifying the emergence of a magnetar central engine. The magnetar-powered X-ray emission is regared as one of the promising EM counterparts of gravitational wave events from compact binary mergers, and would be crucial for identifying the merger remnants. Future multi-messenger observations of similar events hold the promise of unveiling the identity of the progenitor of the peculiar systems such as GRB 230307A.

Speaker: Hui Sun (National Astronomical Observatories, Chinese Academy of Sciences)

14:55 Exploring New Opportunities in Time Domain Astronomy with the CATCH Space Mission

The Chasing All Transients Constellation Hunters (CATCH) space mission, proposed in 2019, is an AI-controlled astronomical constellation dedicated to monitoring X-ray emissions from tran-sients across the entire sky. The mission aims to enhance our understanding of the extreme uni-verse through X-ray imaging, spectral, timing, and polarization measurements. Plans are also in place to introduce microsatellites in various wavelengths, including optical, ultraviolet, infrared, and gamma-ray, to provide a comprehensive view of dynamic events in the universe. The initial pathfinder, CATCH-1, launched in June 2024 alongside SVOM, is designed to validate X-ray timing technologies with Micro Pore Optics (MPO) and a 4-pixel Silicon Drift Detector (SDD) array. Future plans include developing several pathfinders, such as CATCH-3, equipped with MPO and CMOS for simultaneous multi-wavelength observations in collaboration with ground-based optical telescopes like WFST (“Mozi”) and Mephisto. Furthermore, recognizing the significance of X-ray polarization, CATCH has designed a polarization pathfinder with lightweight Wolter-I focusing mirrors and Gas Micro Plate Detector (GMPD) system to con-duct rapid, high-sensitivity polarization measurements in the 2-10 keV energy range with a re-sponse time of 5-10 minutes. This pathfinder will also collaborate with missions like EP and SVOM to enhance its observational capabilities for transients in polarization.

Speaker: Qianqing Yin (Institute of High Energy Physics, CAS)

15:10 → 15:15 Concluding remark

Kawai