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...
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.
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 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...
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...
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...
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...
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...
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...
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 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...
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...
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...
This presentation will review the main, unique, contributions of the INTErnational Gamma-Ray Astrophysics Laboratory, INTEGRAL, to time domain astronomy.
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...
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...
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...
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...
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...
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...
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...
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,...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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,...
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...
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...
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...
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...
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....
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...
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...
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...
LEIA (Lobster Eye Imager for Astronomy) detected a new X-ray transient on November 7, 2022, identified as a superflare event occurring on a nearby RS CVn-type binary HD 251108. The flux increase was also detected in follow-up observations at X-ray, UV and optical wavelengths. The flare lasted for about forty days in soft X-ray observations, reaching a peak luminosity of ∼ 1.1 × 10^34 erg s^−1...
MAXI is one of the most successful astronomy mission satellites which discovered 14 Galactic X-ray binaries to date. We studied the accretion flow properties of 7 black hole candidates (BHCs; such as MAXI J1659-152, MAXI J1836-194, MAXI J1543-564, MAXI J1535-571, MAXI J1348-630, MAXI J1813-095, MAXI J1910-057) using one of the generalized physical accretion flow models, namely Two-component...
The core of active galactic nuclei (AGN) may be surrounded by numerous clouds in diverse physical states. These clumpy clouds can randomly obscure the central X-ray source, leading to eclipse events. Recent studies indicated that such events are likely common in AGN. However, the complete eclipse events are rarely discovered, because they require extensive X-ray monitoring spanning years. In...
As China's first X-ray astronomy satellite, the Hard X-ray Modulation Telescope (HXMT) has been successfully operational in orbit for about 7 years. It is equipped with three payloads, covering band ranging from 1 to 250 keV. This poster aims to provide a comprehensive overview of HXMT's operational status, with a focus on its scientific proposals, data products, the performance of its three...
We, Science Satellite Operation and Data Archive Unit (C-SODA) in JAXA, have developed FTOOLS-based software (mxsim_psf and mxsim_bgd), which can make simulations of point spread function (PSF) and non X-ray background (NXB) of MAXI/GSC. These tools will be released from HEASARC, soon. By using these tools, we start to develop a tool to make MAXI/GSC light curves obtained by image-fits using...
In the past two decades, multi-wavelength observations of astronomical objects and phenomena using electromagnetic waves have become commonplace. Furthermore, multi-messenger astronomy, which includes messengers beyond electromagnetic waves, such as gravitational waves and neutrinos, is emerging as the new standard. The Multi-Messenger Observation Database and Viewer compile and visualize...
MAXI J1631-479 was discovered on 2018 December 21 by MAXI, and exhibited a fast rise and exponential decay type of the outburst. After the low/hard state at the beginning of the outburst, the source underwent a variety of state transitions. The source, however, had been mostly in the high/soft state after about 100 days from the discovery until the X-ray flux decreased by about four orders of...
Black hole X-ray binaries (BHXRBs) undergo hard-soft-hard state during their outbursts. In the soft state, the energy spectrum is dominated by thermal emission from the accretion disk, which is thought to extend down to the innermost stable circular orbit. In contrast, during the hard state, the disk is truncated at a larger radius, and the spectrum is dominated by a comptonization component...
The first detectable light of a supernova explosion is the shock breakout emission, which is produced as the supernova shock wave breaches the star's surface and which acts as a powerful diagnostic for the pre-explosion state of the progenitor system. I will discuss a novel way of categorizing the possible spectra observed immediately after breakout, and the recent advances in shock breakout...
We develop a new deconvolution method to recover the Crab Nebula image taken by the Hitomi HXT. To suppress the artifact due to the bright Crab pulsar located at the center of the Crab Nebula, we extend the Richardson-Lucy method. Here, we introduce two components corresponding to the nebula and pulsar with regularization for smoothness and flux, respectively, and we perform simultaneous...
A strong solar flare of X6.3 class occurred on February 22, 2024. X-rays from the solar flare are reflected by the moon, MAXI captured the fluorescent X-rays. MAXI detected emission lines of three elements, Si, Ca, and Fe. Those were consistent with the main elements of the moon surface. We considered a model of the reflected X-rays by the moon and compared the intensities of the calculated...
We analyzed 186 cluster of galaxies with MAXI and obtained luminosity, temperature, and abundance. Significant abundance was obtained from 32 clusters, whose average was 0.29 +- 0.06. It is consistent with the previous works. The temperature was obtained from 179 clusters, from which the relation between the luminosity and temperature was obtained as L is proportional to T^4.01. This value was...
Extragalactic Fast X-ray Transients (eFXTs) are defined as short flares in X ray with cosmological origins. But the nature of eFXT is still uncertain due to the lack of timely follow up observations. The possible physical mechanisms include the shock breakout of a supernova, the fireball phase of a nova, the magnetar powered X-ray emission after the mergers of binary neutron stars, off-axis...
We report the X-ray timing results of the black hole candidate MAXI J1820+070 during its 2018 outburst using the Hard X-ray Modulation Telescope (Insight-HXMT) and Neutron Star Interior Composition Explorer Mission (NICER) observations. Low-frequency quasi-periodic oscillations (LFQPOs) are detected in the low/hard state and the hard intermediate state, which lasted for ∼90 days. Thanks to the...
Swift/BAT first reported the detection of the X-ray transient Swift J1727.8-1613 on 2023 August 24 (Page+2023). Optical observations revealed that Swift J1727.8-1613 has a black hole candidate larger than 3.2 Msun and a K4V donor (Mata Sanchez+2023). Black hole X-ray binaries have an accretion state responsible for the ejection of large-scale or compact jets. The formation process of these...
Pulse profiles of X-ray pulsars are invaluable tools for understanding emission mechanisms, system geometry, and radiation transfer under extreme conditions. By extracting energy-dependent pulse profiles Ferrigno (2023) showed how the changes in the pulse shape at energies corresponding to the cyclotron resonance scattering features, provide a quantitative way of determining the feature main...
The cooling effect of $^{63}$Fe$-$$^{63}$Mn Urca pair on the neutron star surface has been evaluated based on the state-of-the-art shell model calculations which reproduced the experimental spectroscopy results in the neutron-rich N $\sim$ 40 region. It is concluded that $^{63}$Fe$-$$^{63}$Mn could be among the strongest Urca pairs in the neutron star crust. This pair has been identified as...
The Einstein Probe (EP) is an interdisciplinary mission of time-domain and X-ray astronomy. It was launched into orbit from the Xichang satellite launch centre on January 9, 2024. From 2024 July the commissioning and calibration phase was successfully completed and the nominal operations phase has started. The Wide-field X-ray Telescope (WXT), one of the two main payloads on board EP, is to...
XRISM PV observation of the Galactic Center detected an interesting transient source named CXOU J174610.8-290019 within the Xtend FoV. The spectrum shows an intensity ratio of Fe-XXVI and Fe-XXV corresponding to kT>20 keV in comparison with a moderate bremsstrahlung continuum of kT~5 keV. We present the results of spectral and timing analyses.
