arXiv subjects

Takaaki Tanaka

Publications and source records attributed to Takaaki Tanaka.

At least 19 recordsLinked to original sources

arXiv2026

Development and Evaluation of a CNN-Based Charged-Particle Event Rejection Algorithm for Soft X-ray Detection in a pnCCD-Based Satellite System

All-sky surveys in the soft X-ray band are essential for detecting transient objects such as high-redshift gamma-ray bursts (GRBs), which provide key insights into the early universe. HiZ-GUNDAM is a future satellite mission designed to detect and localize high-redshift GRBs. Its wide-field X-ray monitor, EAGLE, combines Lobster Eye Optics with a pnCCD imaging detector operating in the 0.4-4 keV band. Because of limited satellite telemetry, full-frame pnCCD images cannot be downlinked, requiring onboard event selection. Charged particles in the space environment produce background events that can be misidentified as X-ray photons, degrading detection sensitivity and potentially triggering false alerts. In this study, we developed a pnCCD readout system and evaluated charged-particle rejection using conventional grade methods and a convolutional neural network (CNN). Performance was evaluated using X-ray events from an Fe-55 source and electron events from a Sr-90 beta source. The CNN reduced the misclassification rate from 10.2-11.9% for conventional grade methods to 3.1% while maintaining a high acceptance rate for X-ray events. The improvement is particularly pronounced at higher deposited energies, reflecting the CNN's ability to distinguish track-like particle events from X-ray events by capturing detailed spatial features of charge distributions. Comparison with a thin-depletion-layer CMOS sensor further indicates that the thicker depletion layer of the pnCCD enhances discrimination performance. These results demonstrate that CNN-based event classification can substantially reduce charged-particle contamination while maintaining high X-ray acceptance, making it a promising approach for onboard event selection in future pnCCD-based wide-field X-ray missions.

astro-ph.IM↗

arXiv2026

The Supernova Remnant G284.3$-$1.8 and Its Relation to the Gamma-ray Binary 1FGL J1018.6$-$5856

G284.3$-$1.8 is a supernova remnant with a radio shell and thermal X-ray emission. Located near its center is the gamma-ray binary 1FGL J1018.6$-$5856, although the physical association between the two systems is not clear yet. Our X-ray spectroscopy with Suzaku reveals that G284.3$-$1.8 and 1FGL J1018.6$-$5856 have compatible absorption column densities of $N_\mathrm{H} = 6\textrm{--}7 \times 10^{21}~\mathrm{cm}^{-2}$, indicating that the two systems have similar distances. The actual distance is determined as $3~\mathrm{kpc}$ using $\mathrm{^{12}CO}$ ($J=1\textrm{--}0$) data obtained with NANTEN. The X-ray spectrum of G284.3$-$1.8 shows a strong K-shell emission line of Mg, confirming that the earlier claim that the SNR is one of the few Mg-rich SNRs. Comparing recent stellar models taking into account the "shell merger" processes, we find that the obtained Mg-to-Ne mass ratio of $M_\mathrm{Mg}/M_\mathrm{Ne} = 0.73^{+0.07}_{-0.03}$ and Si-to-Mg mass ratio of $M_\mathrm{Si}/M_\mathrm{Mg} = 0.44\pm0.03$ suggest a supernova explosion that would have left a neutron star. The characteristics of 1FGL J1018.6$-$5856, on the other hand, are better explained with a model in which its compact object is neutron star. The present results, therefore, would suggest a possible scenario where G284.3$-$1.8 and 1FGL J1018.6$-$5856 are both remnants of a common supernova explosion although further observational tests are necessary.

astro-ph.HE↗

arXiv2025

The first proper motion measurement of the acceleration regions in the large-scale jets of SS 433 powering the W50 nebula

We report on new Chandra ACIS-I observations of the X-ray knots located in the western and eastern lobes of W50 associated with the parsec-scale jets of the Galactic microquasar SS 433. These knots are likely counterparts of the recently detected very-high-energy ($E>100$ GeV) gamma-ray emission by HAWC and H.E.S.S. These findings, together with the ultra-high-energy signal recently reported by the LHAASO collaboration, have established the SS 433/W50 system as a unique jet-driven PeVatron candidate. Combining new and archival Chandra data, we perform the first proper motion search of the X-ray knot structures over a time interval spanning approximately 20 years. We found no statistically significant motion of these knots at the 3$σ$ confidence level, and place an upper limit of $<$ 0.019-0.033$c$ (5,800-9,800 km s$^{-1}$) for the speed of the innermost knots at an assumed distance $d=5.5$ kpc. Combined with the velocities reported in the literature, the upstream speed in the shock rest frame would reach several 10$^4$ km s$^{-1}$, suggesting that highly efficient particle acceleration, approaching the Bohm limit, is occurring. The absence of significant motion of the knots suggests the presence of a standing recollimation shock, formed by the balance between the jet pressure and the external pressure. This interpretation is consistent with the expected occurrence of such shocks at 20-30 pc from SS 433, matching the location of the observed knots.

astro-ph.HE↗

arXiv2025

Turbulent Magnetic Fields and Molecular Cloud Interactions in the Supernova Remnant G1.9+0.3

We present on results of a spatially resolved spectral analysis of G1.9+0.3, the youngest known supernova remnant in the Galaxy. The X-ray spectra are well described by synchrotron emission from a power-law electron distribution with an exponential cutoff. We found a cutoff energy $ε_0 \sim 1 ~ \rm{keV}$ in both the radio bright rim and the X-ray bright rims. In the loss-limited case, the cutoff energy depends on the shock velocity $v_{\rm{sh}}$ and the Bohm factor $η$, following the relation $ε_0 \propto v_{\rm{sh}}^2 η^{-1} $. Our analysis shows that $η$ ranges from 2 to 4 in the radio rim and from 12 to 15 in the X-ray rims. This suggests that the magnetic field in the radio rim is more turbulent than in the X-ray rims. The presence of CO clouds along the radio rim likely contributes to this difference. Interaction between the shock and these clouds can slow the shock down and generate turbulent eddies. The resulting turbulence eddies can amplify the magnetic field. We propose that the strong radio emission from the radio rim is primarily due to this amplified magnetic field. In contrast, a CO cloud located in the south-west appears to lie in the foreground, as indicated by its low turbulence and the absence of shock deceleration.

astro-ph.HE↗

arXiv2025

Resolving the origin of the unidentified TeV source HESS J1626-490 as a relic of the ancient cosmic-ray factory SNR G335.2+0.1

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

astro-ph.HE↗

arXiv2025

X-ray Study on Propagation of Non-thermal Particles in Microquasar SS 433/W 50 Extended Jets

SS 433, located at the center of the W 50 radio nebula, is a binary system that ejects jets oriented east-west with precessional motion. X-ray lobes, containing compact "knots" labeled as head (e1), lenticular (e2), and ring (e3) in the east, as well as w1, w1.5, and w2 in the west, have been detected along the jets directions. Very-high-energy γ-ray emission has also been detected from regions containing these X-ray knots, suggesting highly efficient particle acceleration in the jets. In our previous study, we performed X-ray imaging spectroscopy of the western lobe of W 50 to investigate spectral variations. In this work, we extend our study to the eastern region using XMM-Newton observations to provide a more comprehensive picture of the X-ray emission from the SS 433 jets. Our results show no detectable synchrotron emission between SS 433 and the innermost knot (head). We also found that the X-ray spectrum of the eastern jet gradually steepens as one moves away from SS 433. While a similar spectral evolution is observed in the western jet, there are also noticeable differences. In the western lobe, the spectrum initially gradually steepens and then undergoes an abrupt softening outside the knot w2. However, in the eastern jet, no such rapid steepening is observed at the lenticular knot, which corresponds to w2 in the west. Furthermore, the observed brightening and spectral variations in the eastern jet cannot be explained by simply adjusting the parameters of the model used for the western side, suggesting the involvement of additional physical processes such as particle re-acceleration.

astro-ph.HE↗

arXiv2025

In-orbit Performance of the Soft X-ray Imaging Telescope Xtend aboard XRISM

We present a summary of the in-orbit performance of the soft X-ray imaging telescope Xtend onboard the XRISM mission, based on in-flight observation data, including first-light celestial objects, calibration sources, and results from the cross-calibration campaign with other currently-operating X-ray observatories. XRISM/Xtend has a large field of view of $38.5'\times38.5'$, covering an energy range of 0.4--13 keV, as demonstrated by the first-light observation of the galaxy cluster Abell 2319. It also features an energy resolution of 170--180 eV at 6 keV, which meets the mission requirement and enables to resolve He-like and H-like Fe K$α$ lines. Throughout the observation during the performance verification phase, we confirm that two issues identified in SXI onboard the previous Hitomi mission -- light leakage and crosstalk events -- are addressed and suppressed in the case of Xtend. A joint cross-calibration observation of the bright quasar 3C273 results in an effective area measured to be $\sim420$ cm$^{2}$@1.5 keV and $\sim310$ cm$^{2}$@6.0 keV, which matches values obtained in ground tests. We also continuously monitor the health of Xtend by analyzing overclocking data, calibration source spectra, and day-Earth observations: the readout noise is stable and low, and contamination is negligible even one year after launch. A low background level compared to other major X-ray instruments onboard satellites, combined with the largest grasp ($Ω_{\rm eff}\sim60$ ${\rm cm^2~degree^2}$) of Xtend, will not only support Resolve analysis, but also enable significant scientific results on its own. This includes near future follow-up observations and transient searches in the context of time-domain and multi-messenger astrophysics.

astro-ph.IM↗

arXiv2025

Development of the Timing System for the X-Ray Imaging and Spectroscopy Mission

This paper describes the development, design, ground verification, and in-orbit verification, performance measurement, and calibration of the timing system for the X-Ray Imaging and Spectroscopy Mission (XRISM). The scientific goals of the mission require an absolute timing accuracy of 1.0~ms. All components of the timing system were designed and verified to be within the timing error budgets, which were assigned by component to meet the requirements. After the launch of XRISM, the timing capability of the ground-tuned timing system was verified using the millisecond pulsar PSR~B1937+21 during the commissioning period, and the timing jitter of the bus and the ground component were found to be below $15~μ$s compared to the NICER (Neutron star Interior Composition ExploreR) profile. During the performance verification and calibration period, simultaneous observations of the Crab pulsar by XRISM, NuSTAR (Nuclear Spectroscopic Telescope Array), and NICER were made to measure the absolute timing offset of the system, showing that the arrival time of the main pulse with XRISM was aligned with that of NICER and NuSTAR to within $200~μ$s. In conclusion, the absolute timing accuracy of the bus and the ground component of the XRISM timing system meets the timing error budget of $500~μ$s.

astro-ph.IM↗

arXiv2025

New CCD Driving Technique to Suppress Anomalous Charge Intrusion from Outside the Imaging Area for Soft X-ray Imager of Xtend onboard XRISM

The Soft X-ray Imager (SXI) is an X-ray CCD camera of the Xtend system onboard the X-Ray Imaging and Spectroscopy Mission (XRISM), which was successfully launched on September 7, 2023 (JST). During ground cooling tests of the CCDs in 2020/2021, using the flight-model detector housing, electronic boards, and a mechanical cooler, we encountered an unexpected issue. Anomalous charges appeared outside the imaging area of the CCDs and intruded into the imaging area, causing pulse heights to stick to the maximum value over a wide region. Although this issue has not occurred in subsequent tests or in orbit so far, it could seriously affect the imaging and spectroscopic performance of the SXI if it were to happen in the future. Through experiments with non-flight-model detector components, we successfully reproduced the issue and identified that the anomalous charges intrude via the potential structure created by the charge injection electrode at the top of the imaging area. To prevent anomalous charge intrusion and maintain imaging and spectroscopic performance that satisfies the requirements, even if this issue occurs in orbit, we developed a new CCD driving technique. This technique is different from the normal operation in terms of potential structure and its changes during imaging and charge injection. In this paper, we report an overview of the anomalous charge issue, the related potential structures, the development of the new CCD driving technique to prevent the issue, the imaging and spectroscopic performance of the new technique, and the results of experiments to investigate the cause of anomalous charges.

astro-ph.IM↗

arXiv2025

Initial operations of the Soft X-ray Imager onboard XRISM

XRISM (X-Ray Imaging and Spectroscopy Mission) is an astronomical satellite with the capability of high-resolution spectroscopy with the X-ray microcalorimeter, Resolve, and wide field-of-view imaging with the CCD camera, Xtend. Xtend consists of the mirror assembly (XMA: X-ray Mirror Assembly) and detector (SXI: Soft X-ray Imager). The SXI is composed of CCDs, analog and digital electronics, and a mechanical cooler. After the successful launch on September 6th, 2023 (UT) and subsequent critical operations, the mission instruments were turned on and set up. The CCDs have been kept at the designed operating temperature of $-110^\circ$C after the electronics and cooling system were successfully set up. During the initial operation phase, which continued for more than a month after the critical operations, we verified the observation procedure, stability of the cooling system, all the observation options with different imaging areas and/or timing resolutions, and time-tagged and automated operations including those for South Atlantic Anomaly passages. We optimized the operation procedure and observation parameters including the cooler settings, imaging areas for the small window modes, and event selection algorithm. We summarize our policy and procedure of the initial operations for the SXI. We also report on a couple of issues we faced during the initial operations and lessons learned from them.

astro-ph.IM↗

arXiv2025

Soft X-ray Imager of the Xtend system onboard XRISM

The Soft X-ray Imager (SXI) is the X-ray charge-coupled device (CCD) camera for the soft X-ray imaging telescope Xtend installed on the X-ray Imaging and Spectroscopy Mission (XRISM), which was adopted as a recovery mission for the Hitomi X-ray satellite and was successfully launched on 2023 September 7 (JST). In order to maximize the science output of XRISM, we set the requirements for Xtend and find that the CCD set employed in the Hitomi/SXI or similar, i.e., a $2 \times 2$ array of back-illuminated CCDs with a $200~μ$m-thick depletion layer, would be practically best among available choices, when used in combination with the X-ray mirror assembly. We design the XRISM/SXI, based on the Hitomi/SXI, to have a wide field of view of $38' \times 38'$ in the $0.4-13$ keV energy range. We incorporated several significant improvements from the Hitomi/SXI into the CCD chip design to enhance the optical-light blocking capability and to increase the cosmic-ray tolerance, reducing the degradation of charge-transfer efficiency in orbit. By the time of the launch of XRISM, the imaging and spectroscopic capabilities of the SXI has been extensively studied in on-ground experiments with the full flight-model configuration or equivalent setups and confirmed to meet the requirements. The optical blocking capability, the cooling and temperature control performance, and the transmissivity and quantum efficiency to incident X-rays of the CCDs are also all confirmed to meet the requirements. Thus, we successfully complete the pre-flight development of the SXI for XRISM.

astro-ph.IM↗

arXiv2025

A detailed study on spectroscopic performance of SOI pixel detector with a pinned depleted diode structure for X-ray astronomy

We have been developing silicon-on-insulator (SOI) pixel detectors with a pinned depleted diode (PDD) structure, named "XRPIX", for X-ray astronomy. In our previous study, we successfully optimized the design of the PDD structure, achieving both the suppression of large leakage current and satisfactory X-ray spectroscopic performance. Here, we report a detailed study on the X-ray spectroscopic performance of the XRPIX with the optimized PDD structure. The data were obtained at $-60^\circ\mathrm{C}$ with the "event-driven readout mode", in which only a triggering pixel and its surroundings are read out. The energy resolutions in full width at half maximum at 6.4 keV are $178\pm1$ eV and $291\pm1$ eV for single-pixel and all-pixel event spectra, respectively. The all-pixel events include charge-sharing pixel events as well as the single-pixel events. These values are the best achieved in the history of our development. We argue that the gain non-linearity in the low energy side due to excessive charge injection to the charge-sensitive amplifier is a major factor to limit the current spectroscopic performance. Optimization of the amount of the charge injection is expected to lead to further improvement in the spectroscopic performance of XRPIX, especially for the all-pixel event spectrum.

astro-ph.IM↗

arXiv2024

Detection of extended X-ray emission around the PeVatron microquasar V4641 Sgr with XRISM

A recent report on the detection of very-high-energy gamma rays from V4641 Sagittarii (V4641 Sgr) up to ~0.8 peta-electronvolt has made it the second confirmed "PeVatron" microquasar. Here we report on the observation of V4641 Sgr with X-Ray Imaging and Spectroscopy Mission (XRISM) in September 2024. Thanks to the large field of view and low background, the CCD imager Xtend successfully detected for the first time X-ray extended emission around V4641 Sgr with a significance of > 4.5 sigma and > 10 sigma based on our imaging and spectral analysis, respectively. The spatial extent is estimated to have a radius of $7 \pm 3$ arcmin ($13 \pm 5$ pc at a distance of 6.2 kpc) assuming a Gaussian-like radial distribution, which suggests that the particle acceleration site is within ~10 pc of the microquasar. If the X-ray morphology traces the diffusion of accelerated electrons, this spatial extent can be explained by either an enhanced magnetic field (~80 uG) or a suppressed diffusion coefficient (~$10^{27}$ cm$^2$ s$^{-1}$ at 100 TeV). The integrated X-ray flux, (4-6)$\times 10^{-12}$ erg s$^{-1}$ cm$^{-2}$ (2-10 keV), would require a magnetic field strength higher than the galactic mean (> 8 uG) if the diffuse X-ray emission originates from synchrotron radiation and the gamma-ray emission is predominantly hadronic. If the X-rays are of thermal origin, the measured extension, temperature, and plasma density can be explained by a jet with a luminosity of ~$2\times 10^{39}$ erg s$^{-1}$, which is comparable to the Eddington luminosity of this system.

astro-ph.HE↗

arXiv2024

Exploring the circumstellar environment of Tycho's supernova remnant. II. Impact on the broadband non-thermal emission

While the environment around Tycho's supernova remnant (SNR) has long been believed to be close to homogeneous, the latest analysis of Chandra data has identified a substantial deceleration of the forward shock which poses a major challenges to this picture. arXiv:2310.14841 showed that the existence of dense molecular cloud (MC) surrounding a rarefied wind-like circumstellar matter (CSM) can explain this observational finding in term of the shock-expansion dynamics, supporting the so-called single-degenerate scenario for the progenitor system. We here extend this work to study the non-thermal emission processes and investigate whether such an environment is consistent with the observed multi-wavelength spectrum. While the simulated broadband spectrum based on the wind-MC environment is largely consistent with observations, we find that such an environment predicts a harder gamma-ray spectrum than observed due to the relatively low CSM density in the cavity interior of the MC. This difference can be at least partially attributed to the present one-dimensional setup of the model which does not account for the clumpy and multi-dimensional structure of the CSM. Our model provides predictions for the long-term evolution of the broadband spectrum which can be used to further probe Tycho's surrounding environment in the future, a key to resolving the long-standing issue of type Ia supernova progenitor channels.

astro-ph.HE↗

arXiv2024

Observational Evidence for Magnetic Field Amplification in SN 1006

We report the first observational evidence for magnetic field amplification in the north-east/south-west (NE/SW) shells of supernova remnant SN 1006, one of the most promising sites of cosmic ray (CR) acceleration. In previous studies, the strength of magnetic fields in these shells was estimated to be $B_{\rm SED}$ $\simeq$ 25$μ$G from the spectral energy distribution, where the synchrotron emission from relativistic electrons accounted for radio to X-rays, along with the inverse Compton emission extending from the GeV to TeV energy bands. However, the analysis of broadband radio data, ranging from 1.37~GHz to 100~GHz, indicated that the radio spectrum steepened from $α_1 = 0.52 \pm 0.02$ to $α_2 = 1.34 \pm 0.21$ by $Δα$ = 0.85 $\pm$ 0.21. This is naturally interpreted as a cooling break under strong magnetic field of $B_{\rm brk}$ $\ge$ 2~mG. Moreover, the high-resolution MeerKAT image indicated that the width of the radio NE/SW shells was broader than that of the X-ray shell by a factor of only 3$-$20, as measured by Chandra. Such narrow radio shells can be naturally explained if the magnetic field responsible for the radio emissions is $B_{\rm R}$ $\ge$ 2 mG. Assuming that the magnetic field is locally enhanced by a factor of approximately $a$ = 100 along the NE/SW shells, we argue that the filling factor, which is the volume ratio of such a magnetically enhanced region to that of the entire shell, must be as low as approximately $k$ = 2.5$\times$10$^{-5}$.

astro-ph.HE↗

arXiv2024

Status of Xtend telescope onboard X-Ray Imaging and Spectroscopy Mission (XRISM)

Xtend is one of the two telescopes onboard the X-ray imaging and spectroscopy mission (XRISM), which was launched on September 7th, 2023. Xtend comprises the Soft X-ray Imager (SXI), an X-ray CCD camera, and the X-ray Mirror Assembly (XMA), a thin-foil-nested conically approximated Wolter-I optics. A large field of view of $38^{\prime}\times38^{\prime}$ over the energy range from 0.4 to 13 keV is realized by the combination of the SXI and XMA with a focal length of 5.6 m. The SXI employs four P-channel, back-illuminated type CCDs with a thick depletion layer of 200 $μ$m. The four CCD chips are arranged in a 2$\times$2 grid and cooled down to $-110$ $^{\circ}$C with a single-stage Stirling cooler. Before the launch of XRISM, we conducted a month-long spacecraft thermal vacuum test. The performance verification of the SXI was successfully carried out in a course of multiple thermal cycles of the spacecraft. About a month after the launch of XRISM, the SXI was carefully activated and the soundness of its functionality was checked by a step-by-step process. Commissioning observations followed the initial operation. We here present pre- and post-launch results verifying the Xtend performance. All the in-orbit performances are consistent with those measured on ground and satisfy the mission requirement. Extensive calibration studies are ongoing.

astro-ph.IM↗

arXiv2024

A dynamical model for IRAS 00500+6713: the remnant of a type Iax supernova SN 1181 hosting a double degenerate merger product WD J005311

IRAS 00500+6713 is a hypothesized remnant of a type Iax supernova SN 1181. Multi-wavelength observations have revealed its complicated morphology; a dusty infrared ring is sandwiched by the inner and outer X-ray nebulae. We analyze the archival X-ray data taken by XMM-Newton and Chandra to constrain the {angular radius}, mass, and metal abundance of the X-ray nebulae, and construct a theoretical model describing the dynamical evolution of IRAS 00500+6713, including the effects of the interaction between the SN ejecta and the intense wind enriched with carbon burning ashes from the central white dwarf (WD) J005311. We show that the inner X-ray nebula corresponds to the wind termination shock while the outer X-ray nebula to the shocked interface between the SN ejecta and the interstellar matter. The observed X-ray properties can be explained by our model with an {ejecta kinetic} energy of $E_\mathrm{ej} = (0.77 \mbox{--} 1.1)\times 10^{48}$~erg, an ejecta mass of $M_\mathrm{ej} = 0.18\mbox{--}0.53~M_\odot$, if the currently observed wind from WD J005311 started to blow $t_\mathrm{w} \gtrsim 810$ yr after the explosion, i.e., approximately after A.D. 1990. The inferred SN properties are compatible with those of Type Iax SNe and the timing of the wind launch may correspond to the Kelvin-Helmholtz contraction of the oxygen-neon core of WD J005311 that triggered a surface carbon burning. Our analysis supports that IRAS 00500+6713 is the remnant of SN Iax 1181 produced by a double degenerate merger of oxygen-neon and carbon-oxygen WDs, and WD J005311 is the surviving merger product.

astro-ph.SR↗

arXiv2024

Evaluation of the X-ray SOI pixel detector with the on-chip ADC

XRPIX is the monolithic X-ray SOI (silicon-on-insulator) pixel detector, which has a time resolution better than 10 $\rmμ$s as well as a high detection efficiency for X-rays above 10 keV. XRPIX is planned to be installed on future X-ray satellites. To mount on satellites, it is essential that the ADC (analog-to-digital converter) be implemented on the detector because such peripheral circuits must be as compact as possible to achieve a large imaging area in the limited space in satellites. Thus, we developed a new XRPIX device with the on-chip ADC, and evaluated its performances. As the results, the integral non-linearity was evaluated to be 6 LSB (least significant bit), equivalent to 36 eV. The differential non-linearity was less than 0.7 LSB, and input noise from the on-chip ADC was 5~$\rm{e^{-}}$. Also, we evaluated end-to-end performance including the sensor part as well as the on-chip ADC. As the results, energy resolution at 5.9 keV was 294 $\rm{\pm}$ 4 eV in full-width at half maximum for the best pixel.

astro-ph.IM↗