arXiv subjects

Takeshi Tsuru

Publications and source records attributed to Takeshi Tsuru.

8 recordsLinked to original sources

arXiv2026

The First Insights into an Ultraluminous X-ray Pulsar with XRISM: Phase-Resolved High-Resolution Spectroscopy of the Fe K-shell Band of M82 X-2

During the performance verification phase, XRISM observed the M82 galaxy for a net exposure of 207.7 ks, with the ultraluminous X-ray pulsar (ULXP) X-2 included in the field of view. A pulsation search identified a candidate signal with a period close to the previously known value, 1.38727 s, at a significance of $3.15σ$ based on Monte Carlo simulations. Using this candidate period, phase-resolved spectral analysis with the high spectral resolution of Resolve was performed. The spectra suggest that, if the candidate pulsation is real, the Fe K$α$ emission line in the pulse peak phase has a larger width ($36^{+60}_{-13}$ eV) than that in the remaining phase at a significance exceeding $3σ$. This suggests that at least a fraction of the Fe K$α$ emission is associated with the ULXP system. The observed width corresponds to a velocity dispersion of $(1.7^{+2.8}_{-0.6})\times10^3$ km s$^{-1}$, which is too large to be explained by motions in the companion star atmosphere. The rise time of the pulsation constrains the line-emitting region to be smaller than $6.3\times10^4$ km, suggesting an origin in the accretion flow. This work demonstrates the capability of XRISM Resolve for pulsation-resolved high-resolution spectroscopy of ULX pulsars.

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↗

arXiv2023

Xtend, the Soft X-ray Imaging Telescope for the X-ray Imaging and Spectroscopy Mission (XRISM)

Xtend is a soft X-ray imaging telescope developed for the X-Ray Imaging and Spectroscopy Mission (XRISM). XRISM is scheduled to be launched in the Japanese fiscal year 2022. Xtend consists of 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. The SXI uses the P-channel, back-illuminated type CCD with an imaging area size of 31 mm on a side. The four CCD chips are arranged in a 2$\times$2 grid and can be cooled down to $-120$ $^{\circ}$C with a single-stage Stirling cooler. The XMA nests thin aluminum foils coated with gold in a confocal way with an outer diameter of 45~cm. A pre-collimator is installed in front of the X-ray mirror for the reduction of the stray light. Combining the SXI and XMA with a focal length of 5.6m, a field of view of $38^{\prime}\times38^{\prime}$ over the energy range from 0.4 to 13 keV is realized. We have completed the fabrication of the flight model of both SXI and XMA. The performance verification has been successfully conducted in a series of sub-system level tests. We also carried out on-ground calibration measurements and the data analysis is ongoing.

astro-ph.IM↗

arXiv2015

SOI Pixel Sensor for Gamma-Ray Imaging

SOI (Silicon-On-Insulator) pixel sensor is promising technology for developing the high position resolution detector by integrating the small pixels and circuits in the monolithic way. The event driven (trigger mode) SOI based pixel sensor has also been developed for the application of X-ray astronomy with the purpose of reducing the noise using anti-coincidence event. This trigger mode SOI pixel sensor working with in the rate of kilo Hz is also a promising scatter detector for advanced Compton imaging to track the Compton recoiled electrons.

physics.ins-det↗

arXiv2009

Starburst Galaxies: Outflows of Metals and Energy into the IGM

What is the contribution of mass, metals and energy from starburst galaxies to the Intergalactic Medium? Starburst galaxies drive galactic-scale outflows or "superwinds" that may be responsible for removing metals from galaxies and polluting the Intergalactic Medium (IGM). In the last decade tremendous progress was made in mapping cool entrained gas in superwinds through UV/optical imaging and absorption line spectroscopy. These studies demonstrated that superwinds are ubiquitous in galaxies forming stars at high surface densities and that the most powerful starbursts can drive outflows near escape velocity. Theoretical models of galaxy evolution have begun to incorporate superwinds, using various ad-hoc prescriptions based on our knowledge of the cool gas. However, these efforts are fundamentally impeded by our lack of information about the hot phase of these outflows. The hot X-ray emitting phase of a superwind contains the majority of its energy and newly-synthesized metals, and given its high specific energy and inefficient cooling it is also the component most likely escape from the galaxy's gravitational potential well. Knowledge of the chemical composition and velocity of the hot gas are crucial to assess the energy and chemical feedback from a starburst. A high priority for the next decade is to enable direct measurements to be made of the rates at which starburst galaxies of all masses eject gas, metals, and energy into the IGM. This will require a high sensitivity X-ray imaging spectrometer capable of measuring velocities in faint diffuse X-ray emission with a velocity accuracy of ~ 100 km/s. Such spectral resolution automatically allows detailed line-based plasma diagnostics, and thus composition, energetics and flow rates can be derived.

astro-ph.CO↗

arXiv2008

Suzaku Observations of M82 X-1 : Detection of a Curved Hard X-ray Spectrum

A report is presented on Suzaku observations of the ultra-luminous X-ray source X-1 in the starburst galaxy M82, made three time in 2005 October for an exposure of ~ 30 ks each. The XIS signals from a region of radius 3 around the nucleus defined a 2-10 keV flux of 2.1 x 10^-11 erg s-1 cm-2 attributable to point sources. The 3.2-10 keV spectrum was slightly more convex than a power-law with a photon index of 1.7. In all observations, the HXD also detected signals from M82 up to ~ 20 keV, at a 12-20 keV flux of 4.4 x 10^-12 erg s-1 cm-2 . The HXD spectrum was steeper than that of the XIS. The XIS and HXD spectra can be jointly reproduced by a cutoff power-law model, or similar curved models. Of the detected wide-band signals, 1/3 to 2/3 are attributable to X-1, while the remainder to other discrete sources in M82. Regardless of the modeling of these contaminants, the spectrum attributable to X-1 is more curved than a power-law, with a bolometric luminosity of (1.5 -3) x 10 ^40 erg s-1. These results are interpreted as Comptonized emission from a black hole of 100-200 solar masses, radiating roughly at the Eddington luminosity.

astro-ph↗

arXiv2006

Suzaku Observations of HESS J1616-508: Evidence for a Dark Particle Accelerator

We observed the bright unidentified TeV gamma-ray source HESS J1616-508 with the X-ray Imaging Spectrometers onboard the Suzaku satellite. No X-ray counterpart was found to a limiting flux of 3.1e-13 erg/s/cm^2 in the 2--10 keV band, which is some 60 times below the gamma-ray flux in the 1--10 TeV band. This object is bright in TeV gamma-rays but very dim in the X-ray band, and thus is one of the best examples in the Galaxy of a "dark particle accelerator." We also detected soft thermal emission with kT=0.3--0.6 keV near the location of HESSJ1616. This may be due to the dust grain scattering halo from the nearby bright supernova remnant RCW103.

astro-ph↗

arXiv1998

The hardest X-ray source in the ASCA Large Sky Survey: Discovery of a new type 2 Seyfert

We present results of ASCA deep exposure observations of the hardest X-ray source discovered in the ASCA Large Sky Survey (LSS) project, designated as AX J131501+3141. We extract its accurate X-ray spectrum, taking account of the contamination from a nearby soft source (AX J131502+3142), separated only by 1'. AX J131501+3141 exhibits a large absorption of NH = (6 +4 -2)x 10^22 H/cm^2 with a photon index Γ= 1.5 +0.7 -0.6. The 2--10 keV flux was about 5 x 10^-13 erg/s/cm^2 and was time variable by a factor of 30% in 0.5 year. From the highly absorbed X-ray spectrum and the time variability, as well as the results of the optical follow-up observations (Akiyama et al. 1998, astro-ph/9801173), we conclude that AX J131501+3141 is a type 2 Seyfert galaxy. Discovery of such a low flux and highly absorbed X-ray source could have a significant impact on the origin of the cosmic X-ray background.

astro-ph↗