arXiv subjects

Masaru Ueno

Publications and source records attributed to Masaru Ueno.

At least 19 recordsLinked to original sources

arXiv2025

A new candidate of a cluster of galaxies behind the Galactic plane, AX J145732-5901

AX J145732-5901 is an unidentified X-ray source discovered in the ASCA Galactic plane survey. Its extended nature and heavily absorbed X-ray spectrum suggest that AX J145732-5901 is a cluster of galaxies behind the Galactic plane. However, due to limited photon statistics, the spectral shape was not well examined. Using the results of the Galactic ridge X-ray emission and Cosmic X-ray background studies based on the Suzaku observations, we reanalyzed the ASCA data of AX J145732-5901. We confirmed that the source is more extended than the point spread function and the angular size is 14'x10'. The spectrum was heavily absorbed by interstellar matter equivalent to an N_{H} of ~10^{23} cm^{-2} and the emission line feature was confirmed. The spectrum was represented by a thin thermal plasma model with a temperature of 2.6 keV and a redshift of 0.12. Assuming the redshift value, the X-ray luminosity is calculated to be 2.6x10^{44} erg s^{-1} in the 1-10 keV energy band. The observational results indicate that AX J145732-5901 is a cluster of galaxies behind the Galactic plane.

astro-ph.HE↗

arXiv2024

Migrating Existing Container Workload to Kubernetes -- LLM Based Approach and Evaluation

Although Kubernetes has become a widespread open-source system that automates the management of containerized applications, its complexity can be a significant barrier, particularly for application developers unfamiliar with it. One approach employs large language models (LLMs) to assist developers in generating Kubernetes manifests; however it is currently impossible to determine whether the output satisfies given specifications and is comprehensible. In this study, we proposed a benchmarking method for evaluating the effectiveness of LLMs in synthesizing manifests, using the Compose specification -- a standard widely adopted by application developers -- as input. The proposed benchmarking method revealed that LLMs generally produce accurate results that compensate for simple specification gaps. However, we also observed that inline comments for readability were often omitted, and completion accuracy was low for atypical inputs with unclear intentions.

cs.SE↗

arXiv2010

Suzaku Observation of the Anomalous X-ray Pulsar 1E 1841-045

We report the results of a Suzaku observation of the anomalous X-ray pulsar (AXP) 1E 1841-045 at a center of the supernova remnant Kes 73. We confirmed that the energy-dependent spectral models obtained by the previous separate observations were also satisfied over a wide energy range from 0.4 to ~70 keV, simultaneously. Here, the models below ~10 keV were a combination of blackbody (BB) and power-law (PL) functions or of two BBs wit h different temperatures at 0.6 - 7.0 keV (Morii et al. 2003), and that above ~20 keV was a PL function (Kuiper Hermsen Mendez 2004). The combination BB + PL + PL was found to best represent the phase-averaged spectrum. Phase-resolved spectroscopy indicated the existence of two emission regions, one with a thermal and the other with a non-thermal nature. The combination BB + BB + PL was also found to represent the phase-averaged spectrum well. However, we found that this model is physically unacceptable due to an excessively large area of the emission region of the blackbody. Nonetheless, we found that the temperatures and radii of the two blackbody components showed moderate correlations in the phase-resolved spectra. The fact that the same correlations have been observed between the phase-averaged spectra of various magnetars (Nakagawa et al. 2009) suggests that a self-similar function can approximate the intrinsic energy spectra of magnetars below ~10 keV.

astro-ph.HE↗

arXiv2008

X-Ray Emission from Supernova Remnants Observed in the ASCA Galactic Plane Survey

X-ray images and spectra of 5 cataloged supernova remnants (SNRs), G12.0-0.1, G346.6-0.2, G348.5+0.1, G348.7+0.3, and G355.6-0.0, observed in the ASCA galactic plane survey are presented. The sizes of X-ray emission from G12.0-0.1, G348.5+0.1, G348.7+0.3, and G355.6-0.0 are comparable to their radio structures, while that of G346.6-0.2 is smaller than the radio structure. The X-ray spectra of all of the SNRs were heavily absorbed by interstellar matter with N_H>10^{22} cm^{-2}. The spectrum of G355.6-0.0 exhibited emission lines, indicating that the X-ray emission has a thin thermal plasma origin, and was well represented by two-temperature thin thermal emission model. On the other hand, no clear emission line features were found in the spectra of the others and the spectra could be represented by either a thin thermal emission model or a power-law model.

astro-ph↗

arXiv2008

PoGOLite - A High Sensitivity Balloon-Borne Soft Gamma-ray Polarimeter

We describe a new balloon-borne instrument (PoGOLite) capable of detecting 10% polarisation from 200mCrab point-like sources between 25 and 80keV in one 6 hour flight. Polarisation measurements in the soft gamma-ray band are expected to provide a powerful probe into high-energy emission mechanisms as well as the distribution of magnetic fields, radiation fields and interstellar matter. At present, only exploratory polarisation measurements have been carried out in the soft gamma-ray band. Reduction of the large background produced by cosmic-ray particles has been the biggest challenge. PoGOLite uses Compton scattering and photo-absorption in an array of 217 well-type phoswich detector cells made of plastic and BGO scintillators surrounded by a BGO anticoincidence shield and a thick polyethylene neutron shield. The narrow FOV (1.25msr) obtained with well-type phoswich detector technology and the use of thick background shields enhance the detected S/N ratio. Event selections based on recorded phototube waveforms and Compton kinematics reduce the background to that expected for a 40-100mCrab source between 25 and 50keV. A 6 hour observation on the Crab will differentiate between the Polar Cap/Slot Gap, Outer Gap, and Caustic models with greater than 5 sigma; and also cleanly identify the Compton reflection component in the Cygnus X-1 hard state. The first flight is planned for 2010 and long-duration flights from Sweden to Northern Canada are foreseen thereafter.

astro-ph↗

arXiv2006

A Suzaku Observation of the Low-Ionization Fe-Line Emission from RCW 86

The newly operational X-ray satellite Suzaku observed the southwestern quadrant of the supernova remnant (SNR) RCW 86 in February 2006 to study the nature of the 6.4 keV emission line first detected with the Advanced Satellite for Cosmology and Astronomy (ASCA). The new data confirm the existence of the line, localizing it for the first time; most of the line emission is adjacent and interior to the forward shock and not at the locus of the continuum hard emission. We also report the first detection of a 7.1 keV line that we interpret as the K-beta emission from low-ionization iron. The Fe-K line features are consistent with a non-equilibrium plasma of Fe-rich ejecta with n_{e}t <~ 10^9 cm^-3 s and kT_{e} ~ 5 keV. This combination of low n_{e}t and high kT_{e} suggests collisionless electron heating in an SNR shock. The Fe K-alpha line shows evidence for intrinsic broadening, with a width of 47 (34--59) eV (99% error region). The difference of the spatial distributions of the hard continuum above 3 keV and the Fe-K line emission support a synchrotron origin for the hard continuum.

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↗

arXiv2006

A Detailed Observation of a LMC Supernova Remnant DEM L241 with XMM-Newton

We report on an {\it XMM-Newton} observation of the supernova remnant (SNR) \object{DEM L241} in the Large Magellanic Cloud. In the soft band image, the emission shows an elongated structure, like a killifish, with a central compact source. The compact source is point-like, and named as XMMU J053559.3$-$673509. The source spectrum is well reproduced with a power-law model with a photon index of $Γ= 1.57$ (1.51--1.62) and the intrinsic luminosity is $2.2\times 10^{35} \mathrm{ergs s^{-1}}$ in the 0.5--10.0 keV band, with the assumed distance of 50 kpc. The source has neither significant coherent pulsations in $2.0\times 10^{-3}$ Hz--8.0 Hz, nor time variabilities. Its luminosity and spectrum suggest that the source might be a pulsar wind nebula (PWN) in DEM L241. The spectral feature classifies this source into rather bright and hard PWN, which is similar to those in Kes 75 and B0540$-$693. The elongated diffuse structure can be divided into a ``Head'' and ``Tail'', and both have soft and line-rich spectra. Their spectra are well reproduced by a plane-parallel shock plasma ({\it vpshock}) model with a temperature of 0.3--0.4 keV and over-abundance in O and Ne and a relative under-abundance in Fe. Such an abundance pattern and the morphology imply that the emission is from the ejecta of the SNR, and that the progenitor of DEM L241 is a very massive star, more than 20 M\sun. This result is also supported by the existence of the central point source and an OB star association, LH 88. The total thermal energy and plasma mass are $\sim 4\times 10^{50}$ ergs and $\sim 200$ M\sun, respectively.

astro-ph↗

arXiv2005

Simulation study of electron drift and gas multiplication in Micro Pixel Chamber

The physical processes of charge collection and gas multiplication of a Micro Pixel Chamber (mu-PIC) were studied in detail using a three-dimensional simulation. The collection efficiencies of primary electrons and gas multiplication factors were calculated for several electrode structures. Based on those studies, we analyzed the optimization of the electrode structure of the mu-PIC, in order to obtain a high gas gain of more than 10^4 and a simultaneous suppression of discharges. Consequently, we found that these characteristics strongly depend on the substrate thickness and the anode diameter of the mu-PIC. In addition, a gas gain of 10^5 would be expected for a mu-PIC having a thick substrate of > 150um.

physics.ins-det↗

arXiv2004

XMM-Newton Observations of G32.45+0.1and G38.55+0.0: diffuse hard X-ray sources found with the ASCA Galactic Plane Survey

We report on XMM-Newton observations of G32.45+0.1 and G38.55+0.0. These were discovered as diffuse hard X-ray sources with the ASCA Galactic plane survey, but the limited spatial resolution of ASCA could not conclude whether these are truly diffuse or a group of unresolved point-sources. XMM-Newton, with higher spatial resolution than ASCA, confirmed that G32.45+0.1 has a diffuse shell-like structure with a radius of ~4'. The spectrum shows featureless continuum, hence can be fitted with a power-law model of Gamma ~2.2 with an absorption of N_H~5.2*10^{22}cm^{-2}. From this N_H value, we estimate the distance to G32.45+0.1 to be ~17kpc, then the luminosity (in the 0.5-10.0keV band) and radius of the shell are ~9.5*10^{34}ergs/s and ~20pc, respectively. The radio complex sources in the NRAO/VLA Sky Survey (NVSS; 1.4GHz) are globally associated to the X-ray shell of G32.45+0.1. Therefore G32.45+0.1 is likely to be a synchrotron dominant shell-like SNR. No significant diffuse structure was found in the XMM-Newton image of another ASCA diffuse source G38.55+0.0. The upper limit of the observed flux (0.5-10.0keV) is estimated to be 9.0*10^{-13}ergs/cm^2/s being consistent with the ASCA result.

astro-ph↗

arXiv2004

MeV Gamma-Ray Imaging Detector with micro-TPC

We propose a new imaging gamma-ray detector in the MeV region. By measuring the directions and energies of not only a scattered gamma ray but also a recoil electron, the direction of an incident gamma ray would be essentially reconstructed event by event. Furthermore, one of two measured (zenith and azimuth) angles of a recoil electron gives us an additional redundancy which enables us to reject the background events by kinematic constraints. In order to measure the track of a recoil electron, the micro Time Projection Chamber($μ$-TPC) has been developed, which can measure the successive positions of the track of charged particles in a few hundred micron meter pitch. The $μ$-TPC consists of the new type of a gas proportional chamber: micro PIxel gas Chamber ($μ$-PIC) which is one of wireless gas chambers and expected to be robust and stable. Using this $μ$-TPC and the Anger camera for the detection of a scattered gamma ray, we have obtained the first gamma-ray image by the full reconstruction of the direction of gamma rays event by event.

astro-ph↗

arXiv2003

A Discovery of a Peculiar Pulsar in the Small Magellanic Cloud

We report on a peculiar X-ray binary pulsar IKT1 = RXJ0047.3-7312 observed with XMM-Newton in Oct. 2000. The X-ray spectrum is described by a two-component spectrum. The hard component has a broken power-law with respective photon indices of 0.2 and 1.8, below and above the break energy at 5.8 keV. The soft component can be modeled by a blackbody of kT = 0.6 keV. The X-ray flux shows a gradual decrease and periodic variations of about 4000 s. The averaged flux in 0.7-10.0 keV is 2.9x10^-12 ergs/cm^2/s, which is ~10 times brighter than that in a ROSAT observation in Nov. 1999. In addition to the 4000-s variation, we found coherent pulsations of 263 +/- 1 s. These discoveries strengthen the Be/X-ray binary scenario proposed by the ROSAT and ASCA observations on this source, and confirm that most of the hard sources in the Small Magellanic Cloud are X-ray binary pulsars. A peculiar property of this XBP is that the coherent pulsations are found only in the soft component, and the folded light curve shows a flat top shape with a sharp dip. We discuss the nature of this XBP focusing on the peculiar soft component.

astro-ph↗

arXiv2003

Thermal and Non-thermal X-Rays from the LMC Super Bubble 30 Dor C

We report on the discovery of thermal and non-thermal X-rays from the shells of the super bubble (SB) 30 Dor C in the Large Magellanic Cloud (LMC). The X-ray morphology is a nearly circular shell with a radius of about 40 pc, which is bright on the northern and western sides. The spectra of the shells are different from region to region. The southern shell shows clear emission lines, and is well fitted with a model of a thin-thermal plasma (kT = 0.21keV) in non-equilibrium ionization (NEI) plus a power-law component. This thermal plasma is located inside of the H alpha emission, which is the outer edge of the shell of the SB. The northern and western sides of the SB are dim in H alpha emission, but are bright in non-thermal (power-law) X-rays with a photon index of 2.1-2.9. The non-thermal X-ray shell traces the outer boundary of the radio shell. These features of thin-thermal and non-thermal X-rays are similar to those of SN 1006, a prototype of synchrotron X-ray shell, but the non-thermal component of 30 Dor C is about ten-times brighter than that of SN 1006. 30 Dor C is the first candidate of an extragalactic SB, in which energetic electrons are accelerating in the shell. The age is much older than that of SN 1006, and hence the particle acceleration time in this SB may be longer than those in normal shell-like SNRs. We found point-like sources associated with some of tight star clusters. The X-ray luminosity and spectrum are consistent with those of young clusters of massive stars. Point-like sources with non-thermal spectra are also found in the SB. These may be background objects (AGNs) or stellar remnants (neutron stars or black holes).

astro-ph↗

arXiv2003

Performance of a micro-TPC for a time-resolved neutron PSD

We report on the performance of a micro-TPC with a micro pixel chamber($μ$-PIC) readout for a time-resolved neutron position-sensitive detector(PSD). Three-dimensional tracks and the Bragg curves of protons with energies of around 1 MeV were clearly detected by the micro-TPC. More than 95% of gamma-rays of 511 keV were found to be discriminated by simple analysis. Simulation studies showed that the total track length of proton and triton emitted from the $\rm {}^{3}He$(n,p(573 keV))$\rm {}^{3}H(191 keV)$ reaction is about 1.2 cm, and that both particles have large energy losses ($\rm > 200 keV/cm$) in 1 atm Ar+$\rm C_{2}H_{6}(10%)$+${}^{3}$He($< 1%$). These values suit the current performance of the micro-TPC, and we conclude that a time-resolved neutron PSD with spatial resolution of sub-millimeters shall be developed as an application of the micro-TPC.

physics.ins-det↗

arXiv2003

Performance of the TPC with Micro Pixel Chamber Readout: micro-TPC

Micro-TPC, a time projection chamber(TPC) with micro pixel chamber($μ$-PIC) readout was developed for the detection of the three-dimensional fine(sub-m illimeter) tracks of charged particles. We developed a two-dimensional position sensitive gaseous detector, or the $μ$-PIC, with the detection area of 10$\times$10 cm${}^{2}$ and 65536 anode electrodes of 400 $μ$m pitch. We achieved the gas gain of over 10000 without any other multipliers. With the pipe-line readout system specially developed for the $μ$-PIC, we detected X-rays at the rate as high as 7.7 Mcps. We attached a drift cage with an 8 cm drift length to the $μ$-PIC and developed a micro-TPC. We measured the basic performances of the micro-TPC and took three-dimensional tracks of electrons. We also developed a prototype of the MeV gamma-ray imaging detector which is a hybrid of the micro-TPC and NaI(Tl) scintillators and confirmed its concept by reconstructing the obtained data.

hep-ex↗

arXiv2003

Fine Structures of Shock of SN 1006 with the Chandra Observation

The north east shell of SN 1006 is the most probable acceleration site of high energy electrons (up to ~ 100 TeV) with the Fermi acceleration mechanism at the shock front. We resolved non-thermal filaments from thermal emission in the shell with the excellent spatial resolution of Chandra. The thermal component is extended widely over about ~ 100 arcsec (about 1 pc at 1.8 kpc distance) in width, consistent with the shock width derived from the Sedov solution. The spectrum is fitted with a thin thermal plasma of kT = 0.24 keV in non-equilibrium ionization (NEI), typical for a young SNR. The non-thermal filaments are likely thin sheets with the scale widths of ~ 4 arcsec (0.04 pc) and ~ 20 arcsec (0.2 pc) at upstream and downstream, respectively. The spectra of the filaments are fitted with a power-law function of index 2.1--2.3, with no significant variation from position to position. In a standard diffusive shock acceleration (DSA) model, the extremely small scale length in upstream requires the magnetic field nearly perpendicular to the shock normal. The injection efficiency (eta) from thermal to non-thermal electrons around the shock front is estimated to be ~ 1e-3 under the assumption that the magnetic field in upstream is 10 micro G. In the filaments, the energy densities of the magnetic field and non-thermal electrons are similar to each other, and both are slightly smaller than that of thermal electrons. in the same order for each other. These results suggest that the acceleration occur in more compact region with larger efficiency than previous studies.

astro-ph↗

arXiv2003

Chandra Observations of a Non-Thermal Supernova Remnant Candidate AX J1843.8-0352 and its Surroundings

We present the Chandra results of AX J1843.8-0352, a supernova remnant (SNR) recently identified with ASCA. Chandra spatially resolved two components from this SNR: non-thermal and thermal ones. The morphology of the non-thermal component is clumpy and elliptical, elongated from the north to the south with a mean diameter of about 9 arcmin. The spectrum is fitted with a power-law model of photon index 2.1 and the east rim is associated with the non-thermal radio sources C and F (Helfand et al. 1989). Therefore the non-thermal component is probably synchrotron X-rays by energetic electrons accelerated at the shell of the SNR. The thermal component is the brightest clump located within the non-thermal component and shows a spectrum of a thin plasma of about 0.7 keV temperature. Notable discovery is its peculiar morphology; a head of 50 arcsec x 30 arcsec size near the south-east rim of the SNR and a 30 arcsec-long ``jet'' pointing to the southwest. Although this emission is associated with the west part of the radio source F, the absorption is twice larger than that of the non-thermal X-rays, or the bulk of the SNR emission. Therefore, it is unclear whether this peculiar plasma is a thermal component associated with AX J1843.8-0352, a Galactic source located in the far side of our Galaxy, or an extragalactic source.

astro-ph↗

arXiv2003

Diffuse Hard X-ray Sources Discovered with the ASCA Galactic Plane Survey

We found diffuse hard X-ray sources, G11.0+0.0, G25.5+0.0, and G26.6-0.1 in the ASCA Galactic plane survey data. The X-ray spectra are featureless with no emission line, and are fitted with both models of a thin thermal plasma in non-equilibrium ionization and a power-law function. The source distances are estimated to be 1-8 kpc, using the best-fit NH values on the assumption that the mean density in the line of sight is 1 H cm^-3. The source sizes and luminosities are then 4.5-27 pc and (0.8-23)x10^33 ergs/s. Although the source sizes are typical to supernova remnants (SNR) with young to intermediate ages, the X-ray luminosity, plasma temperature, and weak emission lines in the spectra are all unusual. This suggests that these objects are either shell-like SNRs dominated by X-ray synchrotron emission, like SN 1006, or, alternatively, plerionic SNRs. The total number of these classes of SNRs in our Galaxy is also estimated.

astro-ph↗