arXiv subjects

Hajime Inoue

Publications and source records attributed to Hajime Inoue.

At least 19 recordsLinked to original sources

arXiv2026

Energy transfer from jets to surrounding matter to form lateral lobes in SS433/W50

We first investigate an approximate structure of the top region (TR) of a jet, sandwiched by a front shock from which the surrounding matter (SM) inflows and a rear shock from which the jet matter (JM) inflows. Since pressure in the TR is higher than that in the laterally outer space, both JM and SM flowing in the TR are pressed out from the side of the TR. Supposing a steady flow of SM and JM there, we construct a simplified two dimensional model on a structure of the TR. With help of the model, we next infer what happens when precessing jets go through the surroundings in the SS433-W50 system presuming a supernova remnant (SNR) occupies W50. If we assume reasonable density distributions of the SNR and the interstellar matter in a 10 $\sim$ 100 pc distance range, the density of the surroundings is found to be much higher than that of the jet so that the jet is largely braked in the TR and that outflowing rate of the energy from the side of the TR becomes almost identical to the intrinsic energy flow rate through the jet. The outflowing energy could spread to the ambient space in a form of a bow shock but the situation of the shock propagation in the present case could be peculiar due to the presence of the precession. Particularly, all the mass and the energy outflowing from the inner side of the precession cone is considered to be concentrated around the axis of the precession cone. As the result, mass-compressed and energy-accumulated regions are expected to appear along the precession axis, which could be the origin of the lobes laterally extending from the main sphere of W50 observed in radio and X-rays.

astro-ph.HE↗

arXiv2024

Evolution of massive black hole in galactic nucleus

We propose a scenario for mass evolution of massive black holes (MBH) in galactic nuclei, to explain both the mass correlation of the supermassive black hole (SMBH) with the bulge and the down-sizing behavior of the active galactic nuclei. Primordial gas structures to evolve galactic bulges are supposed to be formed at $z \sim$ 10 and the core region, called the nuclear region (NR) here, is considered to be a place for a MBH to grow to the SMBH. The down-sizing behavior requires the MBH to significantly increase the mass in a time $\sim$ 1 Gyr. The rapid mass increase is discussed to be realized only when the MBH stays in a very high density region such as a core of a molecular cloud throughout the period $\sim$ 1 Gyr. According to these arguments, the MBHs formed from the population III stars born in the mini halos at $z \sim$ 20 - 30 are excluded from the candidates for the seed black hole to the SMBH and only the MBHs from the population II stars born in the core of the central molecular cloud (CMC) in the NR remain as them. The MBHs in the dense core of the CMC started increasing the mass through mass-accretion and the most massive black hole (MMBH) got the most rapid evolution, possibly restraining relatively slow evolutions of the less massive black holes. Dynamical interactions of the MMBH with the ambient MCs induced the wandering motion and the further mass-increase. However, when the MMBH mass exceeded a boundary mass, the dynamical friction with the field stars brakes the MMBH wandering and the mass accretion. This scenario can semi-quantitatively reproduce both the down-sizing behavior and the SMBH mass - bulge mass correlation with reasonable parameter values.

astro-ph.GA↗

arXiv2024

Relativistic jet ejections from slim disks

An ejection mechanism of relativistic jets from slim disks is studied. Since the radiation pressure is dominant in the slim disk, radiative energy flow arises along the pressure gradient in the vertical direction. The divergence of the radiative flux tells us that the radiative energy flow from a bottom layer near the equatorial plane is absorbed by another layer upper than the boundary surface. The absorbed energy accumulates in the upper layer as the matter advances inward and calculations show that the specific energy of the flow in the upper layer can be as large as $\sim c^{2}$ near the black hole when the accretion rate through the upper layer is relatively low. Since the specific energy $\sim c^{2}$ is much larger than the gravitational energy, the height of the upper layer could significantly increase then. Hence, the innermost part of the upper layer after almost all the angular momentum has been removed could have a much larger height than the black hole size and collide with one another around the central axis of the disk, bouncing back from the axis as simultaneously expanding along the axis. The flow is expected to go outward along the central axis and to become supersonic due to the cross-section-change of the flow, getting the relativistic jets finally.

astro-ph.HE↗

arXiv2023

Transient jet ejections associated with limit-cycle behaviors in the very high state of black hole binaries

Ejection mechanism of transient relativistic jets from black hole binaries is studied. Based on the observations of the limit-cycle behaviors of the superluminal jet source, GRS 1915+105, we infer that the transient jet ejections could happen just after the slim disk emerging from the standard disk at some distance runs over the standard disk and reaches the vicinity of the central black hole. The standard disk releases about a half of the gravitational energy in the course of the accretion, but the released radiative energy could be absorbed by the optically thick slim disk covering the standard disk in this situation. Then, since the inward motion of the slim disk is much faster than that of the standard disk, a quantity of energy released by an amount of gas in the standard disk is received by the much smaller amount of gas in the slim disk. As the result, the energy per mass received by the slim disk is expected to be largely amplified and is estimated to get highly relativistic. Since the energy is much larger than the gravitational energy, the height of the slim disk could significantly increase. Hence, the innermost part of the slim disk from which almost all the angular momentum has been transferred outward could have a much larger height than the black hole size and collide with one another around the central axis of the disk, turning to an outward flow along the axis normal to the disk plane. The flow in this direction can be approximated to be that through the de Laval nozzle and could become supersonic near the distance where the flow has the smallest cross section.

astro-ph.HE↗

arXiv2022

Steady jet ejections from the innermost region of advection-dominated accretion flow around a black hole

We study ejection mechanisms for two kinds of steady jets: one observed from black hole binaries in the low/hard state and the other from SS433. The specific energy of the ejected gas is required to be positive for the jets to get to infinity, while that of the accreted gas is naively considered to be negative at the outermost boundary of the accretion flow. To reconcile the opposite sign of the specific energies, we propose a situation where two layers exist in the accretion flow and one layer receives energy from the other sufficiently for the specific energy to be positive. For the steady jets in the low/hard state, the accretion ring at the outermost end of the accretion flow is considered to yield two-layer flow in which a geometrically thick ADAF sandwiches a geometrically thin accretion disk and the thin disk is supposed to turn to another ADAF on the inner side. The energy transfer is expected to occur through turbulent mixing between the two layers and the upper layer is discussed to have the positive specific energy large enough for the terminal velocity to be $\sim$ 0.1 $c$. For the steady jets from SS433, a slim disk is argued to separate into two stratified layers due to the photon diffusion in the direction perpendicular to the equatorial plane under the advection dominated situation. In this case, the specific energy of the upper layer is expected to be positive such that the terminal velocity exceeds 0.2 $c$. The jet ejection process near the black hole is investigated commonly to both the two-layer cases and predicts the jet opening angle becomes as small as 2$^{\circ}$.

astro-ph.HE↗

arXiv2022

Mass flows and their behaviors in the SS433--W50 system

We propose the scenario to interpret the overall observational features of the SS433--W50 system. The most unique features of SS433 are the presence of the precessing, mildly relativistic jets and the obscuration of the central engine, which are considered to be due to a supercritical accretion on to the central compact object. The jets are likely to be ejected from the innermost region of the accretion flow. The concept of the accretion ring (Inoue 2021, PASJ, 73,795) is applied to the outer boundary of the accretion flow and the ring is supposed to have a precession. The accretion ring is expected to extend a two-layer outflow of a thin excretion disk and a thick excretion flow, as well as the accretion flow. The thin excretion disk is discussed to eventually form the optically thick excretion belt along the Roche lobe around the compact object, contributing to the obscuration of the central engine. The thick excretion flow is likely to turn to the supersonic wind (disk wind) with the terminal velocity of $\sim 10^{8}$ cm s$^{-1}$ and to collide with the SNR matter at the distance of $\sim 10^{18}$ cm. The interactions of the jets with the disk wind are considered to cause the features of the jets observed at the distances of 10$^{14} \sim 10^{15}$ cm and $\sim 10^{17}$ cm. Finally, it is discussed that the jets are braked by the SNR matter at the distance of $\sim$10 pc and the momentum carried by the jet is transferred to the SNR matter shoved by the jet. The SNR matter pushed to the inside of the precession cone is expected to gather along the cone axis and to form the elongated structures in the east and west directions from the main W50 structure.

astro-ph.HE↗

arXiv2021

Origin of cool cores, cold fronts and spiral structures in cool core clusters of galaxies

We consider a situation in which a brightest cluster galaxy (BCG) moves in ambient hot gas in the central region of a cool core cluster of galaxies, following the study by Inoue (2014, PASJ, 66, 60). In the rest frame of the BCG, the hot gas is supposed to flow toward the BCG in parallel from a sufficiently large distance. Then, it is expected that only the gas flowing with the impact parameter less than a critical value is trapped by the gravitation field of the BCG because of the efficient radiative cooling, getting a cooling flow, and that the remaining outer gas can get over the potential well. In such a circumstance, we can draw the following picture: A boundary layer between the out-flowing gas and the trapped gas arises around the stagnation point at the back side of the BCG. Since the boundary temperature is so low as to be X-ray dim, the boundary could be observed as the cold front in X-rays. The trapped gas once stagnates on the inner side of the boundary and starts in-falling toward the BCG. Since the wandering motion of the BCG is likely to have a rotational component, the Coriolis force induces a rotational motion in the in-falling flow from the stagnation place to the BCG, forming a spiral structure around the BCG. The spiraling flow turns the BCG on the up stream side of the main flow from the far outside, and arises another boundary layer having contact discontinuity with the main hot gas flow. These pictures well reproduce the observed features such as cool cores, cold fronts, and spiral structures. It can also be resolved how the cooling flow is suppressed from what the cooling flow hypothesis predicts, without any heating mechanism.

astro-ph.HE↗

arXiv2021

Accretion environments of active galactic nuclei

We study accretion environments of active galactic nuclei when a super-massive black hole wanders in a circum-nuclear region and passes through an interstellar medium there. It is expected that a Bondi-Hoyle-Lyttleton type accretion of the interstellar matter takes place and an accretion stream of matter trapped by the black hole gravitational field appears from a tail shock region. Since the trapped matter is likely to have a certain amount of specific angular momentum, the accretion stream eventually forms an accretion ring around the black hole. According to the recent study, the accretion ring consists of a thick envelope and a thin core, and angular momenta are transfered from the inner side facing to the black hole to the opposite side respectively in the envelope and the core. As a result, a thick accretion flow and a thick excretion flow extend from the envelope, and a thin accretion disk and a thin excretion disk do from the core. The thin excretion disk is predicted to terminate at some distance forming an excretion ring, while the thick excretion flow is considered to become a super-sonic wind flowing to the infinity. The thick excretion flow from the accretion ring is expected to interact with the accretion stream toward the accretion ring and to be collimated to bi-polar cones. These pictures provide a likely guide line to interpret the overall accretion environments suggested from observations.

astro-ph.HE↗

arXiv2021

Properties of the accretion ring in an X-ray binary, and accretion and excretion two-layer flows from it

We study properties of an accretion ring in a steady mass flow from a companion star to a compact object in an X-ray binary. The accretion ring is a place where matter inflowing from a companion star sojourns for a while to bifurcate to accretion and excretion flows due to angular momentum transfer in it. The matter in the accretion ring rotates along the Keplerian circular orbit determined by the intrinsic specific angular momentum of the inflowing matter and forms a thick ring-envelope. Two internal flows are expected to appear in the thick envelope. One is a mass spreading flow bifurcating to a thick accretion flow and a thick excretion flow, as a result of the angular momentum transfer within the ring-envelope. The other is a cooling flow toward the envelope center governed by radiative cooling under an effect of X-ray irradiation. This cooling flow eventually forms a core in the torus, from which a thin accretion disk and a thin excretion disk spread out as a result of the angular momentum transfer there again. Evaluating and comparing the time scales for the two internal flows, the accretion ring is shown to generally originate a two-layer accretion flow in which a thin accretion disk is sandwiched by a thick accretion flow, unless the accretion rate is very low. Properties of the thin excretion disk and the thick excretion flow are also investigated. The thin excretion disk is expected to terminate at a distance 4 times as large as the accretion ring radius and to form another ring there, unless tidal effects from the companion star exist. The thick excretion flow is, on the other hand, likely to turn to a super-sonic wind-flow reaching the infinity.

astro-ph.HE↗

arXiv2021

Wandering of the central black hole in a galactic nucleus and correlation of the black hole mass with the bulge mass

We investigate a mechanism for a super-massive black hole at the center of a galaxy to wander in the nucleus region. A situation is supposed in which the central black hole tends to move by the gravitational attractions from the nearby molecular clouds in a nuclear bulge but is braked via the dynamical frictions by the ambient stars there. We estimate the approximate kinetic energy of the black hole in an equilibrium between the energy gain rate through the gravitational attractions and the energy loss rate through the dynamical frictions, in a nuclear bulge composed of a nuclear stellar disk and a nuclear stellar cluster as observed from our Galaxy. The wandering distance of the black hole in the gravitational potential of the nuclear bulge is evaluated to get as large as several 10 pc, when the black hole mass is relatively small. The distance, however, shrinks as the black hole mass increases and the equilibrium solution between the energy gain and loss disappears when the black hole mass exceeds an upper limit. As a result, we can expect the following scenario for the evolution of the black hole mass: When the black hole mass is smaller than the upper limit, mass accretion of the interstellar matter in the circum-nuclear region, causing the AGN activities, makes the black hole mass larger. However, when the mass gets to the upper limit, the black hole loses the balancing force against the dynamical friction and starts spiraling downward to the gravity center. From simple parameter scaling, the upper mass limit of the black hole is found to be proportional to the bulge mass and this could explain the observed correlation of the black hole mass with the bulge mass.

astro-ph.HE↗

arXiv2019

X-ray emissions from magnetic polar regions of neutron stars

Structures of X-ray emitting magnetic polar regions on neutron stars in X-ray pulsars are studied in a range of the accretion rate, 10$^{17}$ g s$^{-1} \sim 10^{18}$ g s$^{-1}$. It is shown that a thin but tall, radiation energy dominated, X-ray emitting polar cone appears at each of the polar regions. The height of the polar cone is several times as large as the neutron star radius. The energy gain due to the gravity of the neutron star in the polar cone exceeds the energy loss due to photon diffusion in the azimuthal direction of the cone, and a significant amount of energy is advected to the neutron star surface. Then, the radiation energy carried with the flow should become so large for the radiation pressure to overcome the magnetic pressure at the bottom of the cone. As a result, the matter should expand in the tangential direction along the neutron star surface, dragging the magnetic lines of force, and form a mound-like structure. The advected energy to the bottom of the cone should finally be radiated away from the surface of the polar mound and the matter should be settled on the neutron star surface there. From such configurations, we can expect an X-ray spectrum composed of a multi-color blackbody spectrum from the polar cone region and a quasi-single blackbody spectrum from the polar mound region. These spectral properties agree with observations. A combination of a fairly sharp pencil beam and a broad fan beam is expected from the polar cone region, while a broad pencil beam is expected from the polar mound region. With these X-ray beam properties, basic patterns of pulse profiles of X-ray pulsars can be explained too.

astro-ph.HE↗

arXiv2019

Reproductions of super-orbital X-ray light-curves with the precessing accretion ring model and implications on accretion flows through accretion rings

X-ray light curves of three X-ray pulsars, SMC X-1, LMC X-4 and Her X-1, folded with their respective super-orbital periods, are shown to be well reproduced by a model in which X-rays from a compact object towards us are periodically obscured by a precessing ring at the outermost part of an accretion disk around the central object. A situation is considered in which matter from a companion star flows into a gravitational field of a compact star carrying a certain amount of specific angular momentum and first forms a geometrically thick ring-tube along the Keplerian circular orbit. For the model to well fit to the observations, it is necessary that the optical depth of the ring-tube for Compton scattering, $τ\simeq 1 \sim 2$, the ring matter temperature, $T \simeq 10^{5} \sim 10^{6}$ K and the ionization parameter, $ξ\simeq 10^{2}$ erg cm s$^{-1}$ due to X-ray heating from the central X-ray source. From simple energetics- and perturbation-arguments, we find that a precession of such a ring is rather stable and possible to be excited in the $T$ and $ξ$ ranges. The time during which matter accumulates in the ring is estimated to be $\sim 10^{6}$ s, and is shown to be comparable to the time for an accretion disk to extend from the ring. It is discussed that in the above $T$ and $ξ$ ranges, the ring-tube matter could become thermally unstable. Then, relatively high density regions in the ring-tube further cools down and tends to shrink to the tube center. The flow across the ring circulating flow should excite turbulent motions, and angular momenta of the matter would be effectively transferred across the tube. Finally, a steady flow should be established from the companion star through the accretion ring to the accretion disk towards the central compact star.

astro-ph.HE↗

arXiv2018

Detection of polarized gamma-ray emission from the Crab nebula with Hitomi Soft Gamma-ray Detector

We present the results from the Hitomi Soft Gamma-ray Detector (SGD) observation of the Crab nebula. The main part of SGD is a Compton camera, which in addition to being a spectrometer, is capable of measuring polarization of gamma-ray photons. The Crab nebula is one of the brightest X-ray / gamma-ray sources on the sky, and, the only source from which polarized X-ray photons have been detected. SGD observed the Crab nebula during the initial test observation phase of Hitomi. We performed the data analysis of the SGD observation, the SGD background estimation and the SGD Monte Carlo simulations, and, successfully detected polarized gamma-ray emission from the Crab nebula with only about 5 ks exposure time. The obtained polarization fraction of the phase-integrated Crab emission (sum of pulsar and nebula emissions) is (22.1 $\pm$ 10.6)% and, the polarization angle is 110.7$^o$ + 13.2 / $-$13.0$^o$ in the energy range of 60--160 keV (The errors correspond to the 1 sigma deviation). The confidence level of the polarization detection was 99.3%. The polarization angle measured by SGD is about one sigma deviation with the projected spin axis of the pulsar, 124.0$^o$ $\pm$0.1$^o$.

astro-ph.HE↗

arXiv2018

Hitomi X-ray Observation of the Pulsar Wind Nebula G21.5$-$0.9

We present results from the Hitomi X-ray observation of a young composite-type supernova remnant (SNR) G21.5$-$0.9, whose emission is dominated by the pulsar wind nebula (PWN) contribution. The X-ray spectra in the 0.8-80 keV range obtained with the Soft X-ray Spectrometer (SXS), Soft X-ray Imager (SXI) and Hard X-ray Imager (HXI) show a significant break in the continuum as previously found with the NuSTAR observation. After taking into account all known emissions from the SNR other than the PWN itself, we find that the Hitomi spectra can be fitted with a broken power law with photon indices of $Γ_1=1.74\pm0.02$ and $Γ_2=2.14\pm0.01$ below and above the break at $7.1\pm0.3$ keV, which is significantly lower than the NuSTAR result ($\sim9.0$ keV). The spectral break cannot be reproduced by time-dependent particle injection one-zone spectral energy distribution models, which strongly indicates that a more complex emission model is needed, as suggested by recent theoretical models. We also search for narrow emission or absorption lines with the SXS, and perform a timing analysis of PSR J1833$-$1034 with the HXI and SGD. No significant pulsation is found from the pulsar. However, unexpectedly, narrow absorption line features are detected in the SXS data at 4.2345 keV and 9.296 keV with a significance of 3.65 $σ$. While the origin of these features is not understood, their mere detection opens up a new field of research and was only possible with the high resolution, sensitivity and ability to measure extended sources provided by an X-ray microcalorimeter.

astro-ph.HE↗

arXiv2017

Temperature Structure in the Perseus Cluster Core Observed with Hitomi

The present paper investigates the temperature structure of the X-ray emitting plasma in the core of the Perseus cluster using the 1.8--20.0 keV data obtained with the Soft X-ray Spectrometer (SXS) onboard the Hitomi Observatory. A series of four observations were carried out, with a total effective exposure time of 338 ks and covering a central region $\sim7'$ in diameter. The SXS was operated with an energy resolution of $\sim$5 eV (full width at half maximum) at 5.9 keV. Not only fine structures of K-shell lines in He-like ions but also transitions from higher principal quantum numbers are clearly resolved from Si through Fe. This enables us to perform temperature diagnostics using the line ratios of Si, S, Ar, Ca, and Fe, and to provide the first direct measurement of the excitation temperature and ionization temperature in the Perseus cluster. The observed spectrum is roughly reproduced by a single temperature thermal plasma model in collisional ionization equilibrium, but detailed line ratio diagnostics reveal slight deviations from this approximation. In particular, the data exhibit an apparent trend of increasing ionization temperature with increasing atomic mass, as well as small differences between the ionization and excitation temperatures for Fe, the only element for which both temperatures can be measured. The best-fit two-temperature models suggest a combination of 3 and 5 keV gas, which is consistent with the idea that the observed small deviations from a single temperature approximation are due to the effects of projection of the known radial temperature gradient in the cluster core along the line of sight. Comparison with the Chandra/ACIS and the XMM-Newton/RGS results on the other hand suggests that additional lower-temperature components are present in the ICM but not detectable by Hitomi SXS given its 1.8--20 keV energy band.

astro-ph.HE↗

arXiv2017

Atomic data and spectral modeling constraints from high-resolution X-ray observations of the Perseus cluster with Hitomi

The Hitomi SXS spectrum of the Perseus cluster, with $\sim$5 eV resolution in the 2-9 keV band, offers an unprecedented benchmark of the atomic modeling and database for hot collisional plasmas. It reveals both successes and challenges of the current atomic codes. The latest versions of AtomDB/APEC (3.0.8), SPEX (3.03.00), and CHIANTI (8.0) all provide reasonable fits to the broad-band spectrum, and are in close agreement on best-fit temperature, emission measure, and abundances of a few elements such as Ni. For the Fe abundance, the APEC and SPEX measurements differ by 16%, which is 17 times higher than the statistical uncertainty. This is mostly attributed to the differences in adopted collisional excitation and dielectronic recombination rates of the strongest emission lines. We further investigate and compare the sensitivity of the derived physical parameters to the astrophysical source modeling and instrumental effects. The Hitomi results show that an accurate atomic code is as important as the astrophysical modeling and instrumental calibration aspects. Substantial updates of atomic databases and targeted laboratory measurements are needed to get the current codes ready for the data from the next Hitomi-level mission.

astro-ph.HE↗

arXiv2017

Hitomi Observations of the LMC SNR N132D: Highly Redshifted X-ray Emission from Iron Ejecta

We present Hitomi observations of N132D, a young, X-ray bright, O-rich core-collapse supernova remnant in the Large Magellanic Cloud (LMC). Despite a very short observation of only 3.7 ks, the Soft X-ray Spectrometer (SXS) easily detects the line complexes of highly ionized S K and Fe K with 16-17 counts in each. The Fe feature is measured for the first time at high spectral resolution. Based on the plausible assumption that the Fe K emission is dominated by He-like ions, we find that the material responsible for this Fe emission is highly redshifted at ~800 km/s compared to the local LMC interstellar medium (ISM), with a 90% credible interval of 50-1500 km/s if a weakly informative prior is placed on possible line broadening. This indicates (1) that the Fe emission arises from the supernova ejecta, and (2) that these ejecta are highly asymmetric, since no blue-shifted component is found. The S K velocity is consistent with the local LMC ISM, and is likely from swept-up ISM material. These results are consistent with spatial mapping that shows the He-like Fe concentrated in the interior of the remnant and the S tracing the outer shell. The results also show that even with a very small number of counts, direct velocity measurements from Doppler-shifted lines detected in extended objects like supernova remnants are now possible. Thanks to the very low SXS background of ~1 event per spectral resolution element per 100 ks, such results are obtainable during short pointed or slew observations with similar instruments. This highlights the power of high-spectral-resolution imaging observations, and demonstrates the new window that has been opened with Hitomi and will be greatly widened with future missions such as the X-ray Astronomy Recovery Mission (XARM) and Athena.

astro-ph.HE↗

arXiv2017

Glimpse of the highly obscured HMXB IGR J16318-4848 with Hitomi

We report a Hitomi observation of IGR J16318-4848, a high-mass X-ray binary system with an extremely strong absorption of N_H~10^{24} cm^{-2}. Previous X-ray studies revealed that its spectrum is dominated by strong fluorescence lines of Fe as well as continuum emission. For physical and geometrical insight into the nature of the reprocessing material, we utilize the high spectroscopic resolving power of the X-ray microcalorimeter (the soft X-ray spectrometer; SXS) and the wide-band sensitivity by the soft and hard X-ray imager (SXI and HXI) aboard Hitomi. Even though photon counts are limited due to unintended off-axis pointing, the SXS spectrum resolves Fe K{α_1} and K{α_2} lines and puts strong constraints on the line centroid and width. The line width corresponds to the velocity of 160^{+300}_{-70} km s^{-1}. This represents the most accurate, and smallest, width measurement of this line made so far from any X-ray binary, much less than the Doppler broadening and shift expected from speeds which are characteristic of similar systems. Combined with the K-shell edge energy measured by the SXI and HXI spectra, the ionization state of Fe is estimated to be in the range of Fe I--IV. Considering the estimated ionization parameter and the distance between the X-ray source and the absorber, the density and thickness of the materials are estimated. The extraordinarily strong absorption and the absence of a Compton shoulder component is confirmed. These characteristics suggest reprocessing materials which are distributed in a narrow solid angle or scattering primarily with warm free electrons or neutral hydrogen.

astro-ph.HE↗