arXiv subjects

Hajime Inoue

Publications and source records attributed to Hajime Inoue.

41 records · Page 3Linked to original sources

arXiv2006

Precision Fe Kalpha and Fe Kbeta Line Spectroscopy of the Seyfert 1.9 Galaxy NGC 2992 with Suzaku

We present detailed time-averaged X-ray spectroscopy in the 0.5--10 keV band of the Seyfert~1.9 galaxy NGC 2992 with the Suzaku X-ray Imaging Spectrometers (XIS). We model the complex continuum in detail. There is an Fe K line emission complex that we model with broad and narrow lines and we show that the intensities of the two components are decoupled at a confidence level >3sigma. The broad Fe K line has an EW of 118 (+32,-61) eV and could originate in an accretion disk (with inclination angle greater than ~30 degrees). The narrow Fe Kalpha line has an EW of 163 (+47,-26) eV and is unresolved FWHM <4090 km/s) and likely originates in distant matter. The absolute flux in the narrow line implies that the column density out of the line-of-sight could be much higher than measured in the line-of-sight, and that the mean (historically-averaged) continuum luminosity responsible for forming the line could be a factor of several higher than that measured from the data. We also detect the narrow Fe Kbeta line with a high signal-to-noise ratio and describe a new robust method to constrain the ionization state of Fe responsible for the Fe Kalpha and Fe Kbeta lines that does not require any knowledge of possible gravitational and Doppler energy shifts affecting the line energies. For the distant line-emitting matter (e.g. the putative obscuring torus) we deduce that the predominant ionization state is lower than Fe VIII (at 99% confidence), conservatively taking into account residual calibration uncertainties in the XIS energy scale and theoretical and experimental uncertainties in the Fe K fluorescent line energies. From the limits on a possible Compton-reflection continuum it is likely that the narrow Fe Kalpha and Fe Kbeta lines originate in a Compton-thin structure.

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arXiv2006

Erratum: ASCA Observations of the Absorption-Line Features from the Super-Luminal Jet Source GRS 1915+105

We have discovered errors in the calculation of some of the Einstein coefficients in Table 5 and some plots in Figure 3. Due to the errors, the square-root section of the curves of growth of Fe xxvi Ka and Kb, and Ni xxviii Ka in Figure 3 were a few times underestimated. We correct Table 5 and re-plot Figure 3 together with the unaffected curves. The program to calculate the corrected curves of growth is available at http://www.hp.phys.titech.ac.jp/kotani/cog/index.html

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arXiv2005

Ionization States and Plasma Structures of Mixed-morphology SNRs Observed with ASCA

We present the results of a systematic study using ASCA of the ionization state for six ``mixed-morphology'' supernova emnants (MMSNRs): IC 443, W49B, W28, W44, 3C391, and Kes 27. MMSNRs show centrally filled thermal X-ray emission, which contrasts to shell-like radio morphology, a set of haracteristics at odds with the standard model of SNR evolution (e.g., the Sedov model). We have therefore studied the evolution of the MMSNRs from the ionization conditions inferred from the X-ray spectra, independent of X-ray morphology. We find highly ionized plasmas approaching ionization equilibrium in all the mmsnrs. The degree of ionization is systematically higher than the plasma usually seen in shell-like SNRs. Radial temperature gradients are also observed in five remnants, with cooler plasma toward the limb. In IC 443 and W49B, we find a plasma structure consistent with shell-like SNRs, suggesting that at least some MMSNRs have experienced similar evolution to shell-like SNRs. In addition to the results above, we have discovered an ``overionized'' ionization state in W49B, in addition to that previously found in IC 443. Thermal conduction can cause the hot interior plasma to become overionized by reducing the temperature and density gradients, leading to an interior density increase and temperature decrease. Therefore, we suggest that the ``center-filled'' X-ray morphology develops as the result of thermal conduction, and should arise in all SNRs. This is consistent with the results that MMSNRs are near collisional ionization equilibrium since the conduction timescale is roughly similar to the ionization timescale. Hence, we conclude that MMSNRs are those that have evolved over$\sim10^4$ yr. We call this phase as the ``conduction phase.''

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arXiv2003

An X-Ray Detection Possibility of Star-Formation-Bursting Proto-Elliptical Galaxies

A possibility to detect X-rays from star-formation burst activities in proto-elliptical galaxies is considered. The X-ray flux of an emission due to inverse Compton scattering of the cosmic microwave background (CMB) by high energy electrons accelerated in SNRs is shown to increase as z increases far beyond unity, since the local CMB flux largely increases in association with a z-increase. The flux is estimated for the case of a very high rate of type II supernovae at an initial star formation burst of a proto-elliptical galaxy and is found to be detectable with a future large X-ray telescope such as intended in the XEUS mission.

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arXiv2002

Origin of the "Disk-Line" Feature in the X-Ray Energy Spectrum of a Seyfert Galaxy, NGC4151

We have studied the origin of the broad and skewed feature at 4.5-7.5 keV in the energy spectra of NGC4151 using the ASCA and RXTE data. The feature consists of a narrow peak at 6.4 keV and a broad wing extended between 4.5-7.5 keV. An analysis of the long-term variations revealed that the feature became variable only on a time scale longer than 1.5x10^6 s. Through a comparison with the continuum variabilities, we found that the emission region of the excess flux at 4.5-7.5 keV has an extent of 10^17 cm. The broad and skewed feature at 4.5-7.5 keV may be explained by the so-called ``disk-line'' model. If so, the size of the line-emitting region, 10^17 cm, should be equal to several or ten-times the Schwarzschild radius of the central black hole. This results in a black hole mass of 10^11 solar mass, which may be too large for NGC4151. We propose an alternative explanation for the broad and skewed feature, i.e. a ``reflection'' model, which can also reproduce the overall energy spectra very well. In this model, cold matter with a sufficiently large column density is irradiated by X-rays to produce a reflected continuum, which constitutes the broad wing of the feature, and narrow fluorescent lines. The equivalent width of the iron fluorescent line (~2 keV) and the upper limit of its width (sigma < 92 eV) are also consistent with this model. From these results and considerations, we conclude that the ``disk-line'' model has difficulty to explain the spectral variations of NGC4151, and the reflection model is more plausible.

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