We report the global distribution of the intensities of the K-shell lines from the He-like and H-like ions of S, Ar, Ca and Fe along the Galactic plane. From the profiles, we clearly separate the Galactic center X-ray emission (GCXE) and the Galactic
ridge X-ray emission (GRXE). The intensity profiles of the He-like K$alpha$ lines of S, Ar, Ca and Fe along the Galactic plane are approximately similar with each other, while not for the H-like Ly$alpha$ lines. In particular, the profiles of H-like Ly$alpha$ of S and Fe show remarkable contrast; a large excess of Fe and almost no excess of S lines in the GCXE compared to the GRXE. Although the prominent K-shell lines are represented by $sim$1 keV and $sim$7 keV temperature plasmas, these two temperatures are not equal between the GCXE and GRXE. In fact, the spectral analysis of the GCXE and GRXE revealed that the $sim$1 keV plasma in the GCXE has lower temperature than that in the GRXE, and vice versa for the $sim$7 keV plasma.
Prominent K-shell emission lines of neutral iron (hereafter, FeI-K) and hard-continuum X-rays were found from molecular clouds (MCs) in the Sagittarius B (Sgr B) region with the two separate Suzaku observations in 2005 and 2009. The X-ray flux of FeI
-K decreased in correlation to the hard-continuum flux by factor of 0.4-0.5 in 4 years, which is nearly equal to the light-travelling across the MCs. The rapid and correlated time-variability, the equivalent width of FeI-K, and the K-edge absorption depth of FeI are consistently explained by X-ray echoes due to the fluorescent and Thomson-scattering of an X-ray flare from an external source. The required flux of the X-ray flare depends on the distance to the MCs and the duration time. The flux, even in the minimum case, is larger than those of the brightest Galactic X-ray sources. Based on these facts, we conclude that the super-massive black hole, Sgr A*, exhibited a big-flare about a few hundred years ago and the luminosity of higher than 4x10^39 erg s^{-1}. The X-ray echo from Sgr B, located at a few hundred light-years from Sgr A*, now arrived at the Earth.
We have surveyed spatial profiles of the Fe K$alpha$ lines in the Galactic center diffuse X-rays (GCDX), including the transient region from the GCDX to the Galactic ridge X-ray emission (GRXE), with the Suzaku satellite. We resolved Fe K$alpha$ line
complex into three lines of Fe emissiontype{I}, Fe emissiontype{XXV} and Fe emissiontype{XXVI} K$alpha$, and obtained their spatial intensity profiles with the resolution of $sim timeform{0D.1}$. We compared the Fe emissiontype{XXV} K$alpha$ profile with a stellar mass distribution (SMD) model made from near infrared observations. The intensity profile of Fe emissiontype{XXV} K$alpha$ is nicely fitted with the SMD model in the GRXE region, while that in the GCDX region shows $3.8pm0.3$ $(timeform{0D.2}<|l|<timeform{1D.5})$ or $19pm6$ $(|l|<timeform{0D.2})$ times excess over the best-fit SMD model in the GRXE region. Thus Fe emissiontype{XXV} K$alpha$ in the GCDX is hardly explained by the same origin of the GRXE. In the case of point source origin, a new population with the extremely strong Fe emissiontype{XXV} K$alpha$ line is required. An alternative possibility is that the majority of the GCDX is truly diffuse optically thin thermal plasma.
We report the Suzaku observation of 1E 1740.7-2942, a black hole candidate called the Great Annihilator (GA). The high-quality spectrum of Suzaku provides the severest constraints on the parameters of the GA. Two clumpy structures are found around th
e GA in the line images of FeI Kalpha at 6.4 keV and SXV Kalpha at 2.45 keV. One clump named M359.23-0.04 exhibits the 6.4-keV line with an equivalent width of ~ 1.2 keV, and is associated with a molecular cloud in the radio CS(J=1-0) map. Thus the 6.4-keV line from M359.23-0.04 is likely due to X-ray fluorescence irradiated by an external X-ray source. The irradiating X-rays would be either the past flare of Sagittarius A* or the bright nearby source, the GA. The other clump named G359.12-0.05 is associated with the radio supernova remnant candidate G359.07-0.02. We therefore propose that G359.12-0.05 is an X-ray counterpart of G359.07-0.02. G359.12-0.05 has a thin thermal plasma spectrum with a temperature of kT ~ 0.9 keV. The plasma parameters of G359.12-0.05 are consistent with those of a single supernova remnant in the Galactic center region.
We present the Suzaku results on a new candidate of a supernova remnant (SNR) in the Sagittarius C region. We detected diffuse X-rays of an elliptical shape (G359.41-0.12) and a chimney-like structure (the Chimney), both of which were fitted with a t
hin thermal the model of kBT ~1 keV temperature. The absorption columns are same between these two structures, indicating that both are located at the same distance in the same line of sight. The narrow band image and one-dimensional profile of S XV Kalpha at 2.45 keV show that the Chimney is emanating from G359.41-0.12. Therefore, these two sources are physically connected with each other. The sum of the thermal energies of the Chimney and G359.41-0.12 is estimated to be 1.4x10^50 erg, typical for a galactic SNR. G359.41-0.12 is likely to be a new SNR candidate and the Chimney is an associated outflow.
This paper reports on the first results of the Suzaku observation in the Sgr C region. We detected four diffuse clumps with strong line emission at 6.4keV, Ka from neutral or low-ionized Fe. One of them, M359.38-0.00, is newly discovered with Suzaku.
The X-ray spectra of the two bright clumps, M359.43-0.07 and M359.47-0.15, after subtracting the Galactic center diffuse X-ray emission (GCDX), exhibit strong Ka line from FeI with large equivalent widths (EWs) of 2.0-2.2keV and clear Kb of FeI. The GCDX in the Sgr C region is composed of the 6.4keV- and 6.7keV-associated components. These are phenomenologically decomposed by taking relations between EWs of the 6.4keV and 6.7keV lines. Then the former EWs against the associated continuum in the bright clump regions are estimated to be 2.4(+2.3_-0.7)keV. Since the two different approaches give similar large EWs of 2keV, we strongly suggest that the 6.4keV clumps in the Sgr C region are due to X-ray reflection/fluorescence (the X-ray reflection nebulae).
SAX J1748.2$-$2808 is a unique X-ray object with a flat spectrum and strong emission lines at 6.4--7.0 keV. The Suzaku satellite resolved the emission lines into 3 K-shell lines from neutral and highly ionized irons. A clear coherent pulsation with a
period of 593-sec was found from the Suzaku and XMM-Newton archives. These facts favor that SAX J1748.2$-$2808 isan intermediate polar, a subclass of magnetized white dwarf binary (cataclysmic variable: CV). This paper reports on details of the findings and discusses the origin of this source.
We made a 100 ks observation of the Sagittarius (Sgr) B1 region at (l, b) = (0.5, -0.1) near to the Galactic center (GC) with the Suzaku/XIS. Emission lines of S XV, Fe I, Fe XXV, and Fe XXVI were clearly detected in the spectrum. We found that the F
e XXV and Fe XXVI line emissions smoothly distribute over the Sgr B1 and B2 regions connecting from the GC. This result suggests that the GC hot plasma extends at least up to the Sgr B region with a constant temperature. There are two diffuse X-ray sources in the observed region. One of the two (G0.42-0.04) is newly discovered, and exhibits a strong S XV Ka emission line, suggesting a candidate for a supernova remnant located in the GC region. The other one (M0.51-0.10), having a prominent Fe I Ka emission line and a strongly absorbed continuum, is likely to be an X-ray reflection nebula. There is no near source bright enough to irradiate M0.51-0.10. However, the Fe I Ka emission can be explained if Sgr A* was ~ 10^6 times brighter 300 years ago, the light travel time for 100 pc to M0.51-0.10, than it is at present.
