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Register a new userSuzaku Spectroscopy of an X-Ray Reflection Nebula and a New Supernova Remnant Candidate in the Sgr B1 Region
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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 Fe 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.
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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 thin 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.
We present evidence supporting a SNR origin for the radio source G337.2+0.1, which was discovered along the line of sight to the Norma spiral arm in the MOST 843-MHz radio survey. The radio source is spatially superposed to the unidentified ASCA source AX J1635.9-4719. An analysis of this latter source reveals that its X-ray spectrum, extended nature, and non-variable flux are consistent with what is expected for a SNR. In addition, we have used HI-line observations of the region to look for any effect of the presumed remnant on the ISM. We have found a well-defined minimum centered at the position of the radio source in the velocity range of ~ -25 to -19 km/s. This feature appears as a sharp absorption dip in the spectrum that might be produced when the continuum emission from the SNR candidate is absorbed by foreground gas. Hence we have used it to constrain the distance to the source, which seems to be a young (age ~ a few 10^3 yr) and distant (d ~ 14 kpc) SNR. G337.2+0.1 and AX J1635.9-4719 would be the radio/X-ray manifestations of this remnant.
We present an ASCA discovery of diffuse hard X-ray emission from the Sgr C complex with its peak in the vicinity of the molecular cloud core. The X-ray spectrum is characterized by a strong 6.4-keV line and large absorption. These properties suggest that Sgr C is a new X-ray reflection nebula which emits fluorescent and scattered X-rays via irradiation from an external X-ray source. We found no adequately bright source in the immediate Sgr C vicinity to fully account for the fluorescence. The irradiating source may be the Galactic nucleus Sgr A*, which was brighter in the past than it is now as is suggested from observations of the first X-ray reflection nebula Sgr B2.
We present an X-ray study of the mixed-morphology supernova remnant CTB 1 (G116.9+0.2) observed with Suzaku. The 0.6-2.0 keV spectra in the northeast breakout region of CTB 1 are well represented by a collisional ionization-equilibrium plasma model with an electron temperature of ~ 0.3 keV, whereas those in the southwest inner-shell region can be reproduced by a recombining plasma model with an electron temperature of ~ 0.2 keV, an initial ionization temperature of ~ 3 keV, and an ionization parameter of ~ 9 $times$ 10$^{11}$ cm$^{-3}$s. This is the first detection of the recombining plasma in CTB 1. The electron temperature in the inner-shell region decreases outwards, which implies that the recombining plasma is likely formed by the thermal conduction via interaction with the surrounding cold interstellar medium. The Ne abundance is almost uniform in the observed regions whereas Fe is more abundant toward the southwest of the remnant, suggesting an asymmetric ejecta distribution. We also detect a hard tail above the 2 keV band that is fitted with a power-law function with a photon index of 2-3. The flux of the hard tail in the 2-10 keV band is ~ 5 $times$ 10$^{-13}$ erg cm$^{-2}$ s$^{-1}$ and is peaked at the center of CTB 1. Its origin is unclear but one possibility is a putative pulsar wind nebula associated with CTB 1.
A compact complex of line emission filaments in the galactic plane has the appearance of those expected of an evolved supernova remnant though non-thermal radio and X-ray emission have not yet been detected. This optical emission line region has now been observed with deep imagery and both low and high-dispersion spectroscopy. Diagnostic diagrams of the line intensities from the present spectra and the new kinematical observations both point to a supernova origin. However, several features of the nebular complex still require an explanation within this interpretation.
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