X-Ray Observations of the W51 Complex with Suzaku

We present a detailed analysis of the X-ray emission from the middle-aged supernova remnant W51C and star-forming region W51B with Suzaku. The soft X-ray emission from W51C is well represented by an optically thin thermal plasma in the non-equilibrium ionization state with a temperature of $\sim$0.7 keV. The elemental abundance of Mg is significantly higher than the solar value. We find no significant feature of an over-ionized plasma in W51C. The hard X-ray emission is spatially coincident with the molecular clouds associated with W51B, overlapping with W51C. The spectrum is represented by an optically thin thermal plasma with a temperature of $\sim$5 keV or a powerlaw model with a photon index of $\sim$2.2. The emission probably has diffuse nature since its luminosity of 1$\times10^{34}$ erg s$^{-1}$ in the 0.5-10 keV band cannot be explained by the emission from point sources in this region. We discuss the possibility that the hard X-ray emission comes from stellar winds of OB stars in W51B or accelerated particles in W51C.Comment: 11 pages, 5 figures, accepted for publication in PAS

Tracking the Complex Absorption in NGC 2110 with Two Suzaku Observations

We present spectral analysis of two Suzaku observations of the Seyfert 2 galaxy, NGC 2110. This source has been known to show complex, variable absorption which we study in depth by analyzing these two observations set seven years apart and by comparing to previously analyzed observations with the XMM-Newton and Chandra observatories. We find that there is a relatively stable, full-covering absorber with a column density of ~3$\times 10 ^{22}$ cm$^{-2}$, with an additional patchy absorber that is likely variable in both column density and covering fraction over timescales of years, consistent with clouds in a patchy torus or in the broad line region. We model a soft emission line complex, likely arising from ionized plasma and consistent with previous studies. We find no evidence for reflection from an accretion disk in this source with no contribution from relativistically broadened Fe Ka line emission nor from a Compton reflection hump.Comment: Accepted to ApJ: March, 201

The Suzaku Observation of the Nucleus of the Radio-Loud Active Galaxy Centaurus A: Constraints on Abundances of the Accreting Material

A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3 to 250 keV. The net exposure times after screening were: 70 ks per X-ray Imaging Spectrometer (XIS) camera, 60.8 ks for the Hard X-ray Detector (HXD) PIN, and 17.1 ks for the HXD-GSO. The hard X-rays are fit by two power-laws of the same slope, absorbed by columns of 1.5 and 7 * 10^{23} cm^{-2} respectively. The spectrum is consistent with previous suggestions that the power-law components are X-ray emission from the sub-pc VLBI jet and from Bondi accretion at the core, but it is also consistent with a partial covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature VAPEC model, plus a third power-law component to account for scattered nuclear emission, jet emission, and emission from X-ray Binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca and Ni are detected. The Fe K alpha line width yields a 200 light-day lower limit on the distance from the black hole to the line-emitting gas. Fe, Ca, and S K-shell absorption edges are detected. Elemental abundances are constrained via absorption edge depths and strengths of the fluorescent and diffuse plasma emission lines. The high metallicity ([Fe/H]=+0.1) of the circumnuclear material suggests that it could not have originated in the relatively metal-poor outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.Comment: Accepted for publication to ApJ. 22 pages, 11 figures (3 color). Uses emulateapj5.sty. Grammatical errors corrected; some references update

Suzaku wide-band observations of SN 1006

We report on the wide band spectra of SN 1006 as observed by Suzaku. Thermal and nonthermal emission are successfully resolved thanks to the excellent spectral response of Suzaku's X-ray CCD XIS. The nonthermal emission cannot be reproduced by a simple power-law model but needs a roll-off at 5.7$\times 10^{16}$ Hz = 0.23 keV. The roll-off frequency is significantly higher in the northeastern rim than in the southwestern rim. We also have placed the most stringent upper limit of the flux above 10 keV using the Hard X-ray Detector.Comment: 16 pages, 8 figures, PASJ, in pres

Suzaku Observations of the Non-thermal Supernova Remnant HESS J1731-347

A detailed analysis of the nonthermal X-ray emission from the North-Western and Southern parts of the supernova remnant (SNR) HESS J1731$-$347 with {\it Suzaku} is presented. The shell portions covered by the observations emit hard and line-less X-rays. The spectrum can be reproduced by a simple absorbed power-law model with a photon index $\Gamma$ of 1.8-2.7 and an absorption column density $N_{\rm H}$ of (1.0-2.1)$\times 10^{22}$ cm$^{-2}$. These quantities change significantly from region to region; the North-Western part of the SNR has the hardest and most absorbed spectrum. The Western part of the X-ray shell has a smaller curvature than North-Western and Southern shell segments. A comparison of the X-ray morphology to the Very High Energy (VHE) gamma-ray and radio images was performed. The efficiency of electron acceleration and emission mechanism in each portion of the shell are discussed. Thermal X-ray emission from the SNR was searched for but could not be detected at a significant level.Comment: 23 pages, 28 figures, ApJ, in pres