Measuring the Broad-band X-Ray Spectrum from 400 eV to 40 keV in the Southwest Part of the Supernova Remnant RX J1713.7-3946

We report on results from Suzaku broadband X-ray observations of the southwest part of the Galactic supernova remnant (SNR) RX J1713.7-3946 with an energy coverage of 0.4-40 keV. The X-ray spectrum, presumably of synchrotron origin, is known to be completely lineless, making this SNR ideally suited for a detailed study of the X-ray spectral shape formed through efficient particle acceleration at high speed shocks. With a sensitive hard X-ray measurement from the HXD PIN on board Suzaku, we determine the hard X-ray spectrum in the 12--40 keV range to be described by a power law with photon index Gamma = 3.2+/- 0.2, significantly steeper than the soft X-ray index of Gamma = 2.4+/- 0.05 measured previously with ASCA and other missions. We find that a simple power law fails to describe the full spectral range of 0.4-40 keV and instead a power-law with an exponential cutoff with hard index Gamma = 1.50+/- 0.09 and high-energy cutoff epsilon_c = 1.2+/- 0.3 keV formally provides an excellent fit over the full bandpass. If we use the so-called SRCUT model, as an alternative model, it gives the best-fit rolloff energy of epsilon_{roll} = 0.95+/- 0.04 keV. Together with the TeV gamma-ray spectrum ranging from 0.3 to 100 TeV obtained recently by HESS observations, our Suzaku observations of RX J1713.7-3946 provide stringent constraints on the highest energy particles accelerated in a supernova shock.Comment: 11 pages, 11 figures, accepted for publication in Publications of the Astronomical Society of Japan (PASJ

Greenland Ice Sheet Dynamics and Glacial Earthquake Activities

第2回極域科学シンポジウム　共通セッション「大気-海洋-雪氷-固体地球の相互作用」 11月15日（火） 統計数理研究所 3階リフレッシュフロ

ICE-S seismic station in the Greenland Ice Sheet Monitoring Network

第2回極域科学シンポジウム/第31回極域地学シンポジウム 11月16日（水） 国立国語研究

Japanese contribution to the GreenLand Ice Sheet monitoring Network (GLISN)

第3回極域科学シンポジウム/特別セッション「これからの北極研究」11月28日（水） 国立極地研究所 2階大会議

Ambient noise cross-correlation analysis using broadband continuous seismic waveform data from the Greenland ice sheet

第6回極域科学シンポジウム[OG] 地圏11月16日（月）　国立極地研究所３階セミナー

Outburst of LS V+44 17 Observed by MAXI and RXTE, and Discovery of a Dip Structure in the Pulse Profile

We report on the first observation of an X-ray outburst of a Be/X-ray binary pulsar LS V +44 17/RX J0440.9+4431, and the discovery of an absorption dip structure in the pulse profile. An outburst of this source was discovered by MAXI GSC in 2010 April. It was the first detection of the transient activity of LS V +44 17 since the source was identified as a Be/X-ray binary in 1997. From the data of the follow-up RXTE observation near the peak of the outburst, we found a narrow dip structure in its pulse profile which was clearer in the lower energy bands. The pulse-phase-averaged energy spectra in the 3$-$100 keV band can be fitted with a continuum model containing a power-law function with an exponential cutoff and a blackbody component, which are modified at low energy by an absorption component. A weak iron K$\alpha$ emission line is also detected in the spectra. From the pulse-phase-resolved spectroscopy we found that the absorption column density at the dip phase was much higher than those in the other phases. The dip was not seen in the subsequent RXTE observations at lower flux levels. These results suggest that the dip in the pulse profile originates from the eclipse of the radiation from the neutron star by the accretion column.Comment: 18 pages, 7 figures, accepted for publication in PAS

A Spectral Study of the Black Hole Candidate XTE J1752-223 in the High/Soft State with MAXI, Suzaku and Swift

We report on the X-ray spectral analysis of the black hole candidate XTE\ J1752--223 in the 2009--2010 outburst, utilizing data obtained with the MAXI/Gas Slit Camera (GSC), the Swift/XRT, and Suzaku, which work complementarily. As already reported by Nakahira et al. (2010) MAXI monitored the source continuously throughout the entire outburst for about eight months. All the MAXI/GSC energy spectra in the high/soft state lasting for 2 months are well represented by a multi-color disk plus power-law model. The innermost disk temperature changed from $\sim$0.7 keV to $\sim$0.4 keV and the disk flux decreased by an order of magnitude. Nevertheless, the innermost radius is constant at $\sim$41 $D_{3.5}(\cos{\it i})^{-1/2}$ km, where $D_{3.5}$ is the source distance in units of 3.5 kpc and $i$ the inclination. The multi-color disk parameters obtained with the MAXI/GSC are consistent with those with the Swift/XRT and Suzaku. The Suzaku data also suggests a possibility that the disk emission is slightly Comptonized, which could account for broad iron-K features reported previously. Assuming that the obtained innermost radius represents the innermost stable circular orbit for a non-rotating black hole, we estimate the mass of the black hole to be 5.51$\pm$0.28 $M_{\odot}$ $D_{3.5}(\cos{\it i})^{-1/2}$, where the correction for the stress-free inner boundary condition and color hardening factor of 1.7 are taken into account. If the inclination is less than 49$^{\circ}$ as suggested from the radio monitoring of transient jets and the soft-to-hard transition in 2010 April occurred at 1--4% of Eddignton luminosity, the fitting of the Suzaku spectra with a relativistic accretion-disk model derives constraints on the mass and the distance to be 3.1--55 $M_{\odot}$ and 2.3--22 {\rm kpc}, respectively. This confirms that the compact object in XTE J1752--223 is a black hole.Comment: 12 pages including 7 figures and 4 tables, accepted for publication in PAS