Expected Hard X-Ray and Soft Gamma-Ray from Supernovae

High energy emissions from supernovae (SNe), originated from newly formed radioactive species, provide direct evidence of nucleosynthesis at SN explosions. However, observational difficulties in the MeV range have so far allowed the signal detected only from the extremely nearby core-collapse SN 1987A. No solid detection has been reported for thermonuclear SNe Ia, despite the importance of the direct confirmation of the formation of 56Ni, which is believed to be a key ingredient in their nature as distance indicators. In this paper, we show that the new generation hard X-ray and soft gamma-ray instruments, on board Astro-H and NuStar, are capable of detecting the signal, at least at a pace of once in a few years, opening up this new window for studying SN explosion and nucleosynthesis.Comment: 4 pages, 3 figures and 1 table. Invited talk at Frascati Workshop 2013 on Multifrequency Behaviour of High Energy Cosmic Sources (Palermo, 27 May - 1 June, 2013). To be published in the International Journal Acta Polytechnica (CTU

X-ray Measurements of the Particle Acceleration Properties at Inward Shocks in Cassiopeia A

We present new evidence that the bright non-thermal X-ray emission features in the interior of the Cassiopeia A supernova remnant (SNR) are caused by inward moving shocks based on Chandra and NuSTAR observations. Several bright inward-moving filaments were identified using monitoring data taken by Chandra in 2000-2014. These inward-moving shock locations are nearly coincident with hard X-ray (15-40 keV) hot spots seen by NuSTAR. From proper motion measurements, the transverse velocities were estimated to be in the range $\sim$2,100-3,800 km s$^{-1}$ for a distance of 3.4 kpc. The shock velocities in the frame of the expanding ejecta reach values of $\sim$5,100-8,700 km s$^{-1}$, slightly higher than the typical speed of the forward shock. Additionally, we find flux variations (both increasing and decreasing) on timescales of a few years in some of the inward-moving shock filaments. The rapid variability timescales are consistent with an amplified magnetic field of $B \sim$ 0.5-1 mG. The high speed and low photon cut-off energy of the inward-moving shocks are shown to imply a particle diffusion coefficient that departs from the Bohm regime ($k_0 = D_0/D_{\rm 0,Bohm} \sim$ 3-8) for the few simple physical configurations we consider in this study. The maximum electron energy at these shocks is estimated to be $\sim$8-11 TeV, smaller than the values of $\sim$15-34 TeV inferred for the forward shock. Cassiopeia A is dynamically too young for its reverse shock to appear to be moving inward in the observer frame. We propose instead that the inward-moving shocks are a consequence of the forward shock encountering a density jump of $\gtrsim$ 5-8 in the surrounding material.Comment: 16 pages, 8 figures, accepted for publication in Ap

Origin of Thermal and Non-Thermal Hard X-ray Emission from the Galactic Center

We analyse new results of Chandra and Suzaku which found a flux of hard X-ray emission from the compact region around Sgr A$^\ast$ (r ~ 100 pc). We suppose that this emission is generated by accretion processes onto the central supermassive blackhole when an unbounded part of captured stars obtains an additional momentum. As a result a flux of subrelativistic protons is generated near the Galactic center which heats the background plasma up to temperatures about 6-10 keV and produces by inverse bremsstrahlung a flux of non-thermal X-ray emission in the energy range above 10 keV.Comment: to be published in PASJ, v.61, No.5, 200

Suzaku Detection of Extended/Diffuse Hard X-Ray Emission from the Galactic Center

Five on-plane regions within +/- 0.8deg of the Galactic center were observed with the Hard X-ray Detector (HXD) and the X-ray Imaging Spectrometer (XIS) onboard Suzaku. From all regions, significant hard X-ray emission was detected with HXD-PIN up to 40 keV, in addition to the extended plasma emission which is dominant in the XIS band. The hard X-ray signals are inferred to come primarily from a spatially extended source, rather than from a small number of bright discrete objects. Contributions to the HXD data from catalogued X-ray sources, typically brighter than 1 mCrab, were estimated and removed using information from Suzaku and other satellites. Even after this removal, the hard X-ray signals remained significant, exhibiting a typical 12--40 keV surface brightness of 4E-10 erg cm-2 s-1 deg-2 and power-law-like spectra with a photon index of 1.8. Combined fittings to the XIS and HXD-PIN spectra confirm that a separate hard tail component is superposed onto the hot thermal emission, confirming a previous report based on the XIS data. Over the 5--40 keV band, the hard tail is spectrally approximated by a power law of photon index ~2, but better by those with somewhat convex shapes. Possible origins of the extended hard X-ray emission are discussed.Comment: 13 pages, 18 figure

Comparison of muscle quality and functional capacity between Japanese and Brazilian older individuals

Muscle quality is well-known to decrease with aging and is a risk factor for metabolic abnormalities. However, there is a lack of information on race-associated differences in muscle quality and other neuromuscular features related to functional performance. This study aimed to compare muscle quality, function, and morphological characteristics in Japanese and Brazilian older individuals. Eighty-four participants aged 65–87 years were enrolled in the study (42 Japanese: 23 men, 19 women, mean age 70.4 years; 42 Brazilians: 23 men, 19 women, mean age 70.8 years). Echo intensity (EI) and muscle thickness (MT) of the quadriceps femoris were measured using B-mode ultrasonography. A stepwise multiple linear regression analysis with EI as a dependent variable revealed that MT was a significant variable for Japanese participants (R2 = 0.424, P = 0.001), while MT and subcutaneous adipose tissue (SCAT) thickness were significant variables for Brazilian participants (R2 = 0.490, P = 0.001). A second stepwise multiple linear regression analysis was performed after excluding MT and SCAT thickness from the independent variables. Sex and age for Japanese participants (R2 = 0.381, P = 0.001) and lean body mass and body mass index for Brazilian participants (R2 = 0.385, P = 0.001) were identified as significant independent variables. The present results suggest that MT is closely correlated with muscle quality in Japanese and Brazilian older individuals. Increases in muscle size may induce decreases in intramuscular adipose tissue and/or connective tissues, which are beneficial for reducing the risks of metabolic impairments in Japanese and Brazilian older individuals