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

Suzaku Observations of the Supernova Remnant N23 in the Large Magellanic Cloud

X-ray emission from the supernova remnant N23 in the Large Magellanic Cloud (LMC) is studied using the X-ray Imaging Spectrometer (XIS) onboard Suzaku. Thanks to superior energy resolution of the XIS in the soft X-ray band, we resolved H-like and He-like Oxygen K\alpha emission lines from N23 with unprecedentedly high quality, and as a result, identified a new optically thin thermal emission component with a temperature ~0.2 keV, as well as that with a temperature of ~0.5-0.7 keV previously known. This alters the estimate of the ionization timescale net from ~10^{10-11} cm^-3s to >~10^{12} cm^{-3}s. Under the assumption that N23 is still in the Sedov phase, its age evaluated from the newly discovered low temperature component is ~8000 yr, although it is possible that N23 has already moved into the radiative phase. The abundances of the heavy elements are found to be roughly consistent with those of the LMC average, which indicates that the origin of the X-ray emission of N23 is swept-up ambient material, as expected from its ionization timescale.Comment: 7 pages, 5 figures, accepted for publication in PAS

Deep X-Ray Observations of Supernova Remnants G359.1-0.5 and G359.0-0.9 with ASCA

We present the results of deep ASCA observations of two shell-like radio supernova remnants (SNRs) located in the direction to the Galactic center (GC) region. Unlike the radio morphology, G359.1-0.5 shows center-filled X-rays with prominent K-alpha lines of He-like silicon and H-like sulfur. The plasma requires at least two temperature components: a silicon-dominated cool plasma of 0.6keV temperature and a sulfur-dominated higher temperature plasma of 4.4keV. Because the absorption column is ~ 6x10^22 H cm^-2, this SNR would be near to the GC. The spherical plasma is attributable to supernova ejecta with the total mass of Si and S being about 0.1 solar mass and 0.3 solar mass, respectively. X-rays from G359.0-0.9 trace the partial shell structure of the radio emission. The spectrum is well fitted to a single-temperature plasma of 0.4keV with a non-solar abundance of magnesium or iron. Because the absorption column is not very large, ~ 1.8x10^22 H cm^-2, G359.0-0.9 would be in front of the GC region. The total supernova energy, interstellar density near to the X-ray emitting shell and age of the SNR are estimated to be 1.2x10^51erg, 0.5cm^-3, and 1.8x10^4yr, respectively. We also discuss possible implications on the origin of the large-scale hot plasma surrounding the GC.Comment: 8 pages, 7 postscript figures, uses PASJ95.sty and PASJadd.sty; accepted for publication in PASJ 52 April 2000; changed one of figure

The many sides of RCW 86: a type Ia supernova remnant evolving in its progenitor's wind bubble

We present the results of a detailed investigation of the Galactic supernova remnant RCW 86 using the XMM-Newton X-ray telescope. RCW 86 is the probable remnant of SN 185 A.D, a supernova that likely exploded inside a wind-blown cavity. We use the XMM-Newton Reflection Grating Spectrometer (RGS) to derive precise temperatures and ionization ages of the plasma, which are an indication of the interaction history of the remnant with the presumed cavity. We find that the spectra are well fitted by two non-equilibrium ionization models, which enables us to constrain the properties of the ejecta and interstellar matter plasma. Furthermore, we performed a principal component analysis on EPIC MOS and pn data to find regions with particular spectral properties. We present evidence that the shocked ejecta, emitting Fe-K and Si line emission, are confined to a shell of approximately 2 pc width with an oblate spheroidal morphology. Using detailed hydrodynamical simulations, we show that general dynamical and emission properties at different portions of the remnant can be well-reproduced by a type Ia supernova that exploded in a non-spherically symmetric wind-blown cavity. We also show that this cavity can be created using general wind properties for a single degenerate system. Our data and simulations provide further evidence that RCW 86 is indeed the remnant of SN 185, and is the likely result of a type Ia explosion of single degenerate origin.Comment: Accepted for publication in MNRAS. 16 pages, 13 figure

Chandra Observations of a Non-Thermal Supernova Remnant Candidate AX J1843.8-0352 and its Surroundings

We present the Chandra results of AX J1843.8-0352, a supernova remnant (SNR) recently identified with ASCA. Chandra spatially resolved two components from this SNR: non-thermal and thermal ones. The morphology of the non-thermal component is clumpy and elliptical, elongated from the north to the south with a mean diameter of about 9 arcmin. The spectrum is fitted with a power-law model of photon index 2.1 and the east rim is associated with the non-thermal radio sources C and F (Helfand et al. 1989). Therefore the non-thermal component is probably synchrotron X-rays by energetic electrons accelerated at the shell of the SNR. The thermal component is the brightest clump located within the non-thermal component and shows a spectrum of a thin plasma of about 0.7 keV temperature. Notable discovery is its peculiar morphology; a head of 50 arcsec x 30 arcsec size near the south-east rim of the SNR and a 30 arcsec-long ``jet'' pointing to the southwest. Although this emission is associated with the west part of the radio source F, the absorption is twice larger than that of the non-thermal X-rays, or the bulk of the SNR emission. Therefore, it is unclear whether this peculiar plasma is a thermal component associated with AX J1843.8-0352, a Galactic source located in the far side of our Galaxy, or an extragalactic source.Comment: 19 pages, 5 figures; to appear in Ap