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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.
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The detection of photons above 10 keV through MeV and GeV energies is challenging due to the penetrating nature of the radiation, which can require large detector volumes, resulting in correspondingly high background. In this energy range, most detectors in space are either scintillators or solid-state detectors. The choice of detector technology depends on the energy range of interest, expected levels of signal and background, required energy and spatial resolution, particle environment on orbit, and other factors. This section covers the materials and configurations commonly used from 10 keV to > 1 GeV.
X-radiation from energetic electrons is the prime diagnostic of flare-accelerated electrons. The observed X-ray flux (and polarization state) is fundamentally a convolution of the cross-section for the hard X-ray emission process(es) in question with the electron distribution function, which is in turn a function of energy, direction, spatial location and time. To address the problems of particle propagation and acceleration one needs to infer as much information as possible on this electron distribution function, through a deconvolution of this fundamental relationship. This review presents recent progress toward this goal using spectroscopic, imaging and polarization measurements, primarily from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Previous conclusions regarding the energy, angular (pitch angle) and spatial distributions of energetic electrons in solar flares are critically reviewed. We discuss the role and the observational evidence of several radiation processes: free-free electron-ion, free-free electron-electron, free-bound electron-ion bremsstrahlung, photoelectric absorption and Compton back-scatter (albedo), using both spectroscopic and imaging techniques. This unprecedented quality of data allows for the first time inference of the angular distributions of the X-ray-emitting electrons using albedo, improved model-independent inference of electron energy spectra and emission measures of thermal plasma. Moreover, imaging spectroscopy has revealed hitherto unknown details of solar flare morphology and detailed spectroscopy of coronal, footpoint and extended sources in flaring regions. Additional attempts to measure hard X-ray polarization were not sufficient to put constraints on the degree of anisotropy of electrons, but point to the importance of obtaining good quality polarization data.
In this paper the current status of high-energy research on the hard X-ray characteristics of the persistent emission from magnetars is reviewed. Focus is put on recent intriguing results for 1RXS J1708-40, from phase resolved spectral analysis over a 2 decades wide energy band (~3-300 keV) combining contemporaneous RXTE, XMM and INTEGRAL data. For 1E 1841-045 and SGR 1806-10 we also present updated results. The perspective for future MAXI observations for this source class is also addressed.
The ISM evolution of elliptical galaxies experiencing feedback from accretion onto a central black hole was studied recently with high-resolution 1D hydrodynamical simulations including radiative heating and pressure effects, a RIAF-like radiative efficiency, mechanical input from AGN winds, and accretion-driven starbursts. Here we focus on the observational properties of the models in the X-ray band (nuclear luminosity; hot ISM luminosity and temperature; temperature and brightness profiles during quiescence and during outbursts). The nuclear bursts last for ~10^7 yr, with a duty-cycle of a few X (10^-3-10^-2); the present epoch bolometric nuclear emission is very sub-Eddington. The ISM thermal luminosity lx oscillates in phase with the nuclear one; this helps reproduce statistically the observed large lx variation. In quiescence the temperature profile has a negative gradient; thanks to past outbursts, the brightness profile lacks the steep shape typical of inflowing models. Outbursts produce disturbances in these profiles. Most significantly, a hot bubble from shocked hot gas is inflated at the galaxy center; the bubble would be conical in shape, and show radio emission. The ISM resumes a smooth appearance on a time-scale of ~200 Myr; the duty-cycle of perturbances in the ISM is of the order of 5-10%. From the present analysis, additional input physics is important in the ISM-black hole coevolution, to fully account for the properties of real galaxies, as a confining external medium and a jet. The jet will reduce further the mass available for accretion (and then the Eddington ratio $l$), and may help, together with an external pressure, to produce flat or positive temperature gradient profiles (observed in high density environments). Alternatively, $l$ can be reduced if the switch from high to low radiative efficiency takes place at a larger $l$ than routinely assumed.
Using the latest 70 month Swift-BAT catalog we examined hard X-ray selected Seyfert I galaxies which are relatively little known and little studied, and yet potentially promising to test the ionized relativistic reflection model. From this list we chose 13 sources which have been observed by XMM-Newton for less than 20 ks, in order to explore the broad band soft to hard X-ray properties with the analysis of combined XMM-Newton and Swift data. Out of these we found seven sources which exhibit potentially promising features of the relativistic disc reflection, such as a strong soft excess, a large Compton hump and/or a broadened Fe line. Longer observations of four of these sources with the currently operating satellite missions, such as Suzaku, XMM-Newton and NuStar and two others by such future missions as ASTRO-H, will be invaluable, in order to better understand the relativistic disc reflection closest to the central black hole and constrain such important effects of strong gravity as the black hole spin.
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