No abstract

High-sensitivity wide-band X-ray spectroscopy is the key feature of the Suzaku X-ray observatory, launched on 2005 July 10. This paper summarizes the spacecraft, in-orbit performance, operations, and data processing that are related to observations. The scientific instruments, the high-throughput X-ray telescopes, X-ray CCD cameras, non-imaging hard X-ray detector are also described.

High-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified » E 3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported high flux level. Taking into account the XMM measurement uncertainties for this region, the inconsistency with Hitomi is at a 99% significance for a broad dark matter line and at 99.7% for a narrow line from the gas. We do not find anomalously high fluxes of the nearby faint K line or the Ar satellite line that were proposed as explanations for the earlier 3.5 keV detections. We do find a hint of a broad excess near the energies of high-n transitions of S XVI (  E 3.44 keV rest-frame)-a possible signature of charge exchange in the molecular nebula and another proposed explanation for the unidentified line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. A confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.

High-resolution spectroscopy of the core of the Perseus Cluster of galaxies, using the Hitomi satellite above 2 keV and the XMM-Newton Reflection Grating Spectrometer at lower energies, provides reliable constraints on the abundances of O, Ne, Mg, Si, S, Ar, Ca, Cr, Mn, Fe, and Ni. Accounting for all known systematic uncertainties, the Ar/Fe, Ca/Fe, and Ni/Fe ratios are determined with a remarkable precision of less than 10%, while the constraints on Si/Fe, S/Fe, and Cr/Fe are at the 15% level, and Mn/Fe is measured with a 20% uncertainty. The average biases in determining the chemical composition using archival CCD spectra from XMM-Newton and Suzaku range typically from 15-40%. A simple model in which the enrichment pattern in the Perseus Cluster core and the proto-solar nebula are identical gives a surprisingly good description of the high-resolution X-ray spectroscopy results, with χ 2 = 10.7 for 10 d.o.f. However, this pattern is challenging to reproduce with linear combinations of existing supernova nucleosynthesis calculations, particularly given the precise measurements of intermediate α-elements enabled by Hitomi. We discuss in detail the degeneracies between various supernova progenitor models and explosion mechanisms, and the remaining uncertainties in these theoretical models. We suggest that including neutrino physics in the core-collapse supernova yield calculations may improve the agreement with the observed pattern of α-elements in the Perseus Cluster core. Our results provide a complementary benchmark for testing future nucleosynthesis calculations required to understand the origin of chemical elements.

Both heliophysics and planetary physics seek to understand the complex nature of the solar wind's interaction with solar system obstacles like Earth's magnetosphere, the ionospheres of Venus and Mars, and comets. Studies with this objective are frequently conducted with the help of single or multipoint in situ electromagnetic field and particle observations, guided by the predictions of both local and global numerical simulations, and placed in con- text by observations from far and extreme ultraviolet (FUV, EUV), hard X-ray, and energetic neutral atom imagers (ENA). Each proposed interaction mechanism (e.g., steady or transient magnetic reconnection, local or global magnetic reconnection, ion pick-up, or the KelvinHelmholtz instability) generates diagnostic plasma density structures. The significance of each mechanism to the overall interaction (as measured in terms of atmospheric/ionospheric loss at comets, Venus, and Mars or global magnetospheric/ionospheric convection at Earth) remains to be determined but can be evaluated on the basis of how often the density signatures that it generates are observed as a function of solar wind conditions. This paper reviews efforts to image the diagnostic plasma density structures in the soft (low energy, 0.1-2.0 keV) X-rays produced when high charge state solar wind ions exchange electrons with the exospheric neutrals surrounding solar system obstacles. The introduction notes that theory, local, and global simulations predict the characteristics of plasma boundaries such the bow shock and magnetopause (including location, density gradient, and motion) and regions such as the magnetosheath (including density and width) as a function of location, solar wind conditions, and the particular mechanism operating. In situ measurements confirm the existence of time-and spatial-dependent plasma density structures like the bow shock, magnetosheath, and magnetopause/ionopause at Venus, Mars, comets, and the Earth. However, in situ measurements rarely suffice to determine the global extent of these density structures or their global variation as a function of solar wind conditions, except in the form of empirical studies based on observations from many different times and solar wind conditions. Remote sensing observations provide global information about auroral ovals (FUV and hard X-ray), the terrestrial plasmasphere (EUV), and the terrestrial ring current (ENA). ENA instruments with low energy thresholds (∼ 1 keV) have recently been used to obtain important information concerning the magnetosheaths of Venus, Mars, and the Earth. Recent technological developments make these magnetosheaths valuable potential targets for high-cadence wide-field-of-view soft X-ray imagers.Section 2 describes proposed dayside interaction mechanisms, including reconnection, the Kelvin-Helmholtz instability, and other processes in greater detail with an emphasis on the plasma density structures that they generate. It focuses upon the questions that remain as yet unanswered, such as the significanc...

Chandra ACIS-I data of the molecular cloud and H ii region complex NGC 6334 were analyzed. The hard X-ray clumps detected with ASCA (Sekimoto and coworkers) were resolved into 792 point sources. After removing the point sources, an extended X-ray emission component was detected over a 5 ; 9 pc 2 region, with the 0.5-8 keV absorption-corrected luminosity of 2 ; 10 33 ergs s À1 . The contribution from faint point sources to this extended emission was estimated as at most $20%, suggesting that most of the emission is diffuse in nature. The X-ray spectrum of the diffuse emission was observed to vary from place to place. In tenuous molecular cloud regions with hydrogen column density of (0:5 1) ; 10 22 cm À2 , the spectrum can be represented by a thermal plasma model with temperatures of several keV. The spectrum in dense cloud cores exhibits harder continuum, together with higher absorption of more than $3 ; 10 22 cm À2 . In some of such highly obscured regions, the spectra show extremely hard continua equivalent to a photon index of $1, and favor a nonthermal interpretation. These results are discussed in the context of thermal and nonthermal emission, both powered by fast stellar winds from embedded young early-type stars through shock transitions.

No abstract

Jupiter's X‐ray auroral emission in the polar cap region results from particles which have undergone strong field‐aligned acceleration into the ionosphere. The origin of precipitating ions and electrons and the time variability in the X‐ray emission are essential to uncover the driving mechanism for the high‐energy acceleration. The magnetospheric location of the source field line where the X‐ray is generated is likely affected by the solar wind variability. However, these essential characteristics are still unknown because the long‐term monitoring of the X‐rays and contemporaneous solar wind variability has not been carried out. In April 2014, the first long‐term multiwavelength monitoring of Jupiter's X‐ray and EUV auroral emissions was made by the Chandra X‐ray Observatory, XMM‐Newton, and Hisaki satellite. We find that the X‐ray count rates are positively correlated with the solar wind velocity and insignificantly with the dynamic pressure. Based on the magnetic field mapping model, a half of the X‐ray auroral region was found to be open to the interplanetary space. The other half of the X‐ray auroral source region is magnetically connected with the prenoon to postdusk sector in the outermost region of the magnetosphere, where the Kelvin‐Helmholtz (KH) instability, magnetopause reconnection, and quasiperiodic particle injection potentially take place. We speculate that the high‐energy auroral acceleration is associated with the KH instability and/or magnetopause reconnection. This association is expected to also occur in many other space plasma environments such as Saturn and other magnetized rotators.