Abstract. SPI is a high spectral resolution gamma-ray telescope on board the ESA mission INTEGRAL (International Gamma Ray Astrophysics Laboratory). It consists of an array of 19 closely packed germanium detectors surrounded by an active anticoincidence shield of BGO. The imaging capabilities of the instrument are obtained with a tungsten coded aperture mask located 1.7 m from the Ge array. The fully coded field-of-view is 16• , the partially coded field of view amounts to 31• , and the angular resolution is 2.5• . The energy range extends from 20 keV to 8 MeV with a typical energy resolution of 2.5 keV at 1.3 MeV. Here we present the general concept of the instrument followed by a brief description of each of the main subsystems. INTEGRAL was successfully launched in October 2002 and SPI is functioning extremely well.

The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband X-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 10 46 ergs per second is enough to provide the feedback required by models of black hole and host galaxy co-evolution.Disk winds are theoretically expected as a natural consequence of highly efficient accretion onto supermassive black holes (1), as the energy radiated in this process might easily exceed the local binding energy of the gas. In the past few years, black hole winds with column densities of ~10 23 cm -2 and velocities of ~0.1 times the speed of light (c) have been revealed in a growing number of nearby active galactic nuclei (AGN) through blueshifted X-ray absorption lines (2,3). Outflows of this kind are commonly believed to affect the dynamical and physical properties of the gas in the host galaxy, and, hence, its star formation history (4). However, a complete observational characterization of how this feedback works is still missing. On its own, the detection of narrow, blueshifted features does not convey any information about the opening angle or the ejection site of the wind. This knowledge is critical for measuring the total power carried by the outflow, whose actual influence on galactic scales remains unclear (5).The nearby (z = 0.184) radio-quiet quasar PDS 456 is an established Rosetta stone for studying disk winds (6-8). With a bolometric luminosity L bol ~ 10 47 erg/s, and a mass of the central black hole on the order of 10 9 solar masses (M sun ) (9), it is an exceptionally luminous AGN in the local universe and might be regarded as a counterpart of the accreting supermassive black holes during the peak of quasar activity at high redshift. Since the earliest X-ray observations, PDS 456 has regularly exhibited a deep absorption trough at rest-frame energies above 7 keV (6), which was occasionally resolved with high statistical significance into a pair of absorption lines at ~9.09 and 9.64 keV (7). Because no strong atomic transitions from cosmically abundant elements correspond to these energies, such lines are most likely associated with resonant K-shell absorption from Fe XXV Heα (6.7 keV) and Fe XXVI Lyα (6.97 keV) in a wind with an outflow velocity of ~0.3c.The X-ray Multi-Mirror Mission (XMM)-Newton and Nuclear Spectroscopic Telescope Array (NuSTAR) satellites simultaneously observed PDS 456 on four occasions in 2013, between 27 August and 21 September. A fifth observation was performed several months later, on 26 February 2014 (Table S...

The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, with most detections being either of low significance or controversial. Because all prior telescopes sensitive at E > 10 keV do not focus light and have degree-scale fields of view, their backgrounds are both high and difficult to characterize. The associated uncertainties result in lower sensitivity to IC emission and a greater chance of false detection. In this work, we present 266 ks NuSTAR observations of the Bullet cluster, which is detected in the energy range 3-30 keV. NuSTAR's unprecedented hard X-ray focusing capability largely eliminates confusion between diffuse IC and point sources; however, at the highest energies, the background still dominates and must be well understood. To this end, we have developed a complete background model constructed of physically inspired components constrained by extragalactic survey field observations, the specific parameters of which are derived locally from data in non-source regions of target observations. Applying the background model to the Bullet cluster data, we find that the spectrum is well-but not perfectly-described as an isothermal plasma with kT = 14.2 ± 0.2 keV. To slightly improve the fit, a second temperature component is added, which appears to account for lower temperature emission from the cool core, pushing the primary component to kT ∼ 15.3 keV. We see no convincing need to invoke an IC component to describe the spectrum of the Bullet cluster, and instead argue that it is dominated at all energies by emission from purely thermal gas. The conservatively derived 90% upper limit on the IC flux of 1.1 × 10 −12 erg s −1 cm −2 (50-100 keV), implying a lower limit on B 0.2 μG, is barely consistent with detected fluxes previously reported. In addition to discussing the possible origin of this discrepancy, we remark on the potential implications of this analysis for the prospects for detecting IC in galaxy clusters in the future.

We present the calibration of the Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray satellite. We used the Crab as the primary effective area calibrator and constructed a piece-wise linear spline function to modify the vignetting response. The achieved residuals for all off-axis angles and energies, compared to the assumed spectrum, are typically better than ±2% up to 40 keV and 5-10 % above due to limited counting statistics. An empirical adjustment to the theoretical 2D point spread function (PSF) was found using several strong point sources, and no increase of the PSF half power diameter (HPD) has been observed since the beginning of the mission. We report on the detector gain calibration, good to 60 eV for all grades, and discuss the timing capabilities of the observatory, which has an absolute timing of ± 3 ms. Finally we present cross-calibration results from two campaigns between all the major concurrent X-ray observatories (Chandra, Swift, Suzaku and XMM-Newton), conducted in 2012 and 2013 on the sources 3C 273 and PKS 2155-304, and show that the differences in measured flux is within ∼10% for all instruments with respect to NuSTAR. Subject headings: space vehicles: instruments -X-rays: individual (3C 273) -X-rays: individual (PKS 2155-304)

We report on observations of NGC 1068 with NuSTAR, which provide the best constraints to date on its > 10 keV spectral shape. The NuSTAR data are consistent with past instruments, with no strong continuum or line variability over the past two decades, consistent with its classification as a Compton-thick AGN. The combined NuSTAR, Chandra, XMM-Newton, and Swift BAT spectral dataset offers new insights into the complex secondary emission seen instead of the completely obscured transmitted nuclear continuum. The critical combination of the high signal-to-noise NuSTAR data and the decomposition of the nuclear and extranuclear emission with Chandra allow us to break several model degeneracies and greatly aid physical interpretation. When modeled as a monolithic (i.e., a single N H ) reflector, none of the common Compton-reflection models are able to match the neutral fluorescence lines and broad spectral shape of the Compton reflection without requiring unrealistic physical parameters (e.g., large Fe overabundances, inconsistent viewing angles, poor fits to the spatially resolved spectra). A multi-component reflector with three distinct column densities (e.g., with best-fit values of N H = 1.5 × 10 23 , 5 × 10 24 , and 10 25 cm −2 ) provides a more reasonable fit to the spectral lines and Compton hump, with near-solar Fe abundances. In this model, the higher N H component provides the bulk of the flux to the Compton hump while the lower N H component produces much of the line emission, effectively decoupling two key features of Compton reflection. We also find that ≈30% of the neutral Fe Kα line flux arises from >2 ′′ (≈140 pc) and is clearly extended, implying that a significant fraction of the <10 keV reflected component arises from regions well outside of a parsec-scale torus. These results likely have ramifications for the interpretation of Compton-thick spectra from observations with poorer signal-to-noise and/or more distant objects.