The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 2012 June 13, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates in the band from 3 to 79 keV, extending the sensitivity of focusing far beyond the ∼10 keV high-energy cutoff achieved by all previous X-ray satellites. The inherently low background associated with concentrating the X-ray light enables NuSTAR to probe the hard X-ray sky with a more than 100-fold improvement in sensitivity over the collimated or coded mask instruments that have operated in this bandpass. Using its unprecedented combination of sensitivity and spatial and spectral resolution, NuSTAR will pursue five primary scientific objectives: (1) probe obscured active galactic nucleus (AGN) activity out to the

Some supernovae (SNe) may be powered by the interaction of the SN ejecta with a large amount of circumstellar matter (CSM). However, quantitative estimates of the CSM mass around such SNe are missing when the CSM material is optically thick. Specifically, current estimators are sensitive to uncertainties regarding the CSM density profile and the ejecta velocity. Here we outline a method to measure the mass of the optically thick CSM around such SNe. We present new visible-light and X-ray observations of SN 2010jl (PTF 10aaxf), including the first detection of a SN in the hard X-ray band using NuSTAR. The total radiated luminosity of SN 2010jl is extreme, at least 9 × 10 50 erg. By modeling the visible-light data, we robustly show that the mass of the circumstellar material within ∼ 10 16 cm of the progenitor of SN 2010jl was in excess of 10 M ⊙ . This mass was likely ejected tens of years prior to the SN explosion. Our modeling suggests that the shock velocity during shock breakout was ∼ 6000 km s −1 , decelerating to ∼ 2600 km s −1 about two years after maximum light. Furthermore, our late-time NuSTAR and XMM spectra of the SN presumably provide the first direct measurement of SN shock velocity two years after the SN maximum light -measured to be in the range of 2000 km s −1 to 4500 km s −1 if the ions and electrons are in equilibrium, and > ∼ 2000 km s −1 if they are not in equilibrium. This measurement is in agreement with the shock velocity predicted by our modeling of the visible-light data. Our observations also show that the average radial density distribution of the CSM roughly follows an r −2 law. A possible explanation for the > ∼ 10 M ⊙ of CSM and the wind-like profile is that they are the result of multiple pulsational pair instability events prior to the SN explosion, separated from each other by years.

We report the discovery of 3.76-s pulsations from a new burst source near Sgr A* observed by the NuSTAR Observatory. The strong signal from SGR J1745−29 presents a complex pulse profile modulated with pulsed fraction 27 ± 3% in the 3 − 10 keV band. Two observations spaced 9 days apart yield a spin-down rate ofṖ = (6.5 ± 1.4) × 10 −12 . This implies a magnetic field B = 1.6 × 10 14 G, spin-down powerĖ= 5 × 10 33 erg s −1 , and characteristic age P/2Ṗ = 9 × 10 3 yr, for the rotating dipole model. However, the currentṖ may be erratic, especially during outburst. The flux and modulation remained steady during the observations and the 3 − 79 keV spectrum is well fitted by a combined blackbody plus power-law model with temperature k T BB = 0.96 ± 0.02 keV and photon index Γ = 1.5 ± 0.4. The neutral hydrogen column density (N H ∼ 1.4 × 10 23 cm −2 ) measured by NuSTAR and Swift suggests that SGR J1745−29 is located at or near the Galactic Center. The lack of an X-ray counterpart in the published Chandra survey catalog sets a quiescent 2 − 8 keV luminosity limit of L x < ∼ 10 32 erg s −1 . The bursting, timing, and spectral properties indicate a transient magnetar undergoing an outburst with 2 − 79 keV luminosity up to 3.5 × 10 35 erg s −1 for a distance of 8 kpc. SGR J1745−29 joins a growing subclass of transient magnetars, indicating that many magnetars in quiescence remain undetected in the X-ray band or have been detected as high-B radio pulsars. The peculiar location of SGR J1745−29 has important implications for the formation and dynamics of neutron stars in the Galactic Center region.

Sagittarius A ⋆ harbors the supermassive black hole that lies at the dynamical center of our Galaxy. Sagittarius A ⋆ spends most of its time in a low luminosity emission state but flares frequently in the infrared and X-ray, increasing up to a few hundred fold in brightness for up to a few hours at a time. The physical processes giving rise to the X-ray flares are uncertain. Here we report the detection with the NuSTAR observatory in Summer and Fall 2012 of four low to medium amplitude X-ray flares to energies up to 79 keV. For the first time, we clearly see that the power-law spectrum of Sagittarius A ⋆ X-ray flares extends to high energy, with no evidence for a cut off. Although the photon index of the absorbed power-law fits are in agreement with past observations, we find a difference between the photon index of two of the flares (significant at the 95% confidence level). The spectra of the two brightest flares (∼55 times quiescence in the 2-10 keV band) are compared to simple physical models in an attempt to identify the main X-ray emission mechanism, but the data do not allow us to significantly discriminate between them. However, we confirm the previous finding that the parameters obtained with synchrotron models are, for the X-ray emission, physically more reasonable than those obtained with inverse-Compton models. One flare exhibits large and rapid (< 100 s) variability, which, considering the total energy radiated, constrains the location of the flaring region to be within ∼10 Schwarzschild radii of the black hole.

We present a statistical analysis of the X-ray flux distribution of Sgr A * from the Chandra X-ray Observatory's 3 Ms Sgr A * X-ray Visionary Project (XVP) in 2012. Our analysis indicates that the observed X-ray flux distribution can be decomposed into a steady quiescent component, represented by a Poisson process with rate Q = (5.24±0.08)×10 −3 cts s −1 , and a variable component, represented by a power law process (dN/dF ∝ F −ξ , ξ = 1.92 +0.03 −0.02 ). This slope matches our recently-reported distribution of flare luminosities. The variability may also be described by a log-normal process with a median unabsorbed 2-8 keV flux of 1.8 +0.9 −0.6 × 10 −14 erg s −1 cm −2 and a shape parameter σ = 2.4 ± 0.2, but the power law provides a superior description of the data. In this decomposition of the flux distribution, all of the intrinsic X-ray variability of Sgr A * (spanning at least three orders of magnitude in flux) can be attributed to flaring activity, likely in the inner accretion flow. We confirm that at the faint end, the variable component contributes ∼ 10% of the apparent quiescent flux, as previously indicated by our statistical analysis of X-ray flares in these Chandra observations. Our flux distribution provides a new and important observational constraint on theoretical models of Sgr A * , and we use simple radiation models to explore the extent to which a statistical comparison of the X-ray and infrared can provide insights into the physics of the X-ray emission mechanism.