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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

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Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very bright and highly variable X-ray emission that are believed to be powered by ultra-strong magnetic fields of > 10 14 G, according to the 'magnetar' model. 1 The radio pulsations that have been observed from more than 1,700 neutron stars with weaker magnetic fields have never been detected from any of the dozen known magnetars. The X-ray pulsar XTE J1810-197 was revealed (in 2003) as the first AXP with transient emission when its luminosity increased 100-fold from the quiescent level 2 ; a coincident radio source of unknown origin was detected one year later. 3 Here we show that XTE J1810-197 emits bright, narrow, highly linearly polarized radio pulses, observed at every rotation, thereby establishing that magnetars can be radio pulsars. There is no evidence of radio emission before the 2003 X-ray outburst (unlike ordinary pulsars, which emit radio pulses all the time), and the flux varies from day to day. The flux at all radio frequencies is approximately equal -and at > 20 GHz XTE J1810-197 is currently the brightest neutron star known. These observations link magnetars to ordinary radio pulsars, rule out alternative accretion models for AXPs, and provide a new window into the coronae of magnetars. Pulsations with period P = 5.54 s were easily detected, with period-averaged flux density S 1.4 = 6 mJy and a narrow average profile with full-width at half-maximum of 0.15 s (Fig. 1). We detected individual pulses from virtually every rotation of the neutron star (see Fig. 2). These are composed of < ∼ 10-ms-wide sub-pulses with peak flux densities up to > ∼ 10 Jy and follow a differential flux distribution approximated by d log N = −d log S, with no giant pulses like those observed from the Crab pulsar. 6 A timing model accounting for every turn of the neutron star during the period 17 March-7 May yields barycentric P = 5.54024870 s± 20 ns on MJD 53855.0 anḋ P = (1.016 ± 0.001) × 10 −11 , with root-mean-square residual σ = 5 ms. We use this to set constraints on any putative companion to the AXP by requiring the light-traveltime across the projected orbital semi-major axis to be less than σ. From Kepler's third law, with assumed neutron star mass 1.4 M ⊙ , the upper limits on the minimum companion mass lie in the range ∼ 0.003-0.03 M ⊙ for orbital periods in the range 2 h-5 min, effectively ruling out the existence of any Roche lobe-filling star orbiting this AXP. The delay in pulse arrival times measured between 2.9 and 0.7 GHz implies an integrated column density of free electrons between the Earth and XTE J1810-197 of 178 ± 5 cm −3 pc. Together with a model for the Galactic distribution of free electrons, 7 the distance to XTE J1810-197 is D ≈ 3.3 kpc (here we use ≈ to indicate a quantity known to within about a factor of two or better), consistent with X-ray-and optically-derived estimates of 2.5-5 kpc (refs 8-10

The Palomar Transient Factory (PTF) is a wide-field experiment designed to investigate the optical transient and variable sky on time scales from minutes to years. PTF uses the CFH12k mosaic camera, with a field of view of 7.9 deg^2 and a plate scale of 1 asec/pixel, mounted on the the Palomar Observatory 48-inch Samuel Oschin Telescope. The PTF operation strategy is devised to probe the existing gaps in the transient phase space and to search for theoretically predicted, but not yet detected, phenomena, such as fallback supernovae, macronovae, .Ia supernovae and the orphan afterglows of gamma-ray bursts. PTF will also discover many new members of known source classes, from cataclysmic variables in their various avatars to supernovae and active galactic nuclei, and will provide important insights into understanding galactic dynamics (through RR Lyrae stars) and the Solar system (asteroids and near-Earth objects). The lessons that can be learned from PTF will be essential for the preparation of future large synoptic sky surveys like the Large Synoptic Survey Telescope. In this paper we present the scientific motivation for PTF and describe in detail the goals and expectations for this experiment.Comment: 15 pages, 6 figures, submitted to PAS