Browsing by Author "Christensen, F. E."
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- ItemDetermining the covering factor of compton-thick active galactic nuclei with NuSTAR(2015) Brightman, M.; Balokovic, M.; Stern, D.; Arevalo, P.; Ballantyne, D. R.; Bauer, Franz Erik; Bogg, S. E.; Craig, W. W.; Christensen, F. E.; Comastri, A.; Gandhi, P.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Koss, M.; Lamassa, S.; Fuerst, F.; Puccetti, S.; Rivers, E.; Vasudevan, R.; Walton, D. J.; Zhang, W. W.
- ItemIC 3639—A NEW BONA FIDE COMPTON-THICK AGN UNVEILED BY NuSTAR(2016) Boorman, Peter G.; Gandhi, P.; Alexander, D. M.; Annuar, A.; Ballantyne, D. R.; Bauer, Franz Erik; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Farrah, D.; Hailey, C. J.; Harrison, F. A.; Hönig, S. F.; Koss, M.; LaMassa, S. M.; Masini, A. C.; Ricci, G.; Risaliti, D.; Stern, W.; Zhang, W.
- ItemIC 751: A New Changing Look AGN Discovered by NuSTAR.(2016) Ricci, Claudio; Bauer, Franz Erik; Treister, Ezequiel; Arévalo, Patricia.; Boggs, Steven E.; Brandt, W. N.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Hailey, C. J.; Harrison, F. A.
- ItemNuSTAR observations of water megamaser AGN(2016) Masini, A.; Comastri, A.; Baloković, M.; Zaw, I.; Puccetti, S.; Ballantyne, D. R.; Bauer, Franz Erik; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Hailey, C. J.; Harrison, F. A.; Koss, M. J.; Madejski, G.; Ricci, Claudio; Rivers, E.; Stern, D.
- ItemThe 2-79 keV X-Ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton, and Chandra: A Fully Compton-thick Active Galactic Nucleus(2014) Arévalo, Patricia.; Treister, Ezequiel; Bauer, Franz Erik; Puccetti, S.; Walton, D. J.; Koss, M.; Boggs, Steve E.; Brandt, W N.; Brightman, M.; Christensen, F. E.; Comastri, A.; Craig, W. W.
- ItemThe Multi-Layer Variable Absorbers in NGC 1365 Revealed by XMM-Newton and NuSTAR(2015) Rivers, E.; Risaliti, G.; Walton, D. J.; Harrison, F.; Arévalo, P.; Bauer, Franz Erik; Boggs, S. E.; Brenneman, L. W.; Brightman, M.; Christensen, F. E.
- ItemThe NuSTAR view of the non-thermal emission from PSR J0437-4715(OXFORD UNIV PRESS, 2016) Guillot, S.; Kaspi, V. M.; Archibald, R. F.; Bachetti, M.; Flynn, C.; Jankowski, F.; Bailes, M.; Boggs, S.; Christensen, F. E.; Craig, W. W.; Hailey, C. A.; Harrison, F. A.; Stern, D.; Zhang, W. W.We present a hard X-ray Nuclear Spectroscopic Telescope Array (NuSTAR) observation of PSR J0437-4715, the nearest millisecond pulsar. The known pulsations at the apparent pulse period similar to 5.76 ms are observed with a significance of 3.7 sigma, at energies up to 20 keV above which the NuSTAR background dominates. We measure a photon index Gamma = 1.50 +/- 0.25 (90 per cent confidence) for the power-law fit to the non-thermal emission. It had been shown that spectral models with two or three thermal components fit the XMM-Newton spectrum of PSR J0437-4715, depending on the slope of the power-law component, and the amount of absorption of soft X-rays. The new constraint on the high-energy emission provided by NuSTAR removes ambiguities regarding the thermal components of the emission below 3 keV. We performed a simultaneous spectral analysis of the XMM-Newton and NuSTAR data to confirm that three thermal components and a power law are required to fit the 0.3-20 keV emission of PSR J0437-4715. Adding a ROSAT-PSPC spectrum further confirmed this result and allowed us to better constrain the temperatures of the three thermal components. A phase-resolved analysis of the NuSTAR data revealed no significant change in the photon index of the high-energy emission. This NuSTAR observation provides further impetus for future observations with the NICER mission (Neutron Star Interior Composition Explorer) whose sensitivity will provide much stricter constraints on the equation of state of nuclear matter by combining model fits to the pulsar's phase-folded light curve with the pulsar's well-defined mass and distance from radio timing observations.
- ItemThe Seyfert 2 galaxy NGC 2110 : hard X-ray emission observed by NuSTAR and variability of the iron Kα line(2015) Marinucci, A.; Matt, G.; Bianchi, S.; Lu, T. N.; Arévalo, P.; Balokovic, M.; Ballantyne, D.; Bauer, Franz Erik; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Hailey, C. J.; Harrison, F.; Puccetti, S.; Rivers, E.; Walton, D. J.; Stern, D.; Zhang, W.
- ItemThe soft-X-ray emission of Ark 120. XMM-Newton, NuSTAR, and the importance of taking the broad view(OXFORD UNIV PRESS, 2014) Matt, G.; Marinucci, A.; Guainazzi, M.; Brenneman, L. W.; Elvis, M.; Lohfink, A.; Arevalo, P.; Boggs, S. E.; Cappi, M.; Christensen, F. E.; Craig, W. W.; Fabian, A. C.; Fuerst, F.; Hailey, C. J.; Harrison, F. A.; Parker, M.; Reynolds, C. S.; Stern, D.; Walton, D. J.; Zhang, W. W.We present simultaneous XMM-Newton and NuSTAR observations of the 'bare' Seyfert 1 galaxy, Ark 120, a system in which ionized absorption is absent. The NuSTAR hard-X-ray spectral coverage allows us to constrain different models for the excess soft-X-ray emission. Among phenomenological models, a cutoff power law best explains the soft-X-ray emission. This model likely corresponds to Comptonization of the accretion disc seed UV photons by a population of warm electrons: using Comptonization models, a temperature of similar to 0.3 keV and an optical depth of similar to 13 are found. If the UV-to-X-ray optxagnf model is applied, the UV fluxes from the XMM-Newton Optical Monitor suggest an intermediate black hole spin. Contrary to several other sources observed by NuSTAR, no high-energy cutoff is detected with a lower limit of 190 keV.
- ItemThe X-Ray Reflection Spectrum of the Radio-loud Quasar 4C 74.26(2017) Lohfink, Anne M.; Fabian, Andrew C.; Ballantyne, David R.; Boggs, S. E.; Boorman, Peter; Christensen, F. E.; Craig, W. W.; Farrah, Duncan; García, Javier; Ricci, Claudio