Browsing by Author "Craig, W. W."

Now showing 1 - 11 of 11
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    Determining 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.
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    IC 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.
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    IC 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.
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    NuSTAR 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.
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    The 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.
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    THE NuSTAR EXTRAGALACTIC SURVEY: A FIRST SENSITIVE LOOK AT THE HIGH-ENERGY COSMIC X-RAY BACKGROUND POPULATION
    (2013) Alexander, D. M.; Stern, D.; Del Moro, A.; Lansbury, G. B.; Assef, R. J.; Aird, J.; Ajello, M.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Brandt, W. N.; Christensen, F. E.; Civano, F.; Comastri, A.; Craig, W. W.; Elvis, M.; Grefenstette, B. W.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Luo, B.; Madsen, K. K.; Mullaney, J. R.; Perri, M.; Puccetti, S.; Saez, C.; Treister, E.; Urry, C. M.; Zhang, W. W.; Bridge, C. R.; Eisenhardt, P. R. M.; Gonzalez, A. H.; Miller, S. H.; Tsai, C. W.
    We report on the first 10 identifications of sources serendipitously detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) to provide the first sensitive census of the cosmic X-ray background source population at greater than or similar to 10 keV. We find that these NuSTAR-detected sources are approximate to 100 times fainter than those previously detected at greater than or similar to 10 keV and have a broad range in redshift and luminosity (z = 0.020-2.923 and L10-40 keV approximate to 4 x 10(41)-5 x 10(45) erg s(-1)); the median redshift and luminosity are z approximate to 0.7 and L10-40 keV approximate to 3 x 10(44) erg s(-1), respectively. We characterize these sources on the basis of broad-band approximate to 0.5-32 keV spectroscopy, optical spectroscopy, and broad-band ultraviolet-to-mid-infrared spectral energy distribution analyses. We find that the dominant source population is quasars with L10-40 keV > 10(44) erg s(-1), of which approximate to 50% are obscured with N-H greater than or similar to 10(22) cm(-2). However, none of the 10 NuSTAR sources are Compton thick (N-H greater than or similar to 10(24) cm(-2)) and we place a 90% confidence upper limit on the fraction of Compton-thick quasars (L10-40 keV > 10(44) erg s(-1)) selected at greater than or similar to 10 keV of less than or similar to 33% over the redshift range z = 0.5-1.1. We jointly fitted the rest-frame approximate to 10-40 keV data for all of the non-beamed sources with L10-40 keV > 10(43) erg s(-1) to constrain the average strength of reflection; we find R < 1.4 for Gamma = 1.8, broadly consistent with that found for local active galactic nuclei (AGNs) observed at greater than or similar to 10 keV. We also constrain the host-galaxy masses and find a median stellar mass of approximate to 10(11) M-circle dot, a factor approximate to 5 times higher than the median stellar mass of nearby high-energy selected AGNs, which may be at least partially driven by the order of magnitude higher X-ray luminosities of the NuSTAR sources. Within the low source-statistic limitations of our study, our results suggest that the overall properties of the NuSTAR sources are broadly similar to those of nearby high-energy selected AGNs but scaled up in luminosity and mass.
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    THE BROADBAND SPECTRAL VARIABILITY OF MCG-6-30-15 OBSERVED BY NUSTAR AND XMM-NEWTON
    (2014) Marinucci, A.; Matt, G.; Miniutti, G.; Guainazzi, M.; Parker, M. L.; Brenneman, L.; Fabian, A. C.; Kara, E.; Arevalo, P.; Ballantyne, D. R.; Boggs, S. E.; Cappi, M.; Christensen, F. E.; Craig, W. W.; Elvis, M.; Hailey, C. J.; Harrison, F. A.; Reynolds, C. S.; Risaliti, G.; Stern, D. K.; Walton, D. J.; Zhang, W.
    MCG-6-30-15, at a distance of 37 Mpc (z = 0.008), is the archetypical Seyfert 1 galaxy showing very broad Fe K alpha emission. We present results from a joint NuSTAR and XMM-Newton observational campaign that, for the first time, allows a sensitive, time-resolved spectral analysis from 0.35 keV up to 80 keV. The strong variability of the source is best explained in terms of intrinsic X-ray flux variations and in the context of the light-bending model: the primary, variable emission is reprocessed by the accretion disk, which produces secondary, less variable, reflected emission. The broad Fe K alpha profile is, as usual for this source, well explained by relativistic effects occurring in the innermost regions of the accretion disk around a rapidly rotating black hole. We also discuss the alternative model in which the broadening of the Fe K alpha is due to the complex nature of the circumnuclear absorbing structure. Even if this model cannot be ruled out, it is disfavored on statistical grounds. We also detected an occultation event likely caused by broad-line region clouds crossing the line of sight.
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    The 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.
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    The 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.
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    The 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.
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    The 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