Browsing Articles by Subject "Active galaxies"

Browsing Articles by Subject "Active galaxies"

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  • Gallo, Luigi C.; Bonson, K.; Fabian, A. C.; Grupe, D.; Komossa, S.; Longinotti, A. L.; Miniutti, G.; Walton, D. J.; Zoghbi, A.; Mathur, S. (Oxford University Press, 2013-01)
    As part of a long-term monitoring campaign of Mrk 335, deep XMM–Newton observations catch the narrow-line Seyfert 1 galaxy (NLS1) in a complex, intermediate flux interval as the active galaxy is transiting from low to high ...

  • Wilkins, D. R.; Gallo, Luigi C.; Grupe, D.; Bonson, K.; Komossa, S.; Fabian, A. C. (Oxford University Press, 2015-12-21)
    Monitoring of the narrowline Seyfert 1 galaxy Markarian 335 (Mrk 335) with the Swift satellite discovered an X-ray flare beginning 2014 August 29. At the peak, the 0.5–5 keV count rate had increased from that in the low-flux ...

  • Clarke, David A.; Harris, D. E.; Carilli, C. L. (Royal Astronomical Society and Oxford University Press, 1997)
    The ROSAT data from the cluster gas of Cygnus A are re-examined in light of a three-dimensional hydrodynamic simulation of a supersonic jet propagating in an isothermal King atmosphere designed to follow the observed density ...

  • Vasudevan, Ranjan V.; Mushotzky, Richard F.; Reynolds, Christopher S.; Fabian, Andrew C.; Lohfink, Anne M.; Zoghbi, Abderahmen; Gallo, Luigi C.; Walton, Dominic (IOP Publishing Limited, 2014-04-10)
    The X-ray spectra of many active galactic nuclei exhibit a “soft excess” below 1 keV, whose physical origin remains unclear. Diverse models have been suggested to account for it, including ionized reflection ...

  • Gallo, Luigi C.; Fabian, A. C. (Oxford University Press on behalf of the Royal Astronomical Society, 2011-11)
    Narrow absorption lines seen in the 2–10 keV spectra of active galaxies and Galactic black holes are normally attributed to iron in high-velocity outflows or inflows. We consider the possibility that such features could ...

  • Gallo, Luigi C.; Miniutti, G.; Brandt, W. N.; Schneider, D. P.; Fabian, A. C.; Boller, Th. (Royal Astronomical SocietyOxford University Press, 2012)
    PHL 1092 is a z ∼ 0.4 high-luminosity counterpart of the class of Narrow-Line Seyfert 1 galaxies. In 2008, PHL 1092 was found to be in a remarkably low X-ray flux state during an XMM–Newton observation. Its 2 keV flux ...

  • Bonson, K.; Gallo, Luigi C.; Vasudevan, R. (Oxford University Press, 2015-06-11)
    A multi-epoch, multi-instrument analysis of the Seyfert 1 galaxy HE 0436–4717 is conducted using optical to X-ray data from XMM–Newton and Swift (including the Burst Alert Telescope). Fitting of the UV-to-X-ray spectral ...

  • Gallo, Luigi C.; Miniutti, G.; Miller, J. M.; Brenneman, L. W.; Fabian, A. C.; Guainazzi, M.; Reynolds, C. S. (Oxford University Press, 2011-02)
    Multi-epoch X-ray spectroscopy (0.3–25 keV) of the Seyfert 1.2 galaxy Mrk 79 (UGC3973) spanning nearly 8 yr and a factor of 3 in broad-band flux are analysed. The data are obtained at seven epochs with either XMM–Newton ...

  • Gallo, Luigi C.; Miniutti, G.; Fabian, A. C.; Brandt, W. N.; Boller, Th. (Royal Astronomical SocietyOxford University Press, 2009)
    We report a dramatic variability event in the X-ray history of the narrow-line quasar PHL 1092 (z = 0.396). Our latest 2008 XMM-Newton observation reveals a flux drop of ∼200 with respect to the previous observation performed ...

  • Gallo, Luigi C.; Gruberbauer, Michael; Grupe, Dirk; Komossa, S.; Longinotti, Anna Lia; Fabian, Andrew C.; Pradhan, Anil K.; Xu, Dawei (American Astronomical Society, 2012-04)
    The narrow-line Seyfert 1 galaxy (NLS1) Mkn 335 is remarkable because it has repeatedly shown deep, long X-ray low states that show pronounced spectral structure. It has become one of the prototype active galactic nuclei ...

  • Gallo, Luigi C.; Longinotti, A. L.; Krongold, Y.; Kriss, G. A.; Ely, J.; Grupe, D.; Komossa, S.; Mathur, S.; Pradhan, A. (American Astronomical SocietyIOP Publishing, 2013-04-01)
    We present the discovery of an outflowing ionized wind in the Seyfert 1 galaxy Mrk 335. Despite having been extensively observed by most of the largest X-ray observatories in the last decade, this bright source was not ...

  • Robertson, D. R. S.; Gallo, Luigi C.; Zoghbi, A.; Fabian, A. C. (Oxford University Press, 2015-09-09)
    We examine simultaneous X-ray and UV light curves from multi-epoch 8 d XMM–Newton observations of the narrow line Seyfert 1 galaxy 1H 0707–495. The simultaneous observations reveal that both X-ray and UV emission are ...

  • Gallo, Luigi C.; Bachev, R.; Grupe, D.; Boeva, S.; Ovcharov, E.; Valcheva, A.; Semkov, E.; Georgiev, Ts. (Oxford University Press, 2009-10)
    We present the results from a monitoring campaign of the Narrow-Line Seyfert 1 galaxy PG 1211+143. The object was monitored with ground-based facilities (UBVRI photometry; from 2007 February to July) and with Swift [X-ray ...

  • Gallo, Luigi C.; Iwasawa, K.; Tanaka, Y. (EDP Sciences, 2010-05)
    We present a Suzaku observation of the dwarf Seyfert galaxy NGC 4395 with an estimated black hole mass of ~105M[subscript circled dot]. Rapid and strong X-ray variability with an rms amplitude of ~60 per cent is observed ...

  • Gallo, Luigi C.; Wilkins, D. R.; Bonson, K.; Chiang, C.-Y.; Grupe, D.; Parker, M. L.; Zoghbi, A.; Fabian, A. C.; Komossa, S.; Longinotti, A. L. (Oxford University Press, 2015-01)
    We report on the deepest X-ray observation of the narrow-line Seyfert 1 galaxy Mrk 335 in the low-flux state obtained with Suzaku. The data are compared to a 2006 high-flux Suzaku observation when the source was ∼10 times ...

  • Gallo, Luigi C.; Grupe, Dirk; Komossa, Stefanie; Fabian, Andrew C.; Larsson, Josefin; Pradhan, Anil K.; Xu, Dawei; Miniutti, Giovanni (American Astronomical Society, 2008-07)
    We report the discovery of strong soft X-ray emission lines and a hard continuum above 2 keV in the narrow-line Seyfert 1 galaxy Mrk 335 during an extremely low X-ray flux state. Mrk 335 was observed for 22 ks by XMM-Newton ...