Browsing Articles by Subject "Accretion (Astrophysics)"

Browsing Articles by Subject "Accretion (Astrophysics)"

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  • Wurster, James Howard; Thacker, Robert John, 1970- (Oxford University Press, 2013-05)
    A recent approach to simulating localized feedback from active galactic nuclei (AGN) by Power et al. uses an accretion disc particle to represent both the black hole and its accretion disc. We have extrapolated and adapted ...

  • Siwak, Michal; Rucinski, Slavek M.; Matthews, Jaymie M.; Pojmanski, Grzegorz; Kuschnig, Rainer; Guenther, David B.; Moffat, Anthony F. J.; Sasselov, Dimitar; Weiss, Werner W. (Wiley-Blackwell, 2011-02)
    As a continuation of our previous studies in 2007 and 2008, new photometric observations of the T Tauri star TW Hya obtained by the MOST satellite and the All Sky Automated Survey (ASAS) project over 40 d in 2009 with ...

  • Wilkins, D. R.; Kara, E.; Fabian, A. C.; Gallo, Luigi C. (Oxford University Press, 2014-09-21)
    The X-ray spectra of the narrow-line Seyfert 1 galaxy, 1H 0707–495, obtained with XMM–Newton, from time periods of varying X-ray luminosity are analysed in the context of understanding the changes to the X-ray ...

  • Wilkins, D. R.; Gallo, Luigi C. (Oxford University Press, 2015-03-21)
    We consider the Comptonization of the photons that make up the relativistically blurred reflection that is commonly detected from the accretion discs of active galactic nuclei by the coronae of energetic particles believed ...

  • Wilkins, D. R.; Gallo, Luigi C. (Oxford University Press, 2015-05-01)
    Variations in the X-ray emission from the narrow-line Seyfert 1 galaxy, Markarian 335, are studied on both long and short time-scales through observations made between 2006 and 2013 with XMM–Newton, Suzaku and NuSTAR. ...

  • 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 ...

  • 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.; Fabian, A. C.; Kara, E.; Walton, D. J.; Wilkins, D. R.; Ross, R. R.; Lozanov, K.; Uttley, P.; Zoghbi, A.; Miniutti, G. (Oxford University Press, 2013-03-11)
    The narrow-line Seyfert 1 galaxy IRAS 13224−3809 has been observed with XMM–Newton for 500 ks. The source is rapidly variable on time-scales down to a few 100 s. The spectrum shows strong broad Fe − K and L emission ...

  • Cackett, E. M.; Zoghbi, A.; Reynolds, C.; Fabian, A. C.; Kara, E.; Uttley, P.; Wilkins, D. R. (Oxford University Press, 2014-01-13)
    The recent detection of X-ray reverberation lags, especially in the Fe Kα line region, around active galactic nuclei (AGN) has opened up the possibility of studying the time-resolved response (reflection) of hard ...

  • Miller, J. M.; Tomsick, J. A.; Bachetti, M.; Wilkins, D. R.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Fabian, A. C.; Grefenstette, B. W.; Hailey, C. J. (American Astronomical Society, 2015-01-20)
    We report on an observation of the Galactic black hole candidate GRS 1739−278 during its 2014 outburst, obtained with NuSTAR. The source was captured at the peak of a rising “low/hard” state, at a flux of ~0.3 Crab. A broad, ...

  • Gallo, Luigi C.; Fabian, A. C. (Oxford University Press, 2013-09)
    In some radio-quiet active galactic nuclei (AGN), high-energy absorption features in the X-ray spectra have been interpreted as ultrafast outflows (UFOs) – highly ionized material (e.g. Fe XXV and Fe XXVI) ejected at mildly ...

  • Siwak, Michal; Rucinski, Slavek M.; Matthews, Jaymie M.; Kuschnig, Rainer; Guenther, David B.; Moffat, Anthony F. J.; Rowe, Jason F.; Sasselov, Dimitar; Weiss, Werner W. (Oxford University Press, 2013-06)

    Photometric observations obtained by the MOST satellite were used to characterize optical small-scale variability of the young stars FU Ori and Z CMa. Wavelet analysis for FU Ori reveals the possible existence ...


  • Siwak, Michal; Ogloza, Waldemar; Rucinski, Slavek M.; Moffat, Anthony F. J.; Matthews, Jaymie M.; Cameron, Chris; Guenther, David B.; Kuschnig, Rainer; Rowe, Jason F.; Sasselov, Dimitar (Oxford University Press, 2016-03-11)
    Results of the time variability monitoring of the two classical T Tauri stars, RU Lup and IM Lup, are presented. Three photometric data sets were utilized: (1) simultaneous (same field) MOST satellite observations over ...

  • Siwak, Michal; Rucinski, Slavek M.; Matthews, Jaymie M.; Guenther, David B.; Kuschnig, Rainer; Moffat, Anthony F. J.; Rowe, Jason F.; Sasselov, Dimitar; Weiss, Werner W. (Oxford University Press, 2014-10-11)
    We present an analysis of the 2011 photometric observations of TW Hya by the MOST satellite; this is the fourth continuous series of this type. The large-scale light variations are dominated by a strong, quasi-periodic ...

  • 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 ...

  • Wilkins, D. R.; Cackett, E. M.; Fabian, A. C.; Reynolds, C. S. (Oxford University Press, 2016-05-01)
    Models of X-ray reverberation from extended coronae are developed from general relativistic ray tracing simulations. Reverberation lags between correlated variability in the directly observed continuum emission and that ...