Bibcode
González-Martín, O.; Vaughan, S.
Bibliographical reference
Astronomy and Astrophysics, Volume 544, id.A80
Advertised on:
8
2012
Journal
Citations
184
Refereed citations
174
Description
Context. Active galactic nuclei (AGN), powered by accretion onto
supermassive black holes (SMBHs), are thought to be scaled up versions
of Galactic black hole X-ray binaries (BH-XRBs). In the past few years
evidence of such correspondence include similarities in the broadband
shape of the X-ray variability power spectra, with characteristic bend
times-scales scaling with mass. Aims: The aim of this project is
to characterize the X-ray temporal properties of a sample of AGN to
study the connection among different classes of AGN and their connection
with BH-XRBs. Methods: We have performed a uniform analysis of
the power spectrum densities (PSDs) of 104 nearby (z < 0.4) AGN using
209 XMM-Newton/pn observations. These PSDs span ≃ 3 decades in
temporal frequencies, ranging from minutes to days. The PSDs have been
estimated in three energy bands: 0.2-10 (total), 0.2-2 (soft), and 2-10
keV (hard). The sample comprises 61 Type-1 AGN, 21 Type-2 AGN, 15 NLSy1,
and 7 BLLACS. We have fitted each PSD to two models: (1) a single
power-law model and (2) a bending power-law model. Results: Among
the entire sample, 72% show significant variability in at least one of
the three bands tested. A high percentage of low-luminosity AGN do not
show any significant variability (86% of LINERs). The PSD of the
majority of the variable AGN was well described by a simple power-law
with a mean index of α = 2.01 ± 0.01. In 15 sources we
found that the bending power law model was preferred with a mean slope
of α = 3.08 ± 0.04 and a mean bend frequency of ⟨
νb ⟩ ≃ 2 × 10-4 Hz. Only KUG
1031+398 (RE J1034+396) shows evidence for quasi-periodic oscillations.
The "fundamental plane" relating variability timescale, black hole mass,
and luminosity is demonstrated using the new X-ray timing results
presented here together with a compilation of the previously detected
timescales from the literature. Conclusions: Both quantitative
(i.e. scaling with BH mass) and qualitative (overall PSD shapes) found
in this sample of AGN are in agreement with the expectations for the
SMBHs and BH-XRBs being the same phenomenon scaled-up with the size of
the BH. The steep PSD slopes above the high frequency bend bear a closer
resemblance to those of the "soft/thermal dominated" BH-XRB states than
other states.
Tables 1-4 and Appendices A and B are available in electronic form at http://www.aanda.org
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