SAX J1808.4-3658 and the origin of X-Ray variability in X-Ray binaries and active galactic nuclei
SAX J1808.4-3658 and the origin of X-Ray variability in X-Ray binaries and active galactic nuclei
The aperiodic X-ray variability in neutron star and black hole X-ray binaries (XRBs) and active galactic nuclei (AGN) shows a characteristic linear relationship between rms amplitude and flux, implying a multiplying together or 'coupling' of variability on different time-scales. Such a coupling may result from avalanches of flares, due to magnetic reconnection in an X-ray-emitting corona. Alternatively this coupling may arise directly from the coupling of perturbations in the accretion flow, which propagate to the inner emitting regions and so modulate the X-ray emission. Here, we demonstrate explicitly that the component of aperiodic variability that carries the rms–flux relation in the accreting millisecond pulsar SAX J1808.4?3658 is also coupled to the 401-Hz pulsation in this source. This result implies that the rms–flux relation in SAX J1808.4?3658 is produced in the accretion flow on to the magnetic caps of the neutron star, and not in a corona. By extension we infer that propagating perturbations in the accretion flow, and not coronal flares, are the source of the rms–flux relations and hence the aperiodic variability in other XRBs and AGN.
X-rays: binaries – X-rays: individual: SAX J1808.4-3658 – X-rays: galax-ies – galaxies: active – accretion – instabilities
L61-L65
Uttley, Phillip
db770bd7-d97e-43f5-99d4-a585bccd352a
February 2004
Uttley, Phillip
db770bd7-d97e-43f5-99d4-a585bccd352a
Uttley, Phillip
(2004)
SAX J1808.4-3658 and the origin of X-Ray variability in X-Ray binaries and active galactic nuclei.
Monthly Notices of the Royal Astronomical Society, 347 (4), .
(doi:10.1111/j.1365-2966.2004.07434.x).
Abstract
The aperiodic X-ray variability in neutron star and black hole X-ray binaries (XRBs) and active galactic nuclei (AGN) shows a characteristic linear relationship between rms amplitude and flux, implying a multiplying together or 'coupling' of variability on different time-scales. Such a coupling may result from avalanches of flares, due to magnetic reconnection in an X-ray-emitting corona. Alternatively this coupling may arise directly from the coupling of perturbations in the accretion flow, which propagate to the inner emitting regions and so modulate the X-ray emission. Here, we demonstrate explicitly that the component of aperiodic variability that carries the rms–flux relation in the accreting millisecond pulsar SAX J1808.4?3658 is also coupled to the 401-Hz pulsation in this source. This result implies that the rms–flux relation in SAX J1808.4?3658 is produced in the accretion flow on to the magnetic caps of the neutron star, and not in a corona. By extension we infer that propagating perturbations in the accretion flow, and not coronal flares, are the source of the rms–flux relations and hence the aperiodic variability in other XRBs and AGN.
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Published date: February 2004
Keywords:
X-rays: binaries – X-rays: individual: SAX J1808.4-3658 – X-rays: galax-ies – galaxies: active – accretion – instabilities
Identifiers
Local EPrints ID: 38394
URI: http://eprints.soton.ac.uk/id/eprint/38394
ISSN: 1365-2966
PURE UUID: 23730729-4b51-481e-baa4-341269da838d
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Date deposited: 09 Jun 2006
Last modified: 15 Mar 2024 08:07
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Author:
Phillip Uttley
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