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Soft X-ray spectral variations of the narrow line Seyfert l galaxy Markarian 766

Page, MJ; Carrera, FJ; Mittaz, JPD; Mason, KO; (1999) Soft X-ray spectral variations of the narrow line Seyfert l galaxy Markarian 766. Monthly Notices of the Royal Astronomical Society , 305 (4) 775 - 794. 10.1046/j.1365-8711.1999.02489.x. Green open access

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Abstract

The X-ray variability of the narrow-line Seyfert 1 galaxy Markarian 766 is studied using nine ROSAT PSPC data sets. The spectrum is well described by a power law combined with a blackbody (kT ∼ 70 eV) soft excess. Examination of flux ratio changes and variability amplitude in three X-ray bands shows that the power-law component varies continuously on time-scales of ∼ 5000 s and is steeper when it is brighter. In contrast, variability of the soft excess is not detected. Spectral modelling of 31 spectra from different observations and at a range of count rates is also consistent with a picture in which the power law is steeper when it is brighter, and in which the soft-excess component does not vary. The power-law variability can be explained if the power law is produced by variable thermal or non-thermal Comptonization of soft photons. This behaviour is similar to that of Galactic black hole candidates in the low state. The X-ray and multiwavelength properties of Markarian 766 are shown to be very similar to those of other narrow-line Seyfert 1s. This may mean that the rapid X-ray variability seen in other narrow-line Seyfert 1s may also not originate in their strong soft-excess components.

Type: Article
Title: Soft X-ray spectral variations of the narrow line Seyfert l galaxy Markarian 766
Open access status: An open access version is available from UCL Discovery
DOI: 10.1046/j.1365-8711.1999.02489.x
Publisher version: http://dx.doi.org/10.1046/j.1365-8711.1999.02489.x
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: galaxies, galaxy, X-ray
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/31986
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