Change search
ReferencesLink to record
Permanent link

Direct link
The aperiodic broad-band X-ray variability of Cygnus X-3
Stockholm University, Faculty of Science, Department of Astronomy. (High-energy astrophysics)
(High-energy astrophysics)
(High-energy astrophysics)
Responsible organisation
2009 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 394, no 3, 1544-1550 p.Article in journal (Refereed) Published
Abstract [en]

We study the soft X-ray variability of Cygnus X-3. By combining data from the All-Sky Monitor and Proportional Counter Array instruments on the RXTE satellite with EXOSAT/Medium Energy (ME) detector observations, we are able to analyse the power density spectrum (PDS) of the source from 10−9 to 0.1 Hz, thus covering time-scales from seconds to years. As the data on the longer time-scales are unevenly sampled, we combine traditional power spectral techniques with simulations to analyse the variability in this range. The PDS at higher frequencies (≳10−3 Hz) are for the first time compared for all states of this source. We find that it is for all states well described by a power law, with index ∼−2 in the soft states and a tendency for a less steep power law in the hard state. At longer time-scales, we study the effect of the state transitions on the PDS, and find that the variability below ∼10−7 Hz is dominated by the transitions. Furthermore, we find no correlation between the length of a high/soft-state episode and the time since the previous high/soft state. On intermediate time-scales, we find evidence for a break in the PDS at time-scales of the order of the orbital period. This may be interpreted as evidence for the existence of a tidal resonance in the accretion disc around the compact object, and constraining the mass ratio to M2/M1≲ 0.3.

Place, publisher, year, edition, pages
2009. Vol. 394, no 3, 1544-1550 p.
Keyword [en]
accretion, accretion discs;stars: individual: Cyg X-3;X-rays: binaries
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-25520DOI: 10.1111/j.1365-2966.2009.14434.xISI: 000264820500030OAI: diva2:199889
Available from: 2008-10-09 Created: 2008-10-03 Last updated: 2011-02-24Bibliographically approved
In thesis
1. X-ray variability in Galactic high-mass black hole binaries
Open this publication in new window or tab >>X-ray variability in Galactic high-mass black hole binaries
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The stars of the night sky can to the naked eye appear to be steady and unchanging, apart from the twinkling created by air moving in the atmosphere. However, when viewed in X-rays, the sky is far from constant, with detectable changes occurring on very short timescales.

Black hole X-ray binaries are strong sources of X-rays. These systems contain a star and a black hole in orbit around each other. As matter from the companion star is accreted by the black hole, large amounts of gravitational energy are released, giving rise to strong X-ray emission. The accretion flow close to a black hole is characterized by strong gravity, high-energy radiation and variability on timescales down to milliseconds. These systems allow us to probe physics under conditions we cannot recreate in a laboratory, and provide some of the strongest observational indications of the existence of black holes. Temporal analysis is a powerful diagnostic of the geometry and physical processes of this environment.

The bulk of this thesis concerns studies of the rapid variability of perhaps the most well-known of all black hole binaries: Cygnus X-1. By tapping into the large amount of archival data available, a systematic study of the variability, in the form of the power spectrum, is conducted. The results show that timing studies can indeed give valuable information on the emission mechanisms and accretion geometry. Tying characteristic frequencies to effects predicted by general relativity directly gives information about the parameters of the compact object. Using these results, the past evolution of the binary system is studied.

In addition, results from temporal analysis of the possible black hole binary Cygnus X-3 are presented. The study of X-ray variability covers timescales from years to seconds, and shows that while temporal analysis provides clues to this complex system, it does not provide immediate insight into the accretion geometry, or the nature of the compact object

Place, publisher, year, edition, pages
Lidingö: Xvanen, 2008. 47 p.
Accretion, high-energy astrophysics, temporal variability, X-ray binaries
National Category
Astronomy, Astrophysics and Cosmology
Research subject
urn:nbn:se:su:diva-8245 (URN)978-91-633-3548-8 (ISBN)
Public defence
2008-10-30, Observatoriesalen, Observatoriemuseet, Drottninggatan 120, Stockholm, 14:00
Available from: 2008-10-09 Created: 2008-10-03Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Axelsson, MagnusLarsson, Stefan
By organisation
Department of Astronomy
In the same journal
Monthly notices of the Royal Astronomical Society
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 36 hits
ReferencesLink to record
Permanent link

Direct link