Super-orbital%20variability

1
Super-orbital variability in Cygnus X-1
ISSI, Bern, Switzerland March 3-7, 2008
J. Poutanen, A. Zdziarski, A. Ibragimov MNRAS,
submitted
2
Accretion via Roche lobe and focused wind

• Stream trajectory and disk formation for the case
  of equal masses.
• Coriolis force shifts the stream from the line
  connecting the stars.

3
Superorbital variability
Radio
X-rays
4
Dips distribution
5
Orbital profiles as a function of superorbital
phase
6
(c) A view from the top
bulge
? b
disc
supergiant
? 0.5
? 0
7
(a) A view along the orbital plane, ? 0
observer
i
bulge
?
supergiant
?
black hole
disc
? 0.5
? 0
8
(b) A view along the orbital plane, ? 0.5
observer
disc
supergiant
black hole
bulge
? 0.5
? 0
9
Model

• Wind
• Parameters inclination i40 deg
• Precession angle ?

• Bulge

Precession angle ? Optical depths bulge ?b,0 ,
wind ?w,0 Bulge azimuth ?b
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Model

• Emissivity profile of the accretion disk
• For the jet/ outflow

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Orbital profiles as a function of superorbital
phase
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Results
13
PDS of the model flux
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Conclusions

• Discovery of orbital modulation strength on
  superorbital phase of Cyg X-1
• Effect can be explained by the bulge displaced
  from the line connecting the stars by 25 deg.
• Distribution of dips is consistent with the model
• Beat-frequencies should be observed, with the
  stronger lower one.

15
Log-normal flux distribution