Longterm Periodicities and Accretion Disk Warping

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Longterm Periodicities and Accretion Disk Warping
Will Clarkson Phil Charles Silas Laycock Malcolm
Coe Colleen Wilson-Hodge Martin Tout
Figure from Wijers Pringle, 1999 MNRAS 308, 207
Will Clarkson University of Southampton
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The Importance of Warping

• (Precessing) disk warps are becoming ubiquitous

Microquasars
Hjellming Johnston, 1981 ApJ 246, L141
Galliano Alloin 2002 AA 393, 43
AGN
4885 MHz VLA maps of SS433
NGC 1068 with VLT/ISAAC
YSOs
Launhardt Sargent, 2001 ApJ 562, L173
Galactic Disks
NASA / Stsci
Warped Spiral Galaxy ESO 510-G13
CO (10) emission from Bok Globule BC26
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Longterm X-ray Periodicities

• 20 XRB exhibit X-ray Plong gt 10 days
• By comparison, Porb typically lt few days (unless
  Be/symbiotic)
• Pspin, PQPO 1ms 1ks, Pflicker 1s 1hr
• Some examples from ns/bhc XRB
• Seen with X-ray All Sky Monitors, e.g Ariel 5,
  BATSE, RXTE

Neutron Star XRB Her X-1 35d LMC X-4 30d SMC
X-1 50-70d Cyg X-2 50-80d
Black Hole XRB SS433 160d LMC X-3
99d 4U195711 117d GX339-4 190-250d

• Can disk warping reproduce these periodicities?

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An example XRB warper Her X-1

• Strongly suspected of disk warping and precession
• Long-documented 35-d on-off X-ray cycle
• Photometric variations on (Plong , Porb) beat
  period
• Precessing disk suggested (Gerend Boynton 1976)

Longterm X-ray lightcurve
RXTE/ASM (NASA) Jan 1996 present 1.3-12.0
keV 10 readings per day
1.3-12.0 keV spectral hardness
1.3-12.0 keV flux (RXTE/ASM)
Phase (35d cycle)
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Warping Mechanism

• Tidal effects of companion ? disk precession
• (Katz 1973) independent ring elements precess
  gyroscopically

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Evolution of Her X-1 periodicity

• Dynamic power spectrum and lightcurve

Lightcurve
Power Spectrum
600
LS Power
RXTE/ASM c/s
0
2002
2002
Time
Time
1996
1996
0 0.5 1.0 1.5
2.0
100 50 33 20 15
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Phase
Frequency (days)
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Further Disk Warpers

• Three ns XRB are suspected of warping and
  precession

SMC X-1
Cyg X-2
LMC X-4
Lightcurves from RXTE / ASM Each plot spans 250
days
Her X-1
r_crit sensitive to ? and ?
Figure from Ogilvie Dubus 2001 MNRAS 320, 485
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Arrangement with r_b

• Schematic illustration of radiation-driven warp
  predictions

Precession frequency
Binary separation
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Conclusion and Questions

• Radiation-driven warping correctly predicts
  qualitative superorbital X-ray behaviour for
  persistent neutron star XRB
• Clarkson, Charles, Laycock, Coe 2003 MNRAS ,
  astro-ph/0304073
• Disk thickness deviations from Ogilvie Dubus
  2001?
• Reaction to irradiation should be f(z)
• What about non-ns systems?
• SS 433 160-d X-ray lightcurve may require disk
  warp
• Clarkson Charles 2003 MNRAS in prep
• Exactly how is the warp manifested?
• SMC X-1 shows signs of varying Lx, not
  obscuration
• Clarkson, Charles, Laycock, Coe, Wilson, Tout
  2003 MNRAS 339, 447
• Cen X-3 shows no correlation between Lx and spin
  period in its 6 month cycle
• Tsunemi, Kitamoto Tamura, ApJ 1996, Clarkson,
  Charles, Hambidge, Richardson, Wilson 2003 in prep

• Longterm X-ray behaviour ? system constraints?