FROM SOFT TO HARD XRAY EMISSION

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FROM SOFT TO HARD X-RAY EMISSION PROPERTIES OF
ACCRETING X-RAY MILLISECOND
M A U R I Z I O F A L A N G A
Service dAstrophysique, CEA Saclay, France
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A Decade of Accreting millisecond X-ray Pulsars
SAX J1808.4-3658
Amsterdam, April 14 18, 2008
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Pulsar spin-up Animation
NASA, D. Barry
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OUTBURST PROFILE
XTE J1807-294
XTE J1807-294
From RXTE (Galloway et al. 2005)
ISGRI 20-100 keV
(Falanga et al. 2005)
(Falanga et al. 2005)
(Wijnands 2005, astro-ph/0403409)
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Outburst are extended as a consequence of X-ray
irradiation of the disk (King Ritter
1998)
Theory dwarf novae, SXT
XTE J1751-305
4U 1705-44
Hot viscose state
Rh lt Rdisc
SAX J1808.4-3658
Central object prevents the disk to cool down due
to Irradiation, on a viscous time-scale, accountin
g for the exponential decay of the outburst on a
timescale t2040 d.
(Powell, Haswell Falanga, 2007)
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OUTBURST PROFILE
HETE J1900.1-2455
(Falanga et al. 2007)
After 60 days Period disappeared
(Kaaret, et al. 2007)
NEW Intermittent Pulsation
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HETE J1900.1-2455
(Falanga et al. 2007
(Galloway et al. 2007
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Pulsed Fraction
(Piro Bildsten 2007
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The growing family of the X-ray millisecond
pulsars
now we know 8 LMXBs (transients) which show
X-ray millisecond coherent modulation

• SAX J1808.4-3658 Ps 2.5ms, Porb 2hr
  (Wijnands van der Klis 1998)
• XTE J1751-306 Ps 2.3ms, Porb 42min
  (Markwardt et al. 2002)
• XTE J0929-314 Ps 5.4ms, Porb 43.6min
  (Galloway et al. 2002)
• XTE J1807-294 Ps 5.3ms, Porb 40min
  (Markwardt et al. 2003)
• XTE J1814-388 Ps 3.2ms, Porb 4.3hr
  (Markwardt et al. 2003)
• IGR J002915934 Ps 1.67ms, Porb 2.46hr
  (Eckert et al. 2004)
• HETE J1900.1-2455 Ps 2.65ms, Porb 1.4hr
  (Markwardt et al. 2005)
• Swift J1756.9-2508 Ps 5.49ms, Porb 54.7min
  (Krimm et al. 2007)

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INTEGRAL Observation IGR J002915934
December 2004 Outburst Exposure 343 ks
IGR J002915934
2S0114650
Cas Gamma
Cas A
V709 Cas
(20 - 40 keV)
(20-40 keV) significance level 88s derived
angular distance 18
(40-80 keV) significance level 51s (80-200
keV) significance level 17s
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Geometry of the emission region
The plasma is heated by the accretion shock as
the material collimated by the hotspot on to the
surface. The seed photons for Comptonization are
provided by the hotspot.
?
B 108 G
Seed photons from the hotspot
Thermal Comptonization in plasma of Temperature
40 keV
XTE J1807-294
Rm
Thermal disk emission
(Falanga, Bonnet-Bidaud, Poutanen et al. 2005)
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Spectral energy distribution
Gierlinski Poutanen 2003
Poutanen Gierlinski 2001
spot
kTbb 0.66keV kTe 60 keV tT 0.9
disc
XTE J1751-305
Falanga et al 2007
Falanga et al 2005
HETE J11900.1-2455
IGR J002915934
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Spectral evolution
IGR J002915934
XTE J1751-305
Gierlinski Poutanen 2003
Falanga et al. 2005
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PULSE PROFILE
IGR J002915934
Rev 261/262/263, 205 Porbit 2.457 hr Ps 1.67
ms Pdot 8.4 x 10-13 Hz/s
(Falanga, Kuiper, Poutanen et al. 2005)
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Pulsed fraction and Time lag IGR J002915934
(Falanga, Kuiper, Poutanen et al. 2005)
(Falanga et al. 2005)
If the spectrum has a sharp cutoff, the rms
amplitude of the pulse at energies above the
cutoff increases dramatically.
F(E) E-(G0-1) exp(-E/Ecß),Componization photon
index G(E) G0 ß(E/Ec)ß
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Time lag
Comptonization model (Cui et al. 1998) vs. GR
model (Ford 2000)
Soft time lag Downscattering of hard photons vs
GR Doppler boosting
Soft time lag Combination of Comptonization and
GR Doppler boosting effects (Poutanen, 2001)
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Time lag
(Falanga et al. 2005)
IGR J002915934
Compton scattering model
The energy spectra often observed in LMXBs
suggests that the dominant radiative mechanism in
the system is Compton scattering of soft photons
in a hot plasma.
(For a review of models for spectral variability
and time lags see Poutanen 2001)
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(Falanga Titarchuk 2007)
Time/Phase Lag Model
?t(Cill,?ref,?hot,neref,nehot) upscattering
lag downscattering lag
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Some Questions

• Missing link between LXMB and ms radio pulsar ?
• Hard X-ray observations for spectral and timing
  is important.
• Study the emission geometry using also hard
  X-ray data

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Thank You