Xray pulsars: a view from

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X-ray pulsars a view from current cosmic
observatories
A.Lutovinov, S.Tsygankov Space Research
Institute, Moscow, Russia MPI for Astrophysics,
Garching, Germany
Blois 24 June 2009
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MNS1.5-3 ?sun RNS 10-15 km (106 sm) BNS
1012 G Pspin 1 103 s
Now 100 X-ray pulsars are known, usually in
binary systems with O-B spectral class massive
stars. A few in LMXB (e.g. Her X-1) Accretion of
matter via disk or stellar wind
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Name Type
P Porb
Companion
INTEGRAL totally observed more than 70 X-ray
pulsars during 7 years of the operation, discovere
d several new pulsars. 41 of them were detected
at the high significance level, that gave a
possibility to reconstruct their spectra
Combination with RXTE and XMM- Newton data new
results on physics of X-ray pulsars
OUTLINE Cyclotron line
energy dependence on the X-ray pulsars
luminosity Pulsed fraction dependence on the
luminosity and energy band
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Filippova, Tsygankov, Lutovinov, Sunyaev (2005)
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V033253
4U011563
Lx5x1037 erg/s Sharp shift of the cyclotron
energy occurs at the same luminosity
fundamental property of pulsar
Tsygankov, Lutovinov, Churazov, Sunyaev
(2006,2007)
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Accretion column structure
H few km
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Rising part of outburst (V 033253)
Outburst 2004-2005
Tsygankov et al. (2006), Tsygankov et al. (2009)

• Ecyc-0.14L3729.56 keV
• B((1z)/11.6)xEcycx1012 G3.5x1012 G

Ecyc1max 32 keV
ALL data
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Rising part of outburst (V 033253)
Outburst 2004-2005
Tsygankov et al. (2006), Tsygankov et al. (2009)

• Ecyc-0.14L3729.56 keV
• B((1z)/11.6)xEcycx1012 G3.5x1012 G

?
?
Ecyc1max 32 keV
ALL data
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Summary Ecycl vs Lx
Anti-correlation of the cyclotron line energy and
luminosity for V033253 and 4U011563 (?)
Tsygankov et al. (2006,2007,2009)
Her X-1 Correlation Staubert et al. (2007)
Complex behavior of the cyclotron line energy in
the A0535262 spectrum during the outburst
(Caballero et. al, 2008)
some evidences of similar behavior was registered
for GX301-2 (Filippova et al.2005) no evolution
of the cyclotron line for other sources,like Vela
X-1, Cen X-3, etc.
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II. Pulsed fraction dependence on the luminosity
and energy band
Timing analysis X-Ray data in narrow energy bands
gt Only bright sources Name Ecyc 4U
011563 11, 21, 34, 45 keV V 033253 28, 55
keV A 0535262 45, 100 keV Hercules X-1 38
keV Vela X-1 22, 56 keV GX 301-2 50 keV GX
14 34 keV (?) Cen X-3 31 keV OAO
1657-415 78 keV EXO 2030375 63 keV (?)
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Pulsed fraction dependence on the energy band
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Crab
for Crab-like spectrum
The increasing of the pulse fraction is a steeper
than we expect from our simple suggestion.
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X-ray pulsars
The situation is more complicated
Typical X-ray pulsars spectrum
corresponds to
Presence of cyclotron lines Absorption PF
dependence on the luminosity Different
mechanisms of the emission
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Toy model
Rotation axis is inclined in a such way that the
accretion column at one of the poles is seen
over its entire height, but only the upper part
emitting softer photons is seen in the second
column. Should be taking into account also a
light bending, possible reflection from the
neutron star surface and plasma on the Alfven
surface, beam function dependence from the
energy, etc.
Lutovinov,Tsygankov (2008)
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Pulsed fraction (4U 011563)
Tsygankov et al. (2007)
Schönherr et al. (2007)
Imax-Imin ImaxImin
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Summary

• Mostly accurate results of the spectral and
  timing analysis of several dozens X-ray pulsars
  in hard X-rays at the moment
• Strong dependence of the pulse fraction on the
  energy and source luminosity is revealed and
  study in detail
• The prominent feature in the dependence of the
  pulse fraction on energy band was revealed near
  the cyclotron frequency for several bright
  sources
• There are preliminary ideas how to explain above,
  but may be something else?...

Despite of 40 yr of X-ray pulsars observations
still there are many open questions Required new
generation of X-ray telescopes and
observatories NeXT, Spectrum-XG, XEUS -gt new
theoretical problems???