X-ray pulsars through

1
X-ray pulsars through the eyes of INTEGRAL
A.Lutovinov, S.Tsygankov (IKI) the discussion
with J.Poutanen, M.Revnivtsev and V.Suleimanov
Funasdalen 2008
2
OUTLINE (What is a new in hard X-rays)I. Hard
X-ray spectra of X-ray pulsars II. Cyclotron
line energy dependence on the X-ray pulsars
luminosity III. Pulse profiles dependence on
the luminosity and energy band IV. Pulse
fraction dependence on the luminosity and energy
band
3
Name Type
P Porb
Companion
INTEGRAL totally observed more than 70 X-ray
pulsars during 5 years of the operation, discovere
d several new pulsars. 38 of them were detected
at the high significance level, that gave a
possibility to reconstruct their spectra
4
Filippova, Tsygankov, Lutovinov, Sunyaev (2005)
5
V033253
High state a -0.09/-0.01 Ecut 9.15/-0.03
??? Ecyc1 26.21/-0.15 ??? Ecyc2 50.66/-0.3
??? Ecyc3 73.8/-1.8 ??? Ecyc1/Ecyc2/Ecyc3
1/1.93/2.82
Tsygankov, Lutovinov, Churazov, Sunyaev (2006)
6
The cyclotron line energy dependence on the
source luminosity
Ecyc-0.1L3729.0 keV
B((1z)/11.6)xEcycx1012 G3x1012 G
7
Accretion column structure
(Lyubarskyi, Sunyaev, 1982)
H few km
8
X-ray outbursts of 4U 011563
Spectral parameters a 0.09/-0.01 Ecut
8.9/-0.1 keV Ecyc1 11.16/-0.03 keV Ecyc2
21.2/-0.1 keV Ecyc3 34.6/-0.2 keV Ecyc4
44.9/-0.3 keV Ecyc1/Ecyc2/Ecyc3/Ecyc4
1/1.9/3.1/4.0
Ecyc3
Ecyc1
Ecyc4
Ecyc2
Tsygankov, Lutovinov, Churazov, Sunyaev (2007)
9
The cyclotron line energy dependence on the
source luminosity
Lx5x1037 erg/s Sharp shift of the
cyclotron energy occurs at the same luminosity
the fundamental property of pulsar (?)
10
A053526
KS1947300
Disk accretion (Ghosh,Lamb 1978)
Tsygankov, Lutovinov (2005)
Tsygankov, Lutovinov (2008)
11
Luminosity and energy dependence of pulse
profiles (V033253 example)
12
Evolution of pulse profiles near the main
cyclotron line harmonic
6?1037 erg/s
2.6?1038 erg/s
Ecycl
13
3D- and 2D-pulse profile variations
Tsygankov, Lutovinov, Churazov, Sunyaev (2006)
14
Her X-1
Vela X-1
There is catalog of hard pulse profiles of 10
bright X-ray pulsars, their dependences on the
energy, luminosity, orbital phases, etc. Soon on
the web!
15
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. See e.g. poster Annala Poutanen
16
Pulse fraction dependence on the luminosity and
energy band
Timing analysis of the INTEGRAL/IBIS data of
X-ray pulsars in narrow energy bands. Only
bright sources (flux in the 20-50 keV range gt100
mCrab) 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 - Cen X-3 31
keV OAO 1657-415 78 keV (not detected with
INTEGRAL) EXO 2030375 -
17
Pulse fraction dependence on the energy
Also for millisecond pulsars (Falanga 2007)
18
Crab
for Crab-like spectrum
The increasing of the pulse fraction is a steeper
than we expect from our simple suggestion.
19
X-ray pulsars
The situation is more complicated
Typical X-ray pulsars spectrum
corresponds to
Presence of cyclotron lines PF dependence on
the luminosity Different mechanisms of the
emission
20
PF vs I(E)-1
A(E) - non-universal and different for different
X-ray pulsars
21
Preliminary ideas
The rise of the amplitude in the exponential
tail Temperature grows towards deeper
layers At higher inclinations - cooler outer
layers At lower inclinations hotter deeper
layers are visible The intensity in the Wien
tail will be strongly modulated The rise of the
amplitude in the cyclotron line A strong
dependence of the opacity on the angle with
the magnetic field can give a large modulation.
22
Summary

• Mostly accurate results of the spectral and
  timing analysis of several dozens X-ray pulsars
  in hard X-rays at the moment
• The evolution of the cyclotron energy with the
  source luminosity was studied in detail for the
  first time. It was shown that for V033253 and
  A53526 this dependence is linear, but for
  4U011563 is more complicated
• 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?...