Transcript High energy behaviour of Neutron Star Low Mass X

Seven years of INTEGRAL
“The extreme sky: Sampling the Universe above 10 keV”
High energy behaviour of
Neutron Star Low Mass X-ray
Binaries seen by INTEGRAL
Antonella Tarana
(IASF-Roma INAF)
In collaboration with:
• l’IBIS TEAM (IASF-Roma, INAF): A. Bazzano, P. Ubertini, F.
Capitanio, G. De Cesare, M. Fiocchi, L. Natalucci
• A.A. Zdziarski, T. Belloni
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The Low Mass X-ray Binaries
X-ray Binaries: systems composed by a normal star and a compact star (BH, NS and WD).
X-ray emission at LX~1037 erg s-1 due to mass tranfer phenomena.
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HMXB
LMXB
Accretion by Roche Lobe overflow
Companion star:
• Late type (> A), pop II
• mass M<2Mʘ
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Lx/Lott~100-1000
Orbital Period ~ 10 m-10 d
Rare eclipses and X pulsation
 old systems located in the
Galactic Bulge
Emission processes:
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Accretion disk  black body (thermal)
Corona  Comptonization
Reflection  reflected emission by the
accretion disk
Jet ?  non-thermal emission
(synchrotron emission)
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Burster and Atoll sources
Type-1 X-ray bursts sources:
Cornelisse et al.2001
- Recurrent X-ray peak emission
(range E=0.1-40 keV) with E ~1039 erg
- Fast rise (~ 1 s) and exponential decay
- Cooling black body spectra during the decay
Thermonuclear flash on the NS surface
 The compact objects are
NEUTRON STARs
 Distance extimation
Atoll sources:
• “Atoll” track in the Color-Color
Diagram (CCD)
• Different spectral and timing
properties in the different
branches of the CCD
Sources with spectral
state variations
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Open Issues on NS LMXBs
Fender, Belloni, Gallo 2004
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How many Bursters are
characterized by hard X-ray
emission?
INTEGRAL Deep Survey solve it
• What about high energy spectral
state transitions
 two types of Hard state in the
Atoll appear
• Hard tail from Atoll source?  yes
– Disc-jet connection
– Thermal-non thermal
composition of the electrons
corona
• Does a method to distinguish NSBH exist? Are the bursters lower
Migliari et al 2006
luminous than Black Hole
Binaries? Bursters Box?
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Barret et al. 1996, 2000
IBIS survey populations
Galactic Buldge deep exposure along the INTEGRAL
operative life is welll represented by the increasing LMXB
population
Bird et al. 2009
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LMXB/BURSTERS population
Cat 1
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Cat 4
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Bursters account for 55% of the firm LMXB IN Cat 4
Since the beginning INTEGRAL discovered 5 new
bursters and 1 source has been identified because of
burst detection (Del Santo et al. 2007).
This is not surprising if compare to the BeppoSAX/WFCs
new detections (14) because of the lower energy band of
WFCs (2-28 keV) respect to IBIS, more compatible with
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type-I X-ray burst emission
Atoll sources analised in detail
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–
4U 1812-12 P
4U 1820-30
V R GC
4U 1728-34
V R
T
4U 1608-522 V R
T
XB 1832-330 P
GC
4U 1254-690 V
D
4U 1722-30
V
GC
P= persistent sources
D= dipper
V= variable sources
R= radio counterpart
GC=Globular Cluster sources
T= transient sources
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Spectral state transitions
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4U 1608-522
Transient source
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Observation period February 2004 –
September 2006
Outburst: February – June 2005
Tarana et al. ApJ 2008
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IBIS and JEM-X:
I= (10-20 keV)+(20-30 keV)
Hard Color= (20-30 keV/10-20 keV)
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JEM-X:
I= (4-10 keV)+(10-20 keV)
Hard Color=(10-20 keV/ 4-10 keV)
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Tarana et al. ApJ 2008
Spectral
variation
kTe = 7 keV, τ = 1.7
kT0 =1.2 keV
kTin= 0.7 keV
Hard State:
HIGH electrons temperature!
kTe= 60 keV, τ =0.4,
kT0 =1.2 keV
kTin= 0.4 keV
L bol=5·1037 erg s-1
Increasing Rin
 decreases
m
kTe = 3.5 keV,τ = 3.4
kT0 =1.1 keV
kTin= 0.6 keV
kTe = 3.0 keV, τ = 4.1
kT0 =1 keV
kTin= 0.5 keV
L bol=6·1037 erg s-1
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4U 1722-30
Observation peridod: October 2003- April 2005
Ligth curves: ASM, JEM-X and IBIS.
Color-intensity diagrams with IBI-JEM-X and
JEM-X only
Tarana et al. 2008 PoS
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4U 1722-30
Soft state:
CompTT+
diskbb
Hard state: CompTT
kTe=40 keV, τ=0.5, kT0=0.8 keV
kTe=2.2 keV,
τ=9.1,
kT0=0.4 keV
kTin=0.5 keV
Hard/Interm. state: CompTT+diskbb
kTe=11.4 keV, τ=1.3,
kT0=1.3 keV
kTin=0.54 keV
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GX 354-0: INTEGRAL-RXTE monitoring
RXTE: AO11 2 ks pointings every two days March 2006- June 2007
INTEGRAL: Galactic Centre Deep Exposure: February - April 2006
AO4 Key Programme + General program: August-October 2006 February-April 2007
st
1
nd
2
th
3
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Spe Box 3
GX 354-0
CompTT+diskbb:
CompTT+diskbb:
kT0~1 keV
kTe ~3 keV
~6
kTin~1 keV
kT0~1 keV
kTe ~8 keV
~2.6
kTin~1 keV
Hard State with power law tail!
Spe Box 1
Spe Box 6
CompTT+diskbb+PL:
kT0~1 keV
kTe ~9.7 keV
~3.1
kTin~1 keV
~ 1.8
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4U 1820-30
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Ultracompact sistem, P=685 s
In the Globular Cluster NGC 6624.
Ligth curves ASM, JEM-X and IBIS: March 2003 October 2005
Period A: max Flux in the 4-10 keV band, ~ 530
mCrab; period C min Flux in the 4-10 keV band, ~
100 mCrab
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Hard color- Intensity
diagram:
JEM-X (4-10 and 10-20 keV)
4-10
keV
20-30
keV
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Tarana et al. ApJ 2007
CompTT:
Other model for the Hard State:
Comptonization (CompPS) with
hybrid thermal-non thermal
population of the electrons
Hard Tail
kTe ~2-3 keV
~6-7
kT0~0.2-0.4 keV
CompTT+PL:
kTe ~6 keV
~4
kT0~1.5 keV
~ 2.4
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New “Busters Box”
The ratio R=
Lhard
Lsoft /Lhard
is:
–
7— 56 for the Soft
spectral state
– 0.4— 4 for the Hard
spectral state
1.5 1037 erg s-1
Hard states
Soft states
Lsoft
Soft: Lsoft > 6 · 1036 erg s-1
Lhard<1.4 · 1036 erg s-1
Hard: Lsoft < 6 · 1036 erg s-1
Lhard>0.7 · 1036 erg s-1
Hard state with power law:
Lsoft ~ 5 · 1036 erg s-1
Lhard>4 · 1036 erg s-1
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…adding Persistent sources:
Persistent sources with L
derived from the average
spectra from the IBIS survey:
Lhard
1.5 1037 erg s-1
Hard states
Soft states
Lsoft
4U 1746-37
XTE J1701-281
4U 1705-32
IGR J17254-3257
4U 1246-58
GX 17+2
4U 1708-40
Cyg X-2
GX 3+1
SLX 1735-269
SLX 1744-299
GX 13+1
Ser X-1
Cir X-1
4U 1916-053
4U 0918-54
SLX 1737-282
EXO 0748-676
4U 1323-62
4U 1850-087
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Conclusions
• Burters are confirmed high energy emitters
• Two type of hard spectral state from Atoll:
– Comptonized emission with no evident cut-offenergy
– Hard tail: Power law / hybrid thermal-non thermal
composition of the electrons corona
• Burters Box information:
– Lhard limit respected
– Same spectral state at different luminosity
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4U 1812-12
Type - 1 X-ray bursts:
blackbody with kTbb 1.9-3.1 keV
Persistent emission:
black body (Sakura & Sunyaev 1973) + CompTT
(Titarchuk 1994) and NH =1.5 · 1022 cm-2.
F1-100 keV =9.1·10-10 erg s-1 cm-2.
L bol.=2·1036 erg s-1 (with d=4.2 kpc) = ~1% L
Edd (with MNS=1.4 Mʘ)
Continuum and bursts emission:
kTe = 18 keV
τ=2
T0=0.3
kTbb= 0.6 keV
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Tarana et al. A&A 2006
Stato Hard
Stato Soft
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