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High energy behaviour of Neutron Star Low Mass X-ray Binaries seen by INTEGRAL

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:

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High energy behaviour of Neutron Star Low Mass X-ray Binaries seen by INTEGRAL

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  1. 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

  2. The Low Mass X-ray Binaries Emission processes: 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. • Accretion by Roche Lobe overflow • Companion star: • Late type (> A), pop II • mass M<2Mʘ • Lx/Lott~100-1000 • Orbital Period ~ 10 m-10 d • Rare eclipses and X pulsation HMXB LMXB  old systems located in the Galactic Bulge • Accretion disk black body (thermal) • Corona  Comptonization • Reflection reflected emission by the accretion disk • Jet ? non-thermal emission (synchrotron emission)

  3. Burster and Atoll sources Type-1 X-ray bursts sources: • 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 Cornelisse et al.2001 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

  4. Open Issues on NS LMXBs Fender, Belloni, Gallo 2004 • 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 NS-BH exist? Are the bursters lower luminous than Black Hole Binaries? Bursters Box? Migliari et al 2006 Barret et al. 1996, 2000

  5. IBIS survey populations Galactic Buldge deep exposure along the INTEGRAL operative life is welll represented by the increasing LMXB population Bird et al. 2009

  6. LMXB/BURSTERS population Cat 1 29 Cat 4 50 Bursters account for 55% of the firm LMXB IN Cat 4 Since the beginning INTEGRAL discovered 5 new bursters and 1source 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 type-I X-ray burst emission

  7. Atoll sources analised in detail • 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

  8. Spectral state transitions

  9. 4U 1608-522 • IBIS and JEM-X: I= (10-20 keV)+(20-30 keV) Hard Color= (20-30 keV/10-20 keV) • JEM-X: I= (4-10 keV)+(10-20 keV) Hard Color=(10-20 keV/ 4-10 keV) • Observation period February 2004 – September 2006 • Outburst: February – June 2005 Transient source Tarana et al. ApJ 2008

  10. Tarana et al. ApJ 2008 kTe = 7 keV, τ=1.7 kT0 =1.2 keV kTin= 0.7 keV Spectral variation 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 kTe = 3.5 keV,τ=3.4 kT0 =1.1 keV kTin= 0.6 keV Increasing Rin decreases kTe = 3.0 keV, τ=4.1 kT0 =1 keV kTin= 0.5 keV L bol=6·1037 erg s-1

  11. 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

  12. 4U 1722-30 kTe=2.2 keV, τ=9.1, kT0=0.4 keV kTin=0.5 keV Soft state: CompTT+ diskbb Hard/Interm. state:CompTT+diskbb Hard state: CompTT kTe=11.4 keV, τ=1.3, kT0=1.3 keV kTin=0.54 keV kTe=40 keV, τ=0.5, kT0=0.8 keV

  13. 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 1st 2nd 3th

  14. Spe Box 3 GX 354-0 Spe Box 1 Spe Box 6 CompTT+diskbb: kT0~1 keV kTe ~8 keV ~2.6 kTin~1 keV CompTT+diskbb: kT0~1 keV kTe ~3 keV ~6 kTin~1 keV Hard State with power law tail! CompTT+diskbb+PL: kT0~1 keV kTe ~9.7 keV ~3.1 kTin~1 keV ~ 1.8

  15. 4U 1820-30 • Ultracompact sistem, P=685 s • In the Globular Cluster NGC 6624. • Hard color- Intensity diagram: JEM-X (4-10 and 10-20 keV) • 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 4-10 keV 20-30 keV Tarana et al. ApJ 2007

  16. CompTT: kTe ~2-3 keV ~6-7 kT0~0.2-0.4 keV CompTT+PL: kTe ~6 keV ~4 kT0~1.5 keV ~ 2.4 Other model for the Hard State: Comptonization (CompPS) with hybrid thermal-non thermal population of the electrons Hard Tail

  17. New “Busters Box” Lhard The ratio R= 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: 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 Soft states Lsoft

  18. …adding Persistent sources: Lhard Persistent sources with L derived from the average spectra from the IBIS survey: 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 1.5 1037 erg s-1 Hard states Soft states Lsoft

  19. Conclusions • Burters are confirmed high energy emitters • Two type of hard spectral state from Atoll: • Comptonized emission with no evident cut-off-energy • 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

  20. Type - 1 X-ray bursts: blackbody with kTbb 1.9-3.1 keV 4U 1812-12 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 Tarana et al. A&A 2006

  21. Stato Hard Stato Soft

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