Neutron Star Star Low Low Mass Mass Neutron Neutron Star Low - PowerPoint PPT Presentation

High High energy astrophysics summer school energy astrophysics summer school Urbino 28 July- Urbino 28 July- 1August 2008 1August 2008 Neutron Star Star Low Low Mass Mass Neutron Neutron Star Low Mass X-ray Binaries X-ray Binaries X-ray Binaries (NSLMXBs NSLMXBs) ) seen by seen by ( (NSLMXBs) seen by INTEGRAL: high energy energy INTEGRAL: high INTEGRAL: high energy behaviour behaviour behaviour Antonella Tarana Tarana Antonella In In collaboration collaboration with: with: • • l l’ ’IBIS TEAM ( IBIS TEAM (IASF-Roma IASF-Roma, INAF): A. , INAF): A. Bazzano Bazzano, P. , P. Ubertini Ubertini, F. , F. Capitanio Capitanio, G. De , G. De Cesare, M. Fiocchi, L. Natalucci Natalucci, M. Del Santo, M. , M. Del Santo, M. Federici Federici Cesare, M. Fiocchi, L. 1 1 • A.A. A.A. Zdziarski Zdziarski, D. , D. Gotz Gotz, T. , T. Belloni Belloni •

Outline Outline  The INTEGRAL The INTEGRAL Laboratory Laboratory   The The Galactic Survey Galactic Survey   Low Low Mass Mass X-ray Binaries X-ray Binaries, , Bursters Bursters and Atoll and Atoll sources sources   Emission processes Emission processes   INTEGRAL INTEGRAL contribution contribution on on understanding NSLMXBs understanding NSLMXBs (>20 keV) (>20 keV)   LMXBs spectral variability study with LMXBs spectral variability study with INTEGRAL: some INTEGRAL: some  example example  Our Our Project: the Project: the source selected source selected and and aims aims. .  2 2

INTEGRAL INTEGRAL INTEGRAL ( INTEGRAL ): launched launched on on October October 17th 2002, 17th 2002, (INTErnational Gamma-Ray Laboratory INTErnational Gamma-Ray Laboratory):   elliptic orbit lasting about 3 3 days days. . elliptic orbit lasting about IBIS ( IBIS (Imager Imager on Board the INTEGRAL satellite) on Board the INTEGRAL satellite)   Energy range range: 15 keV - 10 : 15 keV - 10 MeV MeV Energy   FOV: 29° FOV: 29 °x29 x29° ° (9 (9° °x9 x9° ° fully coded fully coded) )   Angular resolution: 12 Angular resolution : 12’ ’   Sensitivity (3 sigma,1Ms): 2.3 (3 sigma,1Ms): 2.3· ·10 10 -6 -6 ph ph cm cm -2 -2 s s -1 -1 keV keV -1 -1 @ 100 keV @ 100 keV Sensitivity   JEM-X JEM-X   Energy range range: 3-35 keV : 3-35 keV Energy   FOV= 13.2 FOV= 13.2° °x13.2 x13.2° °   (4.8° °x4.8 x4.8° ° fully coded fully coded) ) (4.8 Angular resolution: 3 : 3’ ’ Angular resolution   Sensitivity (3 sigma, 1Ms): (3 sigma, 1Ms): Sensitivity   10 -5 -5 ph cm -2 -2 s s -1 -1 keV keV -1 -1 @ 6 keV 1.3 1.3 · ·10 ph cm @ 6 keV 3 3

INTEGRAL INTEGRAL Coded mask instruments: the : the Coded mask instruments   signal must be decodified. . signal must be decodified All All the the sources sources of the of the Field Field Of Of   View View (FOV) (FOV) must be must be identified identified. . 4 4

INTEGRAL INTEGRAL From October 2002 2002 to today to today: :  From October  Revolution #705  Revolution #705  About 60000 60000 pointings pointings ( (ScWs ScWs) ) lasting lasting 2000-3600 2000-3600  About  seconds each. . seconds each At IASF-Rome IASF-Rome more more than than 4 4 tera tera byte of data byte of data  At  Third IBIS IBIS Galactic Survey Galactic Survey (first 3.5 (first 3.5 years years) ( ) (Bird Bird  Third  et al. 2007): al. 2007): about about 460 460 sources sources! ! et 21% transient transient, 79% , 79% persistent persistent: : for for the the persistent persistent  21%  sources we can can use use the the mosaic mosaic of of all observations all observations! ! For For sources we the transient sources we must transient sources we must do a more do a more detailed detailed the pointing study. . pointing study 5 5

Sky coverage Sky coverage 6 6 All-sky galactic projection - contours at 500ks intervals Cat 1 Cat 2 Cat 3

Sources population Sources population SNR Unknown 2% 19% AGN Pulsars 32% 3% LMXB 21% CV 5% HMXB 18% 7 7

Sources distribution Sources distribution 8 8

The Low Low Mass Mass X-ray Binaries X-ray Binaries The X-ray Binaries: X-ray Binaries : systems composed by systems composed by a a normal normal star and a compact star (BH, NS and WD). star and a compact star (BH, NS and WD). . tranfer phenomena . X-ray emission at L at L X ~10 37 37 erg s erg s -1 -1 due to mass due to mass tranfer phenomena X-ray emission X ~10 Accretion by Accretion by Roche Roche Lobe overflow Lobe overflow   Companion star: star: Companion   HMXB LMXB HMXB LMXB  Late type Late type (> A), pop II (> A), pop II  _  mass M<2M mass M<2M _  L x /L ott ~100-1000 L x /L ott ~100-1000   Orbital Period ~ ~ 10 m-10 d 10 m-10 d Orbital Period   Rare eclipses Rare eclipses and X and X pulsation pulsation    old old systems systems   located located in the in the  Galactic Bulge Galactic Bulge Emission processes: : Emission processes Accretion disk disk   black body ( black body (thermal thermal) ) Accretion   Corona   Comptonization Comptonization Corona   Reflection Reflection   reflected emission by reflected emission by the the   accretion disk disk accretion Jet ?   non-thermal emission non-thermal emission Jet ?   (synchrotron emission synchrotron emission) ) ( 9 9

Burster and Atoll and Atoll sources sources Burster Type-1 X-ray bursts sources X-ray bursts sources: : Type-1 Cornelisse et al.2001 - -Recurrent X-ray peak emission Recurrent X-ray peak emission ) with E ~10 39 39 erg (range E=0.1-40 (range E=0.1-40 keV keV) with E ~10 erg - Fast rise (~ 1 s) and exponential decay - Fast rise (~ 1 s) and exponential decay - Cooling black body spectra during the decay - Cooling black body spectra during the decay Thermonuclear Thermonuclear flash flash on the NS on the NS surface surface The compact objects objects are are  The compact  NEUTRON STARs NEUTRON STARs Atoll sources sources: : Atoll • “ “Atoll Atoll” ” track in the Color-Color track in the Color-Color • Diagram (CCD) Diagram (CCD) Different spectral spectral and timing and timing • Different • properties in the different in the different properties branches of the CCD of the CCD branches  Sources Sources with with spectral spectral  state state variations variations 10 10

Barret et al. 1996, 2000 Why the high the high energy emission study energy emission study? ? Why Open questions questions in the in the physics physics of of Open   NS LMXBs LMXBs, , Atoll Atoll: : NS  Thermal high energy emission: :  Are the Are the bursters lower bursters lower  luminous than Black Black Hole Hole luminous than Binaries? ( ? (Bursters Bursters Box Box?) ?) Binaries  Have the Have the Bursters Bursters different different  spectral state state parameters parameters spectral respect to the Black to the Black Hole Hole respect Binaries? Binaries ?  Non-thermal emission: what is what is Di Salvo & Stella 2001 the origin origin of the hard of the hard power law the tails? ?  Does Does Radio-X ray connection  exist also for Atoll as for BH exist also for Atoll as for BH and Z sources and Z sources? ? Accretion processes physics Accretion processes physics   Differences Differences and and similarities similarities with with   BHCs and and AGNs AGNs. . BHCs 11 11 Migliari et al 2006 Fender, Belloni, Gallo 2004

NSLMXBs observed by NSLMXBs observed by INTEGRAL: some example example INTEGRAL: some 12 12

IBIS/INTEGRAL “ “mosaic mosaic” ” image image (20-100 keV) (20-100 keV) IBIS/INTEGRAL 13 13

4U 1820-30 4U 1820-30 Ultracompact sistem Ultracompact sistem, P=685 s , P=685 s   In the Globular Cluster Globular Cluster NGC 6624. NGC 6624. In the   Ligth curves ASM, JEM-X and IBIS: March ASM, JEM-X and IBIS: March  2003 - October October 2005 2005 2003 - Hard color- Intensity  Period A: max Flux Period A: max Flux in the 4-10 keV band, in the 4-10 keV band, ~ ~ diagram:   530 mCrab 530 mCrab; period C ; period C min Flux min Flux in the 4-10 keV in the 4-10 keV JEM-X (4-10 and 10-20 keV) JEM-X (4-10 and 10-20 keV) band, ~ ~ 100 100 mCrab mCrab band, 4-10 keV 20-30 keV 14 14 Tarana et al. ApJ 2007

Soft states states Soft Tarana et al. ApJ 2007 ? All the Soft spectra are modelled with Comptonization model model: Comptonization CompTT (Titarchuk 1994) with kT e 2-3 keV keV, optical depth optical depth kT ~ 2-3 e ~ 6-7 and and k k T . ̃ 6-7 0.2-0.4 keV . T 0 ~0.2-0.4 keV 0 ~ ̃ Maximum bolometric Luminosity 7.7 _10 37 erg s -1 (assuming d=5.8 kpc) 15 15

Hard State Hard State Spectral model CompTT CompTT+ power + power law law :  Electron temperature, kT e = 6 keV, temperature of input photons, kT 0 1.5 keV and corona optical depth, _ = 4;  Power law with photon index, _ = 2.4 Tarana et al. ApJ 2007 Hard Tail? Fender 2000 Bloser et al 2000 16 16