T ransient NS X -ray binaries with S imbol- X
description
Transcript of T ransient NS X -ray binaries with S imbol- X
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Transient NS X-ray binaries with
Simbol-X
Sergio Campana Osservatorio astronomico
.itBologna, May 2007
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Outline
RXTE/ASM light curve
A brief history: what we discovered and what we know now, focusing of hard X-ray emission
The future: Simbol-X
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X-ray binaries: variable
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State transitions: SIGMA
Barret & Vedrenne 1994
Limiting luminosity for all LMXRBs (NS+BH) at 4x1036 erg/s
Maccarone 2003
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Campana et al. 1998
Hard tails: INTEGRAL
Tarana et al. 2007
4U 1820-30
Paizis et al. 2006
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BH XRB
NS XRB
Homan et al. 2007
State transitions: jets
Belloni 2007
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Campana et al. 1998 Di Salvo et al. 2000
Farinelli et al. 2007
Occasional detection of very hard tails (BMC)
GX 17+2
Very hard tails: PDS/XTE
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From outburst to quiescence
FAST !
e-folding time changing from ~20 d to ~1 d at transition
BeppoSAX data
Campana et al. 1998
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NS transients in quiescence
Canonical spectrum: Soft component (NS atmosphere, kT~0.1-0.3 keV; ≥50% of the flux)
Hard component (Power law, photon index ~1-2; ≤50% of the flux)
ExN
(E)
ExN
(E)
Lx=1032-1033 erg/s
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NS transients in quiescence: variability
Campana et al. 2003 Rutledge et al. 2001Campana &Stella 2004
Aql X-1
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Transient X-ray pulsars
Campana et al. 2007
Wijnands 2005
SAX J1808.4-3658
mcr
ab
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SAX J1808.4-3658 in quiescence
NS atmosphere model can account less than 10% of
the total flux and it is not required by the fit
XMM-Newton data
Campana et al. 2002
Heinke et al. 2007
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Simbol-X strenghts (for XRBs)
• Broad-band capabilities (0.5-80 keV)
• Large effective area at low and high energies
• Good timing capabilities
• Focusing instrument and thus low background
(e.g. wrt RXTE)
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Simbol-X: atoll spectrum
kTC
100 ks
Fx=10-9 erg/s/cm2
Lx=4x1036 erg/s @ 5 kpc
Monitoring of parameters
variations: study the physics
3σ
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Simbol-X: very hard tails
kTc=5 keV 40 ks
Tau=3
CONT: Fx=2x10-9 erg/s/cm2
TAIL: Fx=6x10-12 erg/s/cm2
Tail/Cont(0.5-20)= 0.1%
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NS transient in quiescence
100 ks
Diagnostic of the
power law tail and of
its variability
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SAX J1808.4-3658 in quiescence
100 ks
XMM
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Summary
Different mechanisms for explaining the transition to and the quiescent emission of NS XRTs approach the problem from the point of view of physics
Simbol-X is the first observatory able to disclose the high energy part of the spectrum at very high S/N and for persistent and transient sources, making possible a thorough study of the emission mechanisms through monitoring the variability