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
di Breracampana@merate.mi.astro
.itBologna, May 2007
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
X-ray binaries: variable
State transitions: SIGMA
Barret & Vedrenne 1994
Limiting luminosity for all LMXRBs (NS+BH) at 4x1036 erg/s
Maccarone 2003
Campana et al. 1998
Hard tails: INTEGRAL
Tarana et al. 2007
4U 1820-30
Paizis et al. 2006
BH XRB
NS XRB
Homan et al. 2007
State transitions: jets
Belloni 2007
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
From outburst to quiescence
FAST !
e-folding time changing from ~20 d to ~1 d at transition
BeppoSAX data
Campana et al. 1998
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
NS transients in quiescence: variability
Campana et al. 2003 Rutledge et al. 2001Campana &Stella 2004
Aql X-1
Transient X-ray pulsars
Campana et al. 2007
Wijnands 2005
SAX J1808.4-3658
mcr
ab
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
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)
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
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%
NS transient in quiescence
100 ks
Diagnostic of the
power law tail and of
its variability
SAX J1808.4-3658 in quiescence
100 ks
XMM
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
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