1. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 1 Hard X-ray Tails in Magnetars A Case Study for Simbol-X Diego Götz CEA Saclay

2. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 2 Introduction Magnetars are neutron stars whose main energy source is neither rotation nor accretion, but the magnetic energy There are 12 members and 3 candidates Historically they are didvided in 2 classes: the Anomalous X-ray Pulsars (AXPs) and the Soft Gamma-Ray Repeaters (SGRs) The AXPs have been originally identified as a « class » due to their narrow period distribution and due to other X-ray properties No evidence for companion stars; 2 (or 3 ?) are in Supernova Remnants (very faint IR counterparts, no Doppler delays in pulses) Rotational period of a few seconds (5-12 s) Secular spin-down (0.05-4)x10 -11 s/s L x ˜ 10 34 - 10 36 erg s -1 >> Rotational Energy Loss Very soft X-ray spectrum (kT~0.5 keV)

3. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 3 Introduction PdP/dt (s)(10 -11 s/s) 4U 0142+618.70.2 1E 2259+58670.05 1E 1048-59376.42-3 1E 1841-04511.84 AX J1845-037- RXS 1708-40112 CXO J0110-7282 XTE J1810-1975.51.8 Tr. CXO J1647-4510.60.1 Tr. 1E 1048 3 bursts in 8 yrs 1E 2259:>80 bursts in few hours XTE J1810:4 bursts in 3 yrs 4U 0142 1 burst in 8 yrs (+4 last week!) CXO J16471 burst “SGR-like” short bursts seen from five AXPs

4. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 4 Introduction SGRs: Initially considered a peculiar class of Gamma-Ray Bursts short, “soft”, “repeating”, L peak >>> L Eddington Durations kT~30 keV Spectra

5. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 5 Introduction 4 confirmed SGRs 3 are in the Galactic plane  typical distance ~several kpc one is in the N49 supernova remnant in the Large Magellanic Cloud (d=55 kpc) Soft X-ray spectra and timing properties similar to AXPs 1806-201900+14 0526-66 1627-41 1801-23 ?

6. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 6 Introduction 3 Giant Flares from 3 SGRs 1979 March 5 - SGR 0526-66 1998 August 27 - SGR 1900+14 2004 December 27 – SGR 1806-20

7. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 7 INTEGRAL/IBIS Discovery of Hard Tails AXPsSGRs Kuiper et al. 2004 Mereghetti et al. 2005 den Hartog et al. 2005 Molkov et al. 2005 Kuiper et al. 2006 Götz et al. 2006 Clear evidence for non-thermal persistent emission. Energetically important contribution: L(>10 keV) ~10 36 erg/s Spectrum above 10 keV hardens for AXPs, while for SGRs it softens The AXPs tails are pulsated up to 100% No clear physical model has yet been devloped for the broad-band spectra of Magnetars. Persistent hard X-ray emission can be due to: Bremsstrahlung photons produced in a thin layer close to the neutron star (Thompson & Belobodorov 2005). Cutoff at ~100 keV. at 100 km altitude in the magnetosphere through multiple resonant cyclotron scattering (Thompson et al. 2002). Cutoff at ~1 MeV Götz et al. 2006

8. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 8 2003 2004 - 20-100 keV power law spectrum - both spectral hardness and intensity correlate with burst rate - source “activity level” increased in 2003-2004… … leading to the Dec 27 Giant Flare Mereghetti et al. 2005 SGR 1806-20: variability PERSISTENT BURSTS

9. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 9 Giant Flare (Mereghetti et al. 2005, Tiengo et al 2005, Rea et al. 2005)

10. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 10 PULSE PERIOD POWER LAW INDEX (2-10 keV) 2-10 keV FLUX XMM 20-40 keV FLUX INTEGRAL/IBIS INFRARED FLUX Israel et al. (2005)

11. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 11 Long term variability: SGR 1900+14 Esposito et al. 2006 using SAX and INTEGRAL/IBIS data 2003-2004 1997

12. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 12 Simbol-X Simulations: 1708 10 ks Working Hypothesis: « traditional » 2 components model Black Body + power law with the addition an « upward » break at 10 keV (from  ~2.8 to  ~1.5), to cope with INTEGRAL data. The break is clearly detectable already with a 10 ks. The single power law gives an unacceptable fit  2 r ~2

13. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 13 Simbol-X Simulations: 1806 100 ks Input Model: Faint Blackbody component (discovered by XMM with a 50 ks observation) + a power law with a « downward » less stong break (from 1.2 to 1.8) With 100 ks fitting a single power law yields a  2 r ~1.2, while adding a broken one gets  2 r ~1.03. No strong evidence for a break, black body component not required. (S-X is 4 to 5 times less sensitive than XMM @ 2 keV) Single power law fit

14. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 14 Simbol-X Simulations: 1806 1 Ms With a 1 Ms observation all spectral components are found: fitting the data with a single yields a  2 r ~3.3; adding a break one gets a  2 r ~1.6; finally adding the black body component one gets  2 r ~1.02. Single power law fit

15. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 15 Conclusions Simbol-X will largely contribute to further unveiling the spectral porperties of Magnetars –We will be able to monitor the spectral changes of the sources on the 10-100 ks time scale (Note that we used sharp breaks in our simulations!) –A deep observation (100ks - 1Ms) will allow us to do a detailed spectral modeling on a very broad (1-80 keV) energy range Disentagle the differences between AXPs and SGRs –Only simultaneous broad band observations will allow us to study and try to understand the nature of the long term variability of these sources (not feasible with the current instrumentation) –The excellent sensitivity due to imaging will allow to Detect for the first time pulsations from SGRs (2.5 sigma level with INTEGRAL) Do broad band phase resoved spectroscopy –Possibly detect proton (electron?)-cyclotron resonant scattering absorbtion lines in the hard X-ray range, currently not expected in the current Magnetar model, but…

16. CEA DSM Dapnia SAp Hystorical CAF S STUDies (Iwasawa et al. 1992) Absorption detected in 1990 (from GINGA data)around 10 keV. Never detected again. It lies close to the CCD high energy “edge” Ecyc around 6-15 keV (B 15 ~0.8-2 G) Such shape was observed only after the burst activity state

17. CEA DSM Dapnia SAp Diego Gotz - Hard X-ray tails in Magnetars 15/05/2007 17 Conclusions Simbol-X will largely contribute to further unveiling the spectral porperties of Magnetars –We will be able to monitor the spectral changes of the sources on the 10- 100 ks time scale (Note that we used sharp breaks in our simulations!) –A deep observation (100ks - 1Ms) will allow us to do a detailed spectral modeling on a very broad (1-80 keV) energy range Disentagle the differences between AXPs and SGRs –Only simultaneous broad band observations will allow us to study and try to understand the nature of the long term variability of these sources (not feasible with the current instrumentation) –The excellent sensitivity due to imaging will allow to Detect for the first time pulsations from SGRs (2.5 sigma level with INTEGRAL) Do broad band phase resoved spectroscopy –Possibly detect proton(electron)-cyclotron resonant scattering absorbtion lines in the hard X-ray range (not expected in the current Magnetar model) –Sutdy the otburst mechanisms of the transient AXPs by observing them in outburst and quiescence (2 orders of magnitude flux variations!) XTE 1810 and CXO 1647 could not be studied during their outburst with INTEGRAL, but only at energies below 10 keV. Nothing is known to date about these sources in the hard X-ray band

18. CEA DSM Dapnia SAp XTE J1810-197: the first TAXP A 5.5s transient X-ray pulsar was dicovered in 2003 soon noticed to be an AXP