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Fenomeni Transienti nei Magnetars (i piu' potenti magneti dell'universo) Gian. Luca Israel (osservatorio astronomico Fenomeni Transienti nei Magnetars (i piu' potenti magneti dell'universo) Gian. Luca Israel (osservatorio astronomico di Roma/monteporzio) INAF (Roma/Milan/Palermo): P. Romano, V. Mangano, F. Bernardini, M. Burgay, A. Possenti, P. Esposito, D. Gotz, S. Mereghetti, G. Chincarini, L. Stella, S. Campana, T. Belloni, G. Tagliaferri, A. Moretti, C. Guidorzi, A. Albano (also Univ. Padova) Univ. Pisa: S. Dall’ Osso (also INAF Roma) MSSL (London): S. Zane, J. Blustin, R. Mignani NASA/GSFC: T. Sakamoto, N. Gehrels, H. Krimm PSU: D. Burrows LANL: D. Palmer Berkeley: K. Hurley JILA: R. Perna Caltech: M. Muno GSFC: J. Cummings 08 May 7 SAIt 08

Studying Magnetars Identifying their nature. Observational properties did not fit into any of the Studying Magnetars Identifying their nature. Observational properties did not fit into any of the known class of astrophysical objects. Understanding their emission mechanism(s). Theoretical models involve peculiar objects. If correct, AXPs/SGRs would be the first class of astrophysical objects the emission of which is mainly driven by decay of high magnetic fields (>10^15 Gauss !!). AXPs/SGRs are rare objects (<15) which might allow us to test the physics under extreme conditions (grav. field, B, density/pressure, etc. ) 08 May 7 SAIt 08

OUTLINE Transient phenomena in AXPs/SGRs QPOs in GF SGR 1806 -20 Timescales of Frac. OUTLINE Transient phenomena in AXPs/SGRs QPOs in GF SGR 1806 -20 Timescales of Frac. /few ms discovery of QPOs (L. Stella’ s talk) Bursts: Type A and B Timescales of 10 -100 ms 4 U 0142+614, 1 E 1048. 1 -5937, 2 E 2259+586: Persistent AXPs CXOUJ 164710. 2 -455216, XTEJ 1810 -197: Transient APXs Intermediate flares: Timescales of 1 -40 s SGR 1900+14 sampling of the trapped fireball Outbursts Timescales of months/years XTE J 1810 -197 the outburst fading [1 -4 yr] CXOU J 164710. 2 -455216 the outburst onset [0 -1. 5 yr] 08 May 7 SAIt 08

Why transient and outbursts ? In analogy with studies done in the past on Why transient and outbursts ? In analogy with studies done in the past on transient X-ray pulsars in binary systems the (identification and) study of transient AXPs might give insights on : • the emission mechanisms (mainly unknown) as a function of flux (continuously changing main parameters) for a constant distance, geometry and magnetic field B. Outburst timescales (years) are such that monitoring observations are easy to set. 08 May 7 SAIt 08

From Quiescence to outburst On 2006 September 21 st BAT recorded a 20 ms From Quiescence to outburst On 2006 September 21 st BAT recorded a 20 ms long and intense (for an AXP… Lx~1039 erg/s) burst from CXOU J 164710 -455216 (after 2 E 2259+58, 1 E 1048 -59 and 4 U 0142+61) (Note that in 3 years and ~300 events Swift BAT no GRB – or false event - was ever (15 -150 ke. V) detected within 3’ from the position of any AXPs/SGRs). Pre or post outburst ? ? No XRT pointing due to the presence of a bright X-ray source GX 340 -2 at 20’. Moreover the burst was tagged as not real…… k. T~10 ke. V or G=1. 8 First pointing was finally carried out after 13 hours ! (Israel et al. 2007) 08 May 7 SAIt 08

The Awakening of the AXP in Westerlund 1 The source was detected at a The Awakening of the AXP in Westerlund 1 The source was detected at a Lx level of 1036 ergs/s ~300 -400 times larger than the week before !! The largest flux enhancement ever detected for an AXP. The spectrum was different form the quiescent level one We started an X-ray (Swift/XMM) and Radio (Parkes) To. O monitor campaign PL~3. 5 (60%of total) BB~0. 5 ke. V R~ 0. 4 km PL~2. 2 (60%of total) BB~0. 65 ke. V R ~ 2 km 08 May 7 SAIt 08

PHASE-coherent timing: PULSE shapes S Time XMM-Newton H © ® © Swift XMM-Newton chandra PHASE-coherent timing: PULSE shapes S Time XMM-Newton H © ® © Swift XMM-Newton chandra Peak identification based on the assumption of maximizing the constant parameters: 2 peaks almost constant ( © ) 1 peak highly variable ( ® ) After 6 months the pulse shape is still very different from that in quiescence Pulse variability testifies to changes in the emission pattern, From rather simple (sinusoid) to complex and energy dependent 08 May 7 SAIt 08

PHASE-coherent timing: a glitching AXP Our Pdot of 9. 2(4)x 10 -13 s/s implies PHASE-coherent timing: a glitching AXP Our Pdot of 9. 2(4)x 10 -13 s/s implies a dipole field strength of ~ 1014 G. (Israel et al. 2006, 2007) A glitch (Dn/n ~ 6. 5 x 10 -5) occurred within 0. 8 days from the burst epoch (the largest ever detected in a NS). We also revealed the presence of the secular spin-down trend. (Woods et al. 2003) 2 E 2259+58 Dn/n ~ 4 x 10 -6 Energy: the glitch par. imply an energy release of 5 x 1041 ergs (three months) 0. 004% emitted in the burst 6% stored in the NS and released in 2 days 90% went to increase the persistent flux 08 May 7 SAIt 08

From outburst to quiescence: XTe. J 1810 -197 A 5. 5 s transient X-ray From outburst to quiescence: XTe. J 1810 -197 A 5. 5 s transient X-ray pulsar was dicovered in 2003 Israel et al. 2006 Timing and spectral properties consistent with those of AXPs NH = 1. 05(5) x 1022 cm-2 k. T = 0. 67 +/- 0. 01 ke. V P=5. 5 s Pdot=2 10 -11 s/s 14 G = 3. 7 +/- 0. 2 (k. T=0. 3 ke. V) B = 2. 4 x 10 G PF=46(3)% 08 May 7 SAIt 08

The spectral evolution XMM (2003) 2 BBs used to account for the + XMM The spectral evolution XMM (2003) 2 BBs used to account for the + XMM (2004) X-ray emission from the NS Surface (Gotthelf & Halpern 2006). k. T 1= 0. 25(1) ke. V k. T 2= 0. 67(1) ke. V + ROSAT Fx ~ 5 x 10 -13 erg s-1 cm-2 BB with k. T=0. 18(2) ke. V and R~10 km No pulsations with PF>20 -25% Lx~1033 erg/s @ 4 kpc not distinguishable from hundreds of unidentified ROSAT sources Open Issues: • Does the XMM Soft BB evolve into the ROSAT BB component ? • Is the quiescent ROSAT BB component always there (and constant) ? • Which is (will be) the XMM Hard BB component evolution ? • Is there any other component present/appearing/disappearing through the outburst ? • Which is the PF at quiescence ? Is the modified BB really needed ? Federico Bernardini thesis 08 May 7 SAIt 08

the SPECTRAL evolution – 3 BBs Mar 06 9 DDT/GO obs (DFx~50 ) H the SPECTRAL evolution – 3 BBs Mar 06 9 DDT/GO obs (DFx~50 ) H H S S sep 06 Hard BB disappeared between MAR and SEP 06 -> PF flattens (Bernardini et al. 2008) 2 BB -> 3 BB Ftest gives p~10 -12 Tail component present between 03 -04 possibly related to a HE PL observed in other AXPs (3 s c. l. ) 08 May 7 SAIt 08

XMM/Parkes: NO correlated variability ! No significant X-ray variability during the radio transitions. Flux~const XMM/Parkes: NO correlated variability ! No significant X-ray variability during the radio transitions. Flux~const however Fr~0. 01 Fx Bright Fading Dim Mar 07 Fading Sep 06 X-ray peak phase : 0. 151+-0. 005 Radio peak phase : 0. 151+-0. 019 No significant variations in the X/radio shift between Sep 06 and Mar 07. X-ray/radio alignment X-rays and radio are coming from the same portion of the NS. A larger X-ray duty cycle indicates a larger emitting area for X-rays. PPS analysis confirms that 2 BB emitting regions are in phase Radio variability not easily correlated to X-rays - no significant flux variations In agreement with the idea that most of the X-rays originated deep in the crust after thermalization. 08 May 7 SAIt 08

Conclusions - I TAXP studies seems to be a very powerful tool to study Conclusions - I TAXP studies seems to be a very powerful tool to study the emission mechanism(s) from AXPs and their evolution. The exceptional case of XTEJ 1810 -197 and its radio emission is even more important allowing to identify a common emission region for X-rays and radio Open questions to be addressed in the near future: - Are the outbursts permanently modifying the timing/spectral parameters of the source ? - Are different outbursts behaving similarly ? More than one type of outbursts ? Application of more physical spectral models The Swift detection of a burst from an AXPs increased the chances to identify other outburst form known AXPs and to select new AXPs. 08 May 7 SAIt 08

The 2006 burst Forest SGR 1900+14 as observed by Swift on 29 th March The 2006 burst Forest SGR 1900+14 as observed by Swift on 29 th March 2006 More than 100 single bursts were detected in 20 min, with 40 in less than 30 s. Few of them have intermediate duration (200 ms-2 s). Total Energy: few x 1042 ergs (one of the more energetic events recorded ever after the 1998 giant flare) Time resolved spectroscopy Resulted in 729 spectra with an average # of photons of 4000 and Dt in the 8 -400 m range 08 May 7 SAIt 08

2 BB: time-resolved evolution <k. Ts>=4. 8+-0. 3 ke. V <Rs>=30+-2 km Possibly related 2 BB: time-resolved evolution =4. 8+-0. 3 ke. V =30+-2 km Possibly related to the Magnetosphere =9+-0. 3 ke. V =5. 7+-0. 5 km Possibly related to the NS surface k. Ts/k. Th ~ 0. 5 Rs/Rh ~ 6 Given the statistics and the time resolution it rather interesting to look at the T and R distributions (Olive et al. 2004 on a 4 s-long IF) 08 May 7 SAIt 08

The KT - R 2 plane Sharp edge / saturation present for the brightest The KT - R 2 plane Sharp edge / saturation present for the brightest part of the bursts The 2 BB distributions identify a natural separation surface at 20 -25 km k. T-3 k. T-4 ◊ Olive 2004 10 -13 ke. V A sort of turn/cut-off is present for the BBh around 10 -13 ke. V and 5 -15 km The locus identified by the relation R 2 k. T 3=c can be regarded as constant number of emitted g per unit time (R 2 k. T 4=c identifies a constant L) 08 May 7 SAIt 08

2 BB: Lsoft vs Lhard BBs and BBh Luminosities correlate below 3 x 1041 2 BB: Lsoft vs Lhard BBs and BBh Luminosities correlate below 3 x 1041 erg/s. Above such value only BBh increases. BBs saturation effect t Max LBBh is ~3 x 1041 erg/s at 10 ke. V and 15 km = magnetic Eddington luminosity (Paczynsky 1992) for B of 8 e 14 G [similar to that inferred form P and Pdot]. LEdd, B(r) ≈ 2 LEdd (B(r)/1012)4/3 Max LBBs ~ 1041 erg/s at 100 km hints to the maximum efficiency of the MF to substain the radiation pressure. 08 May 7 SAIt 08

THE proposed/qualitative scenario A possible interpretation: different way with which Eand O-mode polarised photons THE proposed/qualitative scenario A possible interpretation: different way with which Eand O-mode polarised photons propagate into the magnetosphere (TD 95); scattering cross section of Emode is reduced by B and the scattering photosphere is smaller (~R NS). O-mode g photosphere The R=30 km corresponding to the max radius of the BBh and the min of the BBs identify a critical surface at which B=Bcrit (QED). E-O-mode g splitting photosphere E-mode g photosphere O-e--e+ E O O B

Conclusions - I TAXP studies seems to be a very powerful tool to study Conclusions - I TAXP studies seems to be a very powerful tool to study the emission mechanism(s) from AXPs and their evolution. The exceptional case of XTEJ 1810 -197 and its radio emission is even more important allowing to identify a common emission region for X-rays and radio Open questions to be addressed in the near future: - Are the outbursts permanently modifying the timing/spectral parameters of the source ? - Are different outbursts behaving similarly ? More than one type of outbursts ? Application of more physical spectral models The Swift detection of a burst from an AXPs increased the chances to identify other outburst form known AXPs and to select new AXPs. 08 May 7 SAIt 08

Conclusions - II We carried out a detailed spectroscopic study of the bursting component Conclusions - II We carried out a detailed spectroscopic study of the bursting component of SGR 1900+14 thanks to a “dream dataset“ collected by Swift on March 2006 (Israel et al. 2008). We tested the magnetar model scenario [detail level not sufficient!]. • a 2 BB spectral distribution is confirmed to be the best multi-comp. model • Discovery of a correlation between T and BB surface S (Sk. T 3=const) which holds for the brightest (or initial) part of the bursts. It gives info on the different emission mechanisms involved (Compton versus photon splitting) • a break of the Ls/Lh=const relation, above 1041 erg/s saturation effect in the soft component. Interpreted in the framework of the magnetar model as the existence of E- and O-mode g populations • The maximum L of the hard BB (@ 15 km and 10 ke. V) is similar to the inferred LEdd, B at the same radius for B~8 x 1014 G (inferred form P and Pdot). Moreover, the super- shown by the soft BB at large distance (100 km) testifies of the presence of a dynamically active magnetic confinement • short burst and IF do not behave differently each other. They form a continuous in terms od duration and fluence 08 May 7 SAIt 08