1. Magnetars are magnetically powered, rotating neutron stars

2. RADIO PULSARS 2000 discovered to date Radiate covering most of the electromagnetic spectrum Rotate with periods that span five decades (ms to a few hours). Are powered by their own rotational energy, residual surface heat or accretion Live tens of millions of years

3. MAGNETARS (11 discovered to date) Radiate almost entirely in X-rays, with luminosities ranging between 10 33 to 10 36 erg/s Emit typically brief (1-100 ms) bursts that may exceed Eddington Luminosities and very rarely, Giant Flares Rotate in a very narrow period interval (5-11 s) and slow down faster than any other object (~10 -10 -10 -11 s/s) Are powered by magnetic field energy, which heats the neutron star interior so that the surface glows persistently in X-rays, and fractures the crust inducing short, repeated bursts at random intervals. Die rather young; typical ages are ~10000 yrs

4. Radio pulsars Magnetars

5. MAGNETARS AGE: 0-10 s 0-10,000 years above 10,000 years AGE: 0-10 s 0-10 million years above 10 million yrs RADIO PULSARS Ordinary Star (8-10 Msun) Newborn Neutron star

7. Several neutron star populations may belong to the Magnetar class: Soft Gamma Repeaters (SGRs) Anomalous X-ray Pulsars (AXPs) Dim Isolated Neutron Stars (DINs) Compact Central X-ray Objects (CCOs)

8. How were SGRs discovered?

9. ApJ 1987

10. ApJ 1995 AIP Conference Proceedings 366, 1995

12. ~180000 lys

13. N49 and the March 5 th error box 0.09 arcminsq

14. Chandra observation of SGR 1627-41

16. SGR burst time history

17. 0 5000 10000 15000 Time (sec) Outburst of AXP 1E 2259+586 in 2002 Kaspi et al 2003

18. Persistent Emission

19. Woods et al 2001 SGR 1806-20 Kaspi et al. 2001 AXP 1E 1048.1-5937

20. SGR Timing Properties SGR 1806–20: P = 7.48 s = 8.3 x 10 –11 s s –1 B = 3.2 x 10 19 (P ) 1/2 G B ~ 8 x 10 14 G (Kouveliotou et al. 1998) SGR 1900+14: P = 5.16 s = 6.1 x 10 –11 s s –1 (Hurley et al. 1999; Kouveliotou et al. 1999). P. P. P B ~ 5.6 x 10 14 G

21. ObjectB-field (Gauss) Galactic nuclei 10 -2 -10 -3 Our Galaxy 2x10 -6 Planets: Jupiter 4 Earth 0.6 Sun (general field) 1 (sunspots) 4,000 Common iron magnet 100 Common MRI field 10,000 Strongest SUSTAINED Lab fields 4.5x10 5 Strongest man-made B 10 7 Radio Pulsars 10 12 -10 13 Magnetars 10 14 -10 15

22. What is the magnetar energy source? L X = 10 35 erg/s Ė rot = 10 33 erg/s Accretion: several arguments why it does not work i) No companions detected ii) Bursts cannot be explained iii) ISM:extremely dense and cold medium + extremely slow SGR iv) fossil disc: detection of persistent emission immediately after giant flare argues against it Magnetar model (Duncan and Thompson 92) Decay of a super-strong magnetic field

24. SGR 1900+14 1996May 98Sep-Oct 9819992000Aug 98 Gogus et al. 2002

25. BURSTS

26. Typical SGR Bursts Brief Soft L ~ 10 -2 – 10 3 L Edd E ~ 10 36 – 10 41 erg Gogus et al. 1999

27. Intermediate SGR Bursts E ~ 6 x 10 42 erg Two more events August 29, 1998 & April 28, 2001 had E ~ 10 41–42 erg Continuum of burst energies Kouveliotou et al 2001

28. Giant SGR Flares (Mazets et al. 1979) March 5, 1979 (Feroci et al. 1999) Time (s) Rate (c/s) August 27, 1998 L ~ 10 6 – 10 7 L Edd E ~ 10 44 – 10 45 erg Hard initial spike + spin modulated soft tail

30. SGR 1900+14 Woods et al. 2001

31. Kouveliotou et al. 2003 SGR 1900+14 SGR 1627-41

32. Self-Organized Criticality It states that composite systems self-organize to a CRITICAL STATE where a slight perturbation can cause a chain reaction of any size. SOC is the evolution of a system into an organized form in the absence of any external constraints. Systems evolve from non- or slight correlation to a high degree of correlation (critical state) Simple models: Sand piles, Earthquakes, stock market

33. SOC Systems (Aschwanden et al. 2000) (Lay & Wallace 1995) Earthquakes Solar Flares Earthquakes Solar Flares

34. SOC Systems: Earthquakes (adopted from Nadeau & McEvilly 1999) Recurrence Times of Micro Earthquakes Duration – Magnitude Correlation of Earthquakes (adopted from Lay & Wallace 1995)

35. Burst Duration-Fluence Correlation SGR 1806-20SGR 1900+14 Gogus et al. 2001

36. SGR 1806-20 DECEMBER 27, 2004 GIANT FLARE (SWIFT) Palmer et al, Nature, 2005

37. SGR 1806-20 December 27, 2004 GIANT FLARE (RHESSI) Hurley et al, Nature 2005

38. Palmer et al, 2005

40. X-ray Flare Properties Main Peak duration ~ 0. 5 s Rise time ~ 1.5 msec Tail Duration ~ 380 s (50 cycles@ 7.56s) Peak Flux >5 ergs/cm 2 s Total (isotropic) energy release>10 46 erg (Peak) and 5x10 43 erg (tail) Some comparisons: GRB prompt emission peak fluxes: 10 -8 -10 -3 ergs/cm 2 s X-ray afterglows of long bursts: ~10 -11 – 10 -13 ergs/cm 2 s Previous giant flares: ~10 -3 ergs/cm 2 s Typical SGR bursts: 10 -9 – 10 -6 ergs/cm 2 s

41. Giant Flares and short GRBs The two previous giant flares could have been detected Up to 8 Mpc; the recent one up to 40 Mpc Taking into account the SFR in our Galaxy, we would expect 80 such events per year to be compared with the 150 BATSE detected The isotropic distribution of short GRBs, the lack of excess from Virgo cluster indicates that at most 5% of short GRBs are SGR GFs or The distance to SGR 1806-20 is less than 15 kpc The SGR GF rate is less than assumed, the GF rate is less than 1/30-40 years, or there are more luminous GFs.

42. Detection of an expanding Radio Nebula associated with the December 27, 2004 Giant Flare

43. Frail et al Nature 1998 SGR 1900+14

44. Crystal Brogan, NRAO/UoHawaii VLA image (330 MHz) of the area around SGR 1806-20

45. Gaensler et al Nature 2005 VLA J180839-202439

46. At a distance of D = 15 d 15, the 1.4 GHz flux of VLA J180839-202439, at first detection, implies an isotropic spectral luminosity of 5D 2 x10 15 W/Hz, which is ~ 700 times larger than the radio afterglow seen from SGR 1900+14 ! International campaign monitoring over 0.35-16 GHz the AG from days 6-19 after the GF: VLA, ATCA, WSRT, MOST here (MERLIN, VLBA, GBT pending)

47. The nebula shape is resolved at 8.5 GHz: except for day 16.8, the source is elliptical with axial ratio ~0.6 and major axis oriented ~60º W to N Constant isotropic expansion at 0.27(10)c until day 19.7

48. SGR 1900+14 Frail et al Nature 1998

49. Gaensler et al Nature 2005

50. The light curve exhibits an achromatic break at 8.8 days: e.g. at 4.8 GHz the decay index transitioning from 1.5 to 2.84 Significant linear polarization indicating synchrotron radiation. The early PA indicated B field alignment with the nebular axis Spectral steepening at high freg. From day 11.2 single PL (0.84-8.5 GHz) with index -0.75(2)-> electron index p= 2.50(4) [p=1-2a]

51. Gaensler et al, Nature 2005

52. RADIO Flare Properties the radio emission was 500 times more luminous than the 1900+14 flare (at 15 kpc) the radio emission lasted over 45 days and counting the light curve exhibits a VERY STEEP achromatic break the spectrum is consistent with a power law index of –0.75(2) from 0.84 – 8.5 GHz VARIABLE linear polarization the radio nebula expands with 0.3c (~ 4mas per day) E min > 4x10 43 ergs

53. What is the association between bursts and spin changes? Is there a thermal component in the persistent emission in all magnetars? When does it emerge? Are there lines in the X-ray spectra of magnetars? Is there an association of magnetars with Supernovae Remnants and clusters of very massive stars? Which are the magnetar progenitors? What is the magnetar formation Rate? OPEN QUESTIONS