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Magnetars are magnetically powered, rotating neutron stars

Magnetars are magnetically powered, rotating neutron stars. 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,

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Magnetars are magnetically powered, rotating neutron stars

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  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 1033 to 1036 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 (5-11s) 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 Ordinary Star (8-10 Msun) Newborn Neutron star AGE: 0-10 s 0-10 million years above 10 million yrs RADIO PULSARS

  6. 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)

  7. How were SGRs discovered?

  8. ApJ 1987

  9. ApJ 1995 AIP Conference Proceedings 366, 1995

  10. ~180000lys

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

  12. Chandra observation of SGR 1627-41

  13. SGR burst time history

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

  15. Persistent Emission

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

  17. SGR Timing Properties . • SGR 1806–20: P = 7.48 s = 8.3 x 10–11 s s–1 B = 3.2 x 1019 (P )1/2 G B ~ 8 x 1014 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 . B~ 5.6 x 1014 G P

  18. Object B-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 4.5x105 Strongest man-made B 107 Radio Pulsars 1012-1013 Magnetars 1014-1015

  19. What is the magnetar energy source? LX = 1035 erg/s Ė rot = 1033 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

  20. SGR 1900+14 1996 May 98 Aug 98 Sep-Oct 98 1999 2000 Gogus et al. 2002

  21. BURSTS

  22. Typical SGR Bursts • Brief • Soft • L ~ 10-2 – 103 LEdd • E ~1036 – 1041erg Gogus et al. 1999

  23. Intermediate SGR Bursts E ~ 6 x 1042erg Two more events August 29, 1998 & April 28, 2001 had E ~ 1041–42erg Continuum of burst energies Kouveliotou et al 2001

  24. March 5, 1979 (Mazets et al. 1979) August 27, 1998 Rate (c/s) (Feroci et al. 1999) Time (s) Giant SGR Flares • Hard initial spike + spin modulated soft tail • L ~ 106 – 107 LEdd • E ~ 1044 – 1045erg

  25. SGR 1900+14 Woods et al. 2001

  26. SGR 1627-41 SGR 1900+14 Kouveliotou et al. 2003 Woods et al. 2001

  27. 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

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

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

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

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

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

  33. Palmer et al, 2005

  34. Palmer et al, 2005

  35. 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/cm2 s • Total (isotropic) energy release>1046 erg (Peak) • and 5x1043 erg (tail) Some comparisons: GRB prompt emission peak fluxes: 10-8-10-3 ergs/cm2 s X-ray afterglows of long bursts: ~10-11 – 10-13 ergs/cm2 s Previous giant flares: ~10-3 ergs/cm2 s Typical SGR bursts: 10-9 – 10-6 ergs/cm2 s

  36. 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.

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

  38. SGR 1900+14 Frail et al Nature 1998

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

  40. VLA J180839-202439 Gaensler et al Nature 2005

  41. At a distance of D = 15 d15, the 1.4 GHz flux of VLA J180839-202439, at first detection, implies an isotropic spectral luminosity of 5D2x1015 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)

  42. 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

  43. SGR 1900+14 Frail et al Nature 1998

  44. Gaensler et al Nature 2005

  45. 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]

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