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The greatest flare of a Soft Gamma Repeater

  • On December 27 2004 the greatest flare from SGR 1806-20 was detected by many satellites: Swift, RHESSI, Konus-Wind, Coronas-F, Integral, HEND, …

  • 100 times brighter than ever!


Подборку оригинальных статей можно найти здесь: http://xray.sai.msu.ru/~polar/sci_rev/05_02_15-28.html



Magnetars in the Galaxy

  • 4 SGRs, 8 AXPs, plus candidates, plus radio pulsars with high magnetic fields …

  • Young objects (about 104 yrs).

  • Probably about 10% of all NSs.



Alternative theory

  • Fossil disk

  • Mereghetti, Stella 1995

  • Van Paradijs et al.1995

  • Alpar 2001

  • Marsden et al. 2001

  • Problems …..

  • How to generate strong bursts?



Why “magnetars”?

  • dE/dt > dErot/dt

  • By definition: magnetically-powered NSs

  • P-Pdot

  • Direct field measurements (Ibrahim et al.)



Known magnetars

  • SGRs

  • 0526-66

  • 1627-41

  • 1806-20

  • 1900+14

  • +candidates



Magnetic field measurements

  • Direct measurement of the magnetic field of the SGR

  • Spin-down

  • Long periods



Are SGRs and AXPs relatives?

  • SGR-like bursts from AXPs

  • Spectral properties

  • Quiet periods of SGRs (0525-66 since 1983)



Historical notes

  • 05 March 1979. Cone experiment. Venera-11,12 (Mazets et al.)

  • Event in LMC. SGR 0520-66.

  • Fluence: about 10-3 erg/cm2



Main types of activity of SGRs

  • Weak burst. L<1041 erg/s

  • Intermed. bursts.L=1041–1043 erg/s

  • Giant bursts. L<1045 erg/s

  • Hyperflares. L>1046 erg/s



Common (weak) bursts from SGRS and AXPs

  • Typical burst from SGR 1806-29, SGR 1900+14 and from AXP 1E 2259+586 observed by RXTE (from Woods, Thompson, 2004, astro-ph/0406133)



Intermediate SGR bursts

  • Four intermediate bursts. However, the forth is sometimes considered as a giant one (from Woods, Thompson)



Giant flare from SGR 1900+14 (27 Aug 1998)

  • Data from Ulysses (figure from Hurley et al. 1999a)

  • Spike 0.35 sec

  • P=5.16 sec

  • L>3 1044 erg/s

  • ETOTAL>1044 erg

  • Influenced the Earth ionosphere



27 Dec 2004 giant outburst of SGR 1806-20

  • Spike 0.2 sec

  • Fluence 1 erg/cm2

  • E(spike)3.5 1046 erg

  • L(spike)1.8 1047 erg/s

  • Long tail (400 s)

  • P=7.65 s

  • E(tail) 1.6 1044 erg

  • Distance 15 kpc



Konus-Wind data om SGR 1806-20 27 Dec 2004 flare



SGR giant flares vs. GRBs



SGRs and starformation

  • Possibility of a SGR detection outside the Local group of galaxies

  • Starforming galaxies are the best sites for a search

  • <5 Mpc. M82, M83, NGC 253

  • About 40 Mpc. Arp 299, NGC 3256

  • Possible candidates in the BATSE catalogue of short GRBs



Theory of magnetars

  • Thompson, Duncan ApJ 408, 194 (1993)

  • Entropy-driven convection in young NSs generate strong magnetic field

  • Twist of magnetic field lines



Magnetars origin (a speculative discussion)

  • Fast rotation is necessary (Thompson, Duncan)

  • Spin-up of a progenitor star in a binary via accretion or synchronization

  • Coalescence

  • About 10% of NSs (Popov, Prokhorov 2005)