Magnetars are

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Magnetars are magnetically powered, rotating
neutron stars
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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
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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 (5-11 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
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Radio pulsars
Magnetars
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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
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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)
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How were SGRs discovered?
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ApJ 1987
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ApJ 1995
AIP Conference Proceedings 366, 1995
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180000 lys
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N49 and the March 5th error box
0.09 arcminsq
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Chandra observation of SGR 1627-41
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SGR burst time history
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Outburst of AXP 1E 2259586 in 2002
0 5000
10000 15000
Time (sec)
Kaspi et al 2003
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Persistent Emission
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SGR 1806-20
AXP 1E 1048.1-5937
Woods et al 2001
Kaspi et al. 2001
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SGR Timing Properties

• SGR 180620
• P 7.48 s
• 8.3 x 1011 s s1
• B 3.2 x 1019 (P )1/2 G
• B 8 x 1014 G (Kouveliotou et al. 1998)
• SGR 190014
• P 5.16 s
• 6.1 x 1011 s s1
• (Hurley et al. 1999 Kouveliotou et al. 1999)

.
.
P
P
.
B 5.6 x 1014 G
P
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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
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What is the magnetar energy source?
LX 1035 erg/s
E rot 1033 erg/s
Accretion several arguments why it does not
work i) No companions detected ii) Bursts cannot
be explained iii) ISMextremely 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
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SGR 190014
1996
May 98
Sep-Oct 98
1999
2000
Aug 98
Gogus et al. 2002
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BURSTS
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Typical SGR Bursts

• Brief
• Soft
• L 10-2 103 LEdd
• E 1036 1041 erg

Gogus et al. 1999
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Intermediate SGR Bursts

• E 6 x 1042 erg
• Two more events
• August 29, 1998
• April 28, 2001 had
• E 104142 erg
• Continuum of
• burst energies

Kouveliotou et al 2001
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Giant SGR Flares

• Hard initial spike spin modulated soft tail

• L 106 107 LEdd
• E 1044 1045erg

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SGR 190014
Woods et al. 2001
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SGR 1627-41
SGR 190014
Kouveliotou et al. 2003
Woods et al. 2001
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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

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SOC Systems
Solar Flares
Earthquakes
(Aschwanden et al. 2000)
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SOC Systems Earthquakes
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Burst Duration-Fluence Correlation
SGR 1806-20
SGR 190014
Gogus et al. 2001
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SGR 1806-20 DECEMBER 27, 2004
GIANT FLARE (SWIFT)
Palmer et al, Nature, 2005
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SGR 1806-20 December 27, 2004 GIANT FLARE (RHESSI)
Hurley et al, Nature 2005
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Palmer et al, 2005
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Palmer et al, 2005
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X-ray Flare Properties

• Main Peak duration 0. 5 s
• Rise time 1.5 msec
• Tail Duration 380 s (50 cycles_at_ 7.56s)
• Peak Flux 5 ergs/cm2 s
• Total (isotropic) energy release1046 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
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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.
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Detection of an expanding Radio Nebula associated
with the December 27, 2004 Giant Flare
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SGR 190014
Frail et al Nature 1998
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VLA image (330 MHz) of the area around SGR 1806-20
Crystal Brogan, NRAO/UoHawaii
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VLA J180839-202439
Gaensler et al Nature 2005
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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 190014 !
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)
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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
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SGR 190014
Frail et al Nature 1998
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Gaensler et al Nature 2005
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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) p1-2a
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Gaensler et al, Nature 2005
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RADIO Flare Properties

• the radio emission was 500 times more luminous
  than the 190014 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)
• Emin 4x1043 ergs

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OPEN QUESTIONS
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?
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