Rotating magnetized neutron stars

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Rotating magnetized neutron stars

• for SGR 0525-66 (5/3/79)
• 1 ms 8 s in 10 kys
• .
• P 3 x 10-11 s s-1
• B 1015 G !!
• ?
• MAGNETAR

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Rotating magnetized neutron stars
Very high fields ? Fast spindown ? SGRs are
young NSs which should still be associated to SNRs
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MAGNETARS
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MAGNETARS

• How do the bursts happen?
• NS crust brakes due to EM tensions (starquakes)
• Alfvén waves injected in the magnetosphere
• particle acceleration
• optically thick pair plasma forms
• gamma-ray emission

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MAGNETARS
Problems In 190014,
RXTE measured a much . smaller P 2
ys before the 1998 active period ?? EB increased
by more than 100 ? Spindown is not magnetic and
may be due to relativistic winds (no magnetar!)
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BeppoSAX and Afterglows

• BeppoSAX
• - 4 narrow field instruments
• (.1 to 300 keV arcminute res.)
• - Wide Field Camera
• (2 to 25 keV 200 x 200 5 coded-mask)
• - Gamma Ray Burst Monitor
• (60 to 600 keV side shield)

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BeppoSAX and Afterglows

• 97 Feb 28 GRB 970228
• Discovered by GRBM and WFC
• NFIs observe 1SAX J0501.71146
• ?
• First clear evidence of a GRB X-ray tail
• ? Non-thermal spectra
• ? X-ray fluence is 40 of ?-ray fluence

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BeppoSAX and Afterglows

• BeppoSAX and RXTE discovered several other
  afterglows
• Optical transients
• Observed in appr. ½ of the well localized bursts
• GRB 990123 is the only one observed in the
  optical when the gamma-ray flash was still going
  on

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GRB 990123
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GRB 011121
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GRB 011121
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Host galaxies

• Optical IDs ? distant galaxies
• (low luminosity, blue)
• 20 measured redshifts
• All in the z 0.3 4.5 range, with the
  exception of GRB 980425, possibly associated with
  SN 1998bw _at_ z 0.008
• OT is never far from center

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redshifts
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Progenitors

• Long GRBs are probably associated with massive
  and short-lived progenitors
• ?
• GRBs may be associated with rare types of
  supernovae
• Hypernovae colapse of rotating massive star ?
  black hole accreting from a toroid
• Collapsar coalescence with a compact companion ?
  GRBs and SN-type remnant

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Progenitors

• Short GRBs are probably associated with mergers
  of compact objects

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The fireball model

• Observed fluxes require 1054 erg emitted in
  seconds in a small region (km)
• ?
• Relativistic expanding fireball (e , ?)
• Problem energy would be converted into Ek of
  accelerated baryons, spectrum would be
  quasi-thermal, and events wouldnt be much longer
  than ms.
• Solution fireball shock model shock waves will
  inevitably occur in the outflow (after fireball
  becomes transparent) ? reconvert Ek into
  nonthermal particle and radiation energy.

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The fireball model

• Complex light curves are due to internal shocks
  caused by velocity variations.
• Turbulent magnetic fields built up behind the
  shocks ? synchrotron power-law radiation spectrum
  ? Compton scattering to GeV range.
• Jetted fireball fireball can be significantly
  collimated if progenitor is a massive star with
  rapid rotation ? escape route along the rotation
  axis ? jet formation ? alleviate energy
  requirements ? higher burst rates

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High Energy Transient Explorer

• First dedicated GRB mission, X- and g-rays
• Equatorial orbit, antisolar pointing
• launched on Oct 9th, 2000 - Pegasus
• 3 instruments, 1.5 sr common FOV
• SXC (0.5-10 keV) - lt 30 localization
• WXM (2 25 keV) - lt 10 localization
• FREGATE (6-400keV) - ? sr localization
• Rapid dissemination (? 1s) of GRB positions
• (Internet and GCN)

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HETE
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HETE Investigator Team
RIKEN Masaru Matsuoka Nobuyuki Kawai Atsumasa
Yoshida
UC Berkeley Kevin Hurley J. Garrett Jernigan
MIT George R. Ricker (PI) Geoffrey Crew John
P.Doty Al Levine Roland Vanderspek Joel
Villasenor
UChicago Donald Q. LambCarlo Graziani
CESR Jean-Luc Atteia Gilbert Vedrenne
Jean-Francois Olive Michel Boer
INPE João Braga
LANL Edward E. Fenimore Mark Galassi
CNR Graziella Pizzichini
CNES Jean-Luc Issler
UC Santa Cruz Stanford Woosley
SUPAERO Christian Colongo
TIRF Ravi Manchanda
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HETE in the Pegasus
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Ground station network
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GRB 010921

• Bright (gt80?) burst detected on Sept 21, 2001
  051550.56 UT by FREGATE
• First HETE-discovered GRB with counterpart
• Detected by WXM, giving good X position
• (10o x 20 strip)
• Cross-correlation with Ulysses time history
• ?
• IPN annulus (radius 60o 0.118o)
• intersection gives error region with 310 arcmin2
  centered at
• ? 22h55m30s, ? 40052

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GRB 010921
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GRB 010921

• Highly symmetric at high energies
• Lower S/N for WXM due to offset
• Durations increase by 65 at lower energies
• Hard-to-soft spectral evolution
• Peak energy flux in the 4-25 keV band is 1/3 of
  50-300 keV
• Peak photon flux is 4 times higher in the 4-25
  keV

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Discussion

• Long duration GRB
• X-ray rich, but no XRF (high 50-300 keV flux)
• z 0.450 ? isotropic energy of 7.8 x 1051 erg
  (?M0.3, ??0.7, H065 km s-1 Mpc-1) - less
  if beamed
• Second lowest z ? strong candidate for extended
  searches for possible associated supernova
• Final position available 15.2h after burst ?
  ground-based observations in the first night ?
  counterpart established well within HETE-IPN
  error region

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Conclusions

• GRBs occur at a rate of (no beaming)
• a few/day/universe
• or 1/few million ys/average galaxy
• or 10-91 cm-3 s-1
• (since observed GRBs are detectable out to z 10)
• New missions are very important
• SWIFT 3 instruments, 250-300 bursts/yr, coverage
  from optical to gamma-rays, arcsecond positions,
• will detect bursts up to z 20.
• INTEGRAL, EXIST, MIRAX
• Cosmology burts can proble early universe and
  some could be related to Pop III stars ??
• metal enrichment and ionization of the
  primordial gas.