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NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences01:17

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In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis. This...
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Related Experiment Video

Updated: Jun 8, 2026

Visualization of Low-Level Gamma Radiation Sources Using a Low-Cost, High-Sensitivity, Omnidirectional Compton Camera
06:28

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Published on: January 30, 2020

A low-magnetic-field soft gamma repeater.

N Rea1, P Esposito, R Turolla

  • 1Institut de Ciéncies de l'Espai, Consejo Superior de Investigaciones Científicas, Institut d'Estudis Espacials de Catalunya, Facultat de Ciéncies, Campus UAB, Torre C5-parell, 2a planta, 08193 Bellaterra (Barcelona), Spain. rea@ieec.uab.es

Science (New York, N.Y.)
|October 16, 2010
PubMed
Summary

Magnetars, or neutron stars powered by intense magnetic fields, may not require extremely high surface fields. This study found a soft gamma repeater with magnetar-like bursts but a low magnetic field, challenging existing theories.

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Area of Science:

  • Astrophysics
  • High-energy astrophysics
  • Neutron star physics

Background:

  • Soft gamma repeaters (SGRs) and anomalous X-ray pulsars are X-ray sources with sporadic bursts.
  • These sources are hypothesized to be magnetars, powered by extreme magnetic fields (10^14–10^15 gauss).

Purpose of the Study:

  • To investigate the magnetic field strength of a soft gamma repeater exhibiting magnetar-like activity.
  • To determine if extremely high magnetic fields are essential for magnetar-like behavior.

Main Methods:

  • X-ray observations of the soft gamma repeater SGR 0418+5729.
  • Analysis of burst emissions to infer magnetic field properties.

Main Results:

  • SGR 0418+5729 exhibits magnetar-like bursts.
  • X-ray observations indicate a dipolar magnetic field below 7.5 × 10^12 gauss, typical of radio pulsars.
  • This suggests magnetar-like activity can occur with lower magnetic fields than previously assumed.

Conclusions:

  • A high surface dipolar magnetic field is not a prerequisite for magnetar-like activity.
  • The magnetar population may encompass a broader spectrum of magnetic field strengths, ages, and evolutionary states.
  • This finding broadens our understanding of neutron star diversity and magnetar formation.