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Statistical Properties of SGR 1900+14 Bursts.
The Astrophysical Journal
|November 7, 1999
Summary
Soft gamma repeater (SGR) bursts exhibit scale-free energy distributions, similar to earthquakes, suggesting self-organized criticality. Their burst statistics indicate an internal magnetic energy source within neutron stars.
Area of Science:
- Astrophysics
- High-energy astrophysics
- Neutron star physics
Background:
- Soft gamma repeaters (SGRs) are neutron stars emitting powerful bursts of gamma rays.
- Understanding the underlying physics of SGR bursts is crucial for neutron star evolution and high-energy phenomena.
Purpose of the Study:
- To statistically analyze the properties of soft gamma repeater bursts from SGR 1900+14.
- To investigate the energy source and underlying mechanisms of SGR bursts by comparing their statistical properties to other astrophysical phenomena.
Main Methods:
- Analyzed a database of 187 bursts from BATSE and 837 bursts from the Rossi X-Ray Timing Explorer Proportional Counter Array for SGR 1900+14.
- Examined the fluence/energy distribution, time interval distribution, and correlations between burst properties (intensity, duration, waiting times).
Main Results:
- Burst fluence distribution follows a power law (index 1.66) over four orders of magnitude, indicating scale-free behavior.
- Time intervals between bursts are lognormally distributed.
- No correlation found between burst intensity and subsequent waiting times, but a correlation exists with preceding time intervals.
- Burst duration and energy are correlated, albeit with significant scatter.
Conclusions:
- SGR burst statistics resemble those of earthquakes and solar flares, not accretion or nuclear-powered phenomena.
- The findings support the hypothesis that SGR bursts are powered by internal magnetic energy stored within the neutron star.
- Evidence suggests self-organized criticality as a potential mechanism governing SGR activity.