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Published January 1, 2011 | Version v1
Journal article Open

Fermi/GAMMA-RAY BURST MONITOR OBSERVATIONS OF SGR J0501+4516 BURSTS

Creators

  • 1. NASA, Space Sci Off, Marshall Space Flight Ctr, Huntsville, AL 35812 USA
  • 2. Rice Univ, Dept Phys & Astron, Houston, TX 77251 USA
  • 3. Univ Space Res Assoc, NSSTC, Huntsville, AL 35805 USA
  • 4. Univ Alabama, CSPAR, Huntsville, AL 35805 USA
  • 5. Corvid Technol, Huntsville, AL 35806 USA
  • 6. Sabanci Univ, Fac Engn & Nat Sci, TR-34956 Istanbul, Turkey
  • 7. NASA, Ames Res Ctr, Space Sci & Astrobiol Div, Moffett Field, CA 94035 USA
  • 8. Univ Hertfordshire, Ctr Astrophys Res, Hatfield AL10 9AB, Herts, England
  • 9. Max Planck Inst Extraterr Phys, D-85748 Garching, Germany
  • 10. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1090 GE Amsterdam, Netherlands
  • 11. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA

Description

We present our temporal and spectral analyses of 29 bursts from SGR J0501+4516, detected with the gamma-ray burst monitor on board the Fermi Gamma-ray Space Telescope during 13 days of the source's activation in 2008 (August 22-September 3). We find that the T-90 durations of the bursts can be fit with a log-normal distribution with a mean value of similar to 123 ms. We also estimate for the first time event durations of soft gamma repeater (SGR) bursts in photon space (i.e., using their deconvolved spectra) and find that these are very similar to the T-90 values estimated in count space (following a log-normal distribution with a mean value of similar to 124 ms). We fit the time-integrated spectra for each burst and the time-resolved spectra of the five brightest bursts with several models. We find that a single power law with an exponential cutoff model fits all 29 bursts well, while 18 of the events can also be fit with two blackbody functions. We expand on the physical interpretation of these two models and we compare their parameters and discuss their evolution. We show that the time-integrated and time-resolved spectra reveal that E-peak decreases with energy flux (and fluence) to a minimum of similar to 30 keV at F = 8.7 x 10(-6) erg cm(-2) s(-1), increasing steadily afterward. Two more sources exhibit a similar trend: SGRs J1550-5418 and 1806-20. The isotropic luminosity, L-iso, corresponding to these flux values is roughly similar for all sources (0.4-1.5 x 10(40) erg s(-1)).

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