CaltechAUTHORS
Published February 20, 2010 | Version Published + Erratum
Journal Article Open

Magnetar Twists: Fermi/Gamma-Ray Burst Monitor Detection of SGR J1550-5418

Creators

  • 1. ROR icon Marshall Space Flight Center
  • 2. ROR icon University of Hertfordshire
  • 3. ROR icon University of California, Santa Cruz
  • 4. ROR icon University of Amsterdam
  • 5. ROR icon National Space Science and Technology Center
  • 6. ROR icon Goddard Space Flight Center
  • 7. ROR icon Space Telescope Science Institute
  • 8. ROR icon Max Planck Institute for Extraterrestrial Physics
  • 9. ROR icon California Institute of Technology
  • 10. ROR icon Dynetics (United States)

Abstract

SGR J1550-5418 (previously known as AXP 1E 1547.0-5408 or PSR J1550-5418) went into three active bursting episodes in 2008 October and in 2009 January and March, emitting hundreds of typical soft gamma repeater bursts in soft gamma rays. The second episode was especially intense, and our untriggered burst search on Fermi/Gamma-ray Burst Monitor (GBM) data (8-1000 keV) revealed ~450 bursts emitted over 24 hr during the peak of this activity. Using the GBM data, we identified a ~150 s long enhanced persistent emission during 2009 January 22 that exhibited intriguing timing and spectral properties: (1) clear pulsations up to ~110 keV at the spin period of the neutron star (P ~ 2.07 s, the fastest of all magnetars); (2) an additional (to a power-law) blackbody component required for the enhanced emission spectra with kT ~ 17 keV; and (3) pulsed fraction that is strongly energy dependent and highest in the 50-74 keV energy band. A total isotropic-equivalent energy emitted during this enhanced emission is estimated to be 2.9 × 10^(40)(D/5 kpc)^2 erg. The estimated area of the blackbody emitting region of ≈0.046(D/5 kpc)^2 km^2 (roughly a few ×10^(–5) of the neutron star area) is the smallest "hot spot" ever measured for a magnetar and most likely corresponds to the size of magnetically confined plasma near the neutron star surface.

Additional Information

© 2010 American Astronomical Society. Print publication: Issue 2 (2010 February 20); received 2009 December 11; accepted for publication 2009 December 22; published 2010 January 29. We thank the referee, Dr. F. Camilo, for his valuable comments. This publication is part of the GBM/Magnetar Key Project (NASA grant NNH07ZDA001-GLAST, PI: C. Kouveliotou). We thank G. L. Israel and A. Tiengo for providing the precise spin ephemeris and source distance, respectively, prior to their publication. Y.K. and E.G. acknowledge EU FP6 Transfer of Knowledge Project "Astrophysics of Neutron Stars" (MTKD-CT-2006-042722). J.G. gratefully acknowledges a Royal Society Wolfson Research Merit Award. E. R.-R. thanks the Packard Foundation for support. A.J.v.d.H. was supported by an appointment to the NASA Postdoctoral Program at the MSFC, administered by Oak Ridge Associated Universities through a contract with NASA.

Attached Files

Published - Kaneko2010p7146Astrophys_J.pdf

Erratum - Kaneko2010p7393Astrophys_J.pdf

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Additional details

Identifiers

Eprint ID
17659
Resolver ID
CaltechAUTHORS:20100304-100001944

Funding

NASA
NNH07ZDA001-GLAST
European Research Council (ERC)
MTKD-CT-2006-042722
Royal Society
David and Lucile Packard Foundation
NASA Postdoctoral Program

Dates

Created
2010-03-04
Created from EPrint's datestamp field
Updated
2021-11-08
Created from EPrint's last_modified field