The growth, polarization, and motion of the radio afterglow from the giant flare from SGR 1806-20

G. B. Taylor, Joseph (Yosi) Gelfand, B. M. Gaensler, J. Granot, C. Kouveliotou, R. P. Fender, E. Ramirez-Ruiz, D. Eichler, Y. E. Lyubarsky, M. Garrett, R. A.M.J. Wijers

Research output: Contribution to journalArticle

Abstract

The extraordinary giant flare (GF) of 2004 December 27 from the soft gamma repeater SGR 1806-20 was followed by a bright radio afterglow. We present an analysis of VLA observations of this radio afterglow from SGR 1806-20, consisting of previously reported 8.5 GHz data covering days 7-20 after the GF, plus new observations at 8.5 and 22 GHz from day 24 to 81. We detect motion in the flux centroid of the afterglow, at an average velocity of (0.26 ± 0.03)c (assuming a distance of 15 kpc) at a position angle of -45°. This motion, in combination with the growth and polarization measurements, suggests an asymmetric outflow, mainly from one side of the magnetar. We find a deceleration in the expansion, from ∼9 to <5 mas day-1. The time of deceleration is roughly coincident with the rebrightening in the radio light curve, as expected to result when the ejecta from the GF sweeps up enough of the external medium and transitions from a coasting phase to the Sedov-Taylor regime. The radio afterglow is elongated and maintains a 2 : 1 axis ratio with an average position angle of -40° (north through east), oriented perpendicular to the average intrinsic linear polarization angle.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume634
Issue number1 II
DOIs
StatePublished - Nov 20 2005

Fingerprint

afterglows
flares
polarization
radio
deceleration
soft gamma repeaters
magnetars
ejecta
linear polarization
centroids
light curve
coverings
outflow
expansion

Keywords

  • Pulsars: individual (SGR 1806-20)
  • Radio continuum: general
  • Stars: flare
  • Stars: neutron
  • Stars: winds, outflows

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Taylor, G. B., Gelfand, J. Y., Gaensler, B. M., Granot, J., Kouveliotou, C., Fender, R. P., ... Wijers, R. A. M. J. (2005). The growth, polarization, and motion of the radio afterglow from the giant flare from SGR 1806-20. Astrophysical Journal, 634(1 II). https://doi.org/10.1086/491648

The growth, polarization, and motion of the radio afterglow from the giant flare from SGR 1806-20. / Taylor, G. B.; Gelfand, Joseph (Yosi); Gaensler, B. M.; Granot, J.; Kouveliotou, C.; Fender, R. P.; Ramirez-Ruiz, E.; Eichler, D.; Lyubarsky, Y. E.; Garrett, M.; Wijers, R. A.M.J.

In: Astrophysical Journal, Vol. 634, No. 1 II, 20.11.2005.

Research output: Contribution to journalArticle

Taylor, GB, Gelfand, JY, Gaensler, BM, Granot, J, Kouveliotou, C, Fender, RP, Ramirez-Ruiz, E, Eichler, D, Lyubarsky, YE, Garrett, M & Wijers, RAMJ 2005, 'The growth, polarization, and motion of the radio afterglow from the giant flare from SGR 1806-20', Astrophysical Journal, vol. 634, no. 1 II. https://doi.org/10.1086/491648
Taylor, G. B. ; Gelfand, Joseph (Yosi) ; Gaensler, B. M. ; Granot, J. ; Kouveliotou, C. ; Fender, R. P. ; Ramirez-Ruiz, E. ; Eichler, D. ; Lyubarsky, Y. E. ; Garrett, M. ; Wijers, R. A.M.J. / The growth, polarization, and motion of the radio afterglow from the giant flare from SGR 1806-20. In: Astrophysical Journal. 2005 ; Vol. 634, No. 1 II.
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