Discovery of a Magnetar Associated with the Soft Gamma Repeater SGR 1900+14

The soft gamma repeater SGR 1900+14 became active again on 1998 June after a long period of quiescence; it remained at a low state of activity until 1998 August, when it emitted a series of extraordinarily intense outbursts. We have observed the source with the Rossi X-Ray Timing Explorer twice, during the onset of each active episode. We confirm the pulsations at the 5.16 s period reported earlier from SGR 1900+14. Here we report the detection of a secular spin-down of the pulse period at an average rate of 1.1 × 10-10 s s-1. In view of the strong similarities between SGRs, we attribute the spin-down of SGR 1900+14 to magnetic dipole radiation, possibly accelerated by a quiescent flux, as in the case of SGR 1806-20. This allows an estimate of the pulsar dipolar magnetic field, which is (2–8) × 1014 G. Our results confirm that SGRs are magnetars.

[1]  C. Kouveliotou,et al.  Localization, time histories, and energy spectra of a new type of recurrent high-energy transient source , 1987 .

[2]  O. Blaes,et al.  Magnetohydrodynamics in the extreme relativistic limit , 1998 .

[3]  S. Barthelmy,et al.  RXTE quick response observations of afterglows from GRBs , 1998 .

[4]  D. Gruber,et al.  Discovery of a New 89 Second X-Ray Pulsar: XTE J1906+09 , 1998, astro-ph/9805354.

[5]  Lognormal properties of SGR 1806-20 and implications for other SGR sources , 1995, astro-ph/9508074.

[6]  Christopher Thompson,et al.  The Soft Gamma Repeaters as Very Strongly Magnetized Neutron Stars. II. Quiescent Neutrino, X-Ray, and Alfvén Wave Emission , 1996 .

[7]  C. Kouveliotou,et al.  SMM hard X-ray observations of the soft gamma-ray repeater 1806-20 , 1987 .

[8]  C. Thompson,et al.  The soft gamma repeaters as very strongly magnetized neutron stars - I. Radiative mechanism for outbursts , 1995 .

[9]  J.-L. Atteia,et al.  A new type of repetitive behavior in a high-energy transient , 1987 .

[10]  C. Kouveliotou.  SGR activity and global characteristics , 1995 .

[11]  R. Guyer,et al.  Earthquake-like behaviour of soft γ-ray repeaters , 1996, Nature.

[12]  D. Frail,et al.  Radio monitoring and high-resolution imaging of the soft gamma-ray repeater 1806-20 , 1995, astro-ph/9411117.

[13]  S. V. Golenetskii,et al.  Observations of a flaring X-ray pulsar in Dorado , 1979, Nature.

[14]  E. Mazets,et al.  Reactivation and Precise Interplanetary Network Localization of the Soft Gamma Repeater SGR 1900+14 , 1998, astro-ph/9811411.

[15]  D. Frail,et al.  SUPERNOVA REMNANT CANDIDATES FOR THE SOFT GAMMA -RAY REPEATER 1900+14 , 1994 .

[16]  T. Lu,et al.  High velocity neutron stars and gamma-ray bursts , 1996 .

[17]  C. Kouveliotou,et al.  Network synthesis localization of two soft gamma repeaters , 1994 .

[18]  Christopher Thompson,et al.  Formation of very strongly magnetized neutron stars - Implications for gamma-ray bursts , 1992 .

[19]  K. Hurley,et al.  An X-ray pulsar with a superstrong magnetic field in the soft γ-ray repeater SGR1806 − 20 , 1998, Nature.

[20]  C. Kouveliotou,et al.  The rarity of soft γ-ray repeaters deduced from reactivation of SGR1806 – 20 , 1994, Nature.