NuSTAR DISCOVERY OF A 3.76 s TRANSIENT MAGNETAR NEAR SAGITTARIUS A*
We report the discovery of 3.76 s pulsations from a new burst source near Sgr A* observed by the NuSTAR observatory. The strong signal from SGR J1745-29 presents a complex pulse profile modulated with pulsed fraction 27% ± 3% in the 3-10 keV band. Two observations spaced nine days apart yield a spin...
Main Authors: | , , , , , , , , , , , , , , , , , , , , , , |
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Other Authors: | , |
Format: | Article |
Language: | English |
Published: |
IOP Publishing,
2015-02-03T19:58:46Z.
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Online Access: | Get fulltext |
Summary: | We report the discovery of 3.76 s pulsations from a new burst source near Sgr A* observed by the NuSTAR observatory. The strong signal from SGR J1745-29 presents a complex pulse profile modulated with pulsed fraction 27% ± 3% in the 3-10 keV band. Two observations spaced nine days apart yield a spin-down rate of [dot over P] = (6.5 ± 1.4) × 10[superscipt -12]. This implies a magnetic field B = 1.6 × 10[superscript 14] G, spin-down power [dot over E] = 5 × 10[superscript 33] erg s[superscript -1], and characteristic age P/2 [dot over P] = 9 × 10[superscript 3] yr for the rotating dipole model. However, the current [dot over P] may be erratic, especially during outburst. The flux and modulation remained steady during the observations and the 3-79 keV spectrum is well fitted by a combined blackbody plus power-law model with temperature kT [subscript BB] = 0.96 ± 0.02 keV and photon index Γ = 1.5 ± 0.4. The neutral hydrogen column density (N [subscript H] ~ 1.4 × 10[superscript 23] cm[superscript -2]) measured by NuSTAR and Swift suggests that SGR J1745-29 is located at or near the Galactic center. The lack of an X-ray counterpart in the published Chandra survey catalog sets a quiescent 2-8 keV luminosity limit of L[subscript x] [< over ~] 10[superscript 32] erg s[superscript -1]. The bursting, timing, and spectral properties indicate a transient magnetar undergoing an outburst with 2-79 keV luminosity up to 3.5 × 1035 erg s-1 for a distance of 8 kpc. SGR J1745-29 joins a growing subclass of transient magnetars, indicating that many magnetars in quiescence remain undetected in the X-ray band or have been detected as high-B radio pulsars. The peculiar location of SGR J1745-29 has important implications for the formation and dynamics of neutron stars in the Galactic center region. United States. National Aeronautics and Space Administration (Contract NNG08FD60C) |
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