NuSTAR DISCOVERY OF A 3.76 s TRANSIENT MAGNETAR NEAR SAGITTARIUS A*

Journal Article · Thu Jun 20 00:00:00 EDT 2013 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/770/2/L23· OSTI ID:22118779

Mori, Kaya; Gotthelf, Eric V.; Shuo, Zhang; Beloborodov, Andrei M.; Hailey, Charles J.; Nynka, Melania ^[1]; Hongjun, An; Dufour, Francois; Kaspi, Victoria M. ^[2]; Baganoff, Frederick K. ^[3]; Barriere, Nicolas M.; Boggs, Steven E.; Craig, William W. ^[4]; Christensen, Finn E. ^[5]; Grefenstette, Brian W.; Harrison, Fiona A.; Madsen, Kristin K. ^[6]; Hong, Jaesub ^[7]; Kennea, Jamie A. ^[8]; others, and

---

1. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
2. Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada)
3. Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
4. Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
5. DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Lyngby (Denmark)
6. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)
7. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
8. Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)

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 P-dot =(6.5 {+-} 1.4) Multiplication-Sign 10{sup -12}. This implies a magnetic field B = 1.6 Multiplication-Sign 10{sup 14} G, spin-down power E-dot =5 Multiplication-Sign 10{sup 33} erg s{sup -1}, and characteristic age P/2 P-dot =9 Multiplication-Sign 10{sup 3} yr for the rotating dipole model. However, the current P-dot 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{sub BB} = 0.96 {+-} 0.02 keV and photon index {Gamma} = 1.5 {+-} 0.4. The neutral hydrogen column density (N{sub H} {approx} 1.4 Multiplication-Sign 10{sup 23} cm{sup -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{sub x} {approx}< 10{sup 32} erg s{sup -1}. The bursting, timing, and spectral properties indicate a transient magnetar undergoing an outburst with 2-79 keV luminosity up to 3.5 Multiplication-Sign 10{sup 35} erg s{sup -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.

• OSTI ID: 22118779
• Journal Information: Astrophysical Journal Letters, Vol. 770, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASTRONOMY
ASTROPHYSICS
CATALOGS
COSMIC PHOTONS
DISTANCE
EMISSION SPECTRA
HYDROGEN
INDEXES
INTERSTELLAR MAGNETIC FIELDS
KEV RANGE
LUMINOSITY
MAGNETIC STARS
MILKY WAY
NEUTRON STARS
PULSARS
PULSATIONS
SPIN
TRANSIENTS
X RADIATION
X-RAY SPECTRA