Nynka, Melania10; Hailey, Charles J.10; Mori, Kaya10; Baganoff, Frederick K.11; Bauer, Franz E.5; Boggs, Steven E.12; Craig, William W.12; Christensen, Finn Erland1; Gotthelf, Eric V.10; Harrison, Fiona A.13; Hong, Jaesub8; Perez, Kerstin M.10; Stern, Daniel13; Shuo Zhang10; Zhang, William W.14
1 National Space Institute, Technical University of Denmark2 Astrophysics, National Space Institute, Technical University of Denmark3 Columbia University4 Massachusetts Institute of Technology5 Pontifícia Universidade Católica6 University of California at Berkeley7 California Institute of Technology8 Harvard-Smithsonian Center for Astrophysics9 NASA Goddard Space Flight Center10 Columbia University11 Massachusetts Institute of Technology12 University of California at Berkeley13 California Institute of Technology14 NASA Goddard Space Flight Center
We report the unambiguous detection of non-thermal X-ray emission up to 30 keV from the Cannonball, a few-arcsecond long diffuse X-ray feature near the Galactic Center, using the NuSTAR X-ray observatory. The Cannonball is a high-velocity ( v proj ~ 500 km s-1) pulsar candidate with a cometary pulsar wind nebula (PWN) located ~ 2' north-east from Sgr A*, just outside the radio shell of the supernova remnant Sagittarius A (Sgr A) East. Its non-thermal X-ray spectrum, measured up to 30 keV, is well characterized by a Γ ~ 1.6 power law, typical of a PWN, and has an X-ray luminosity of L (3-30 keV) = 1.3 × 1034 erg s-1 . The spectral and spatial results derived from X-ray and radio data strongly suggest a runaway neutron star born in the Sgr A East supernova event. We do not find any pulsed signal from the Cannonball. The NuSTAR observations allow us to deduce the PWN magnetic field and show that it is consistent with the lower limit obtained from radio observations.