Abstract

We report the first detection of high-energy X-ray (E > 10 keV) emission from the Galactic center non-thermal filament G359.89-0.08 (Sgr A-E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to similar to 50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index G approximate to 2.3 confirms a non-thermal emission mechanism. The observed flux in the 3-79 keV band is F-X = (2.0 +/- 0.1) x 10(-12) erg cm(-2) s(-1), corresponding to an unabsorbed X-ray luminosity L-X = (2.6 +/- 0.8) x 10(34) erg s(-1) assuming a distance of 8.0 kpc. Based on theoretical predictions and observations, we conclude that Sgr A-E is unlikely to be a pulsar wind nebula (PWN) or supernova remnant-molecular cloud (SNR-MC) interaction, as previously hypothesized. Instead, the emission could be due to a magnetic flux tube which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to similar to 100 kyr) with low surface brightness and radii up to similar to 30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.