HIGH-ENERGY X-RAY DETECTION OF G359.89−0.08 (SGR A−E): MAGNETIC FLUX TUBE EMISSION POWERED BY COSMIC RAYS?

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 ∼50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index Γ ≈ 2.3 confirms a non-thermal emission mechanism. The observed flux in the 3–79 keV band is FX = (2.0 ± 0.1) × 10−12 erg cm−2 s−1, corresponding to an unabsorbed X-ray luminosity LX = (2.6 ± 0.8) × 1034 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 ∼100 kyr) with low surface brightness and radii up to ∼30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.

[1]  F. Christensen,et al.  HIGH-ENERGY X-RAYS FROM J174545.5–285829, THE CANNONBALL: A CANDIDATE PULSAR WIND NEBULA ASSOCIATED WITH Sgr A EAST , 2013, 1311.1832.

[2]  Kristin K. Madsen,et al.  NuSTAR DISCOVERY OF A 3.76 s TRANSIENT MAGNETAR NEAR SAGITTARIUS A* , 2013, 1305.1945.

[3]  William W. Zhang,et al.  THE NUCLEAR SPECTROSCOPIC TELESCOPE ARRAY (NuSTAR) HIGH-ENERGY X-RAY MISSION , 2013, Astronomical Telescopes and Instrumentation.

[4]  L. Zhang,et al.  NONTHERMAL EMISSION FROM MIDDLE-AGED SUPERNOVA REMNANTS INTERACTING WITH MOLECULAR CLOUDS , 2011 .

[5]  D. Hooper,et al.  DARK MATTER AND SYNCHROTRON EMISSION FROM GALACTIC CENTER RADIO FILAMENTS , 2011, 1106.5493.

[6]  R. Yamazaki,et al.  X-RAY EVOLUTION OF PULSAR WIND NEBULAE , 2010, 1007.3203.

[7]  Q. Wang,et al.  A large-scale survey of X-ray filaments in the Galactic Centre , 2009, 0910.4944.

[8]  F. Aharonian,et al.  Broad-band non-thermal emission from molecular clouds illuminated by cosmic rays from nearby supernova remnants , 2009, 0901.4549.

[9]  P. S. Bunclark,et al.  Astronomical Data Analysis Software and Systems , 2008 .

[10]  O. Kargaltsev,et al.  Pulsar Wind Nebulae in the Chandra Era , 2008, 0801.2602.

[11]  T. Yuan,et al.  An Imaging and Spectral Study of 10 X-Ray Filaments around the Galactic Center , 2007, 0710.2668.

[12]  J. Starck,et al.  A Catalog of Diffuse X-Ray-emitting Features within 20 pc of Sagittarius A*: Twenty Pulsar Wind Nebulae? , 2007, 0707.1907.

[13]  Andrew Cumming,et al.  40 Years of Pulsars : Millisecond Pulsars, Magnetars and More , 2008 .

[14]  O. Kargaltsev,et al.  X-Ray Emission from PSR J1809–1917 and Its Pulsar Wind Nebula, Possibly Associated with the TeV Gamma-Ray Source HESS J1809–193 , 2007, 0705.2378.

[15]  Jean-Luc Starck,et al.  Astronomical Data Analysis , 2007 .

[16]  A. R. Bazer-Bachi,et al.  Discovery of Very-High-Energy Gamma-Rays from the Galactic Centre Ridge , 2006, astro-ph/0603021.

[17]  S. Boldyrev,et al.  Turbulent Origin of the Galactic Center Magnetic Field: Nonthermal Radio Filaments , 2005, astro-ph/0512373.

[18]  F. Aharonian,et al.  TeV Gamma Rays From the Galactic Center Direct and Indirect Links to the Massive Black Hole in Sgr A , 2005 .

[19]  W. Cotton,et al.  A 20 Centimeter Survey of the Galactic Center Region. I. Detection of Numerous Linear Filaments , 2004, astro-ph/0409292.

[20]  H. Lesch,et al.  In situ acceleration in the Galactic Center Arc , 2004, astro-ph/0402595.

[21]  MIT,et al.  Diffuse X-Ray Emission in a Deep Chandra Image of the Galactic Center , 2004, astro-ph/0402087.

[22]  C. Lang,et al.  The Chandra Detection of Galactic Center X-Ray Features G359.89−0.08 and G359.54+0.18 , 2003, astro-ph/0304101.

[23]  A. Decourchelle,et al.  The discovery of a new non-thermal X-ray filament near the Galactic Centre , 2002, astro-ph/0211572.

[24]  R. McCray,et al.  Astrophysical Journal, in press Preprint typeset using L ATEX style emulateapj v. 26/01/00 ON THE ABSORPTION OF X-RAYS IN THE INTERSTELLAR MEDIUM , 2000 .

[25]  R. Chevalier,et al.  Nonthermal Emission from a Supernova Remnant in a Molecular Cloud , 2000 .

[26]  A. Coil,et al.  The Dynamics of Molecular Material within 15 Parsecs of the Galactic Center , 1999, astro-ph/9910043.

[27]  The Astrophysical Journal , 2000 .

[28]  C. Lang,et al.  A Radio Polarimetric Study of the Galactic Center Threads , 1999, astro-ph/9906336.

[29]  D. A. Verner,et al.  Atomic data for astrophysics. II. New analytic fits for photoionization cross sections of atoms and ions , 1996 .

[30]  K. R. Anantharamaiah,et al.  Radio studies of the Galactic center. I. The Sagittarius A complex , 1989 .

[31]  Mark R. Morris,et al.  Structural details of the Sagittarius A complex - evidence for a large-scale poloidal magnetic field in the Galactic center region , 1987 .

[32]  M. Inoue,et al.  Prominent polarized plumes in the Galactic Center region and their magnetic field. , 1986 .

[33]  A. H. Barrett,et al.  Interactions between the continuum sources in the galactic center and their immediate molecular environment , 1985 .

[34]  M. Morris,et al.  Large, highly organized radio structures near the galactic centre , 1984, Nature.

[35]  C. Kennel,et al.  Confinement of the Crab pulsar's wind by its supernova remnant , 1984 .