NuSTAR study of hard X-ray morphology and spectroscopy of PWN G21.5–0.9

Journal Article · Tue Jul 01 00:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/789/1/72· OSTI ID:22356450

Nynka, Melania; Hailey, Charles J.; Gotthelf, Eric V.; Mori, Kaya; Perez, Kerstin ^[1]; Reynolds, Stephen P. ^[2]; An, Hongjun ^[3]; Baganoff, Frederick K. ^[4]; Boggs, Steven E.; Krivonos, Roman; Zoglauer, Andreas ^[5]; Christensen, Finn E. ^[6]; Craig, William W. ^[7]; Grefenstette, Brian W.; Harrison, Fiona A.; Madsen, Kristin K. ^[8]; Stern, Daniel ^[9]; Wik, Daniel R.; Zhang, William W. ^[10]

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1. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
2. Physics Department, NC State University, Raleigh, NC 27695 (United States)
3. Department of Physics, McGill University, Rutherford Physics Building, 3600 University Street, Montreal, Quebec H3A 2T8 (Canada)
4. Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139-4307 (United States)
5. Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
6. DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
7. Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States)
8. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)
9. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
10. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

We present NuSTAR high-energy X-ray observations of the pulsar wind nebula (PWN)/supernova remnant G21.5–0.9. We detect integrated emission from the nebula up to ∼40 keV, and resolve individual spatial features over a broad X-ray band for the first time. The morphology seen by NuSTAR agrees well with that seen by XMM-Newton and Chandra below 10 keV. At high energies, NuSTAR clearly detects non-thermal emission up to ∼20 keV that extends along the eastern and northern rim of the supernova shell. The broadband images clearly demonstrate that X-ray emission from the North Spur and Eastern Limb results predominantly from non-thermal processes. We detect a break in the spatially integrated X-ray spectrum at ∼9 keV that cannot be reproduced by current spectral energy distribution models, implying either a more complex electron injection spectrum or an additional process such as diffusion compared to what has been considered in previous work. We use spatially resolved maps to derive an energy-dependent cooling length scale, L(E)∝E{sup m} with m = –0.21 ± 0.01. We find this to be inconsistent with the model for the morphological evolution with energy described by Kennel and Coroniti. This value, along with the observed steepening in power-law index between radio and X-ray, can be quantitatively explained as an energy-loss spectral break in the simple scaling model of Reynolds, assuming particle advection dominates over diffusion. This interpretation requires a substantial departure from spherical magnetohydrodynamic, magnetic-flux-conserving outflow, most plausibly in the form of turbulent magnetic-field amplification.

• OSTI ID: 22356450
• Journal Information: Astrophysical Journal, Vol. 789, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
DIFFUSION
ELECTRON BEAM INJECTION
EMISSION
ENERGY DEPENDENCE
ENERGY SPECTRA
EVOLUTION
HARD X RADIATION
KEV RANGE
MAGNETIC FIELDS
MAGNETIC FLUX
MAGNETOHYDRODYNAMICS
NEBULAE
PULSARS
RESONANCE IONIZATION MASS SPECTROSCOPY
REYNOLDS NUMBER
SPHERICAL CONFIGURATION
STARS
SUPERNOVA REMNANTS
X-RAY SPECTRA