TY - JOUR
T1 - High-energy X-ray imaging of the pulsar wind nebula MSH 15-52: constraints on particle acceleration and transport
AU - An, Hongjun
AU - Madsen, Kristin K.
AU - Reynolds, Stephen P.
AU - Kaspi, Victoria M.
AU - Harrison, Fiona A.
AU - Boggs, Steven E.
AU - Christensen, Finn Erland
AU - Craig, William W.
AU - Fryer, Chris L.
AU - Grefenstette, Brian W.
AU - Hailey, Charles J.
AU - Mori, Kaya
AU - Stern, Daniel
AU - Zhang, William W.
PY - 2014
Y1 - 2014
N2 - We present the first images of the pulsar wind nebula (PWN) MSH 15−52 in the hard X-ray band (8 keV), as
measured with the Nuclear Spectroscopic Telescope Array (NuSTAR). Overall, the morphology of the PWN as
measured by NuSTAR in the 3–7 keV band is similar to that seen in Chandra high-resolution imaging. However, the
spatial extent decreases with energy, which we attribute to synchrotron energy losses as the particles move away
from the shock. The hard-band maps show a relative deficit of counts in the northern region toward the RCW 89
thermal remnant, with significant asymmetry.We find that the integrated PWN spectra measured with NuSTAR and
Chandra suggest that there is a spectral break at 6 keV, which may be explained by a break in the synchrotron-emitting
electron distribution at ∼200 TeV and/or imperfect cross calibration. We also measure spatially resolved
spectra, showing that the spectrum of the PWN softens away from the central pulsar B1509−58, and that there
exists a roughly sinusoidal variation of spectral hardness in the azimuthal direction. We discuss the results using
particle flow models.We find non-monotonic structure in the variation with distance of spectral hardness within 50
of the pulsar moving in the jet direction, which may imply particle and magnetic-field compression by magnetic
hoop stress as previously suggested for this source. We also present two-dimensional maps of spectral parameters
and find an interesting shell-like structure in the NH map.We discuss possible origins of the shell-like structure and
their implications.
AB - We present the first images of the pulsar wind nebula (PWN) MSH 15−52 in the hard X-ray band (8 keV), as
measured with the Nuclear Spectroscopic Telescope Array (NuSTAR). Overall, the morphology of the PWN as
measured by NuSTAR in the 3–7 keV band is similar to that seen in Chandra high-resolution imaging. However, the
spatial extent decreases with energy, which we attribute to synchrotron energy losses as the particles move away
from the shock. The hard-band maps show a relative deficit of counts in the northern region toward the RCW 89
thermal remnant, with significant asymmetry.We find that the integrated PWN spectra measured with NuSTAR and
Chandra suggest that there is a spectral break at 6 keV, which may be explained by a break in the synchrotron-emitting
electron distribution at ∼200 TeV and/or imperfect cross calibration. We also measure spatially resolved
spectra, showing that the spectrum of the PWN softens away from the central pulsar B1509−58, and that there
exists a roughly sinusoidal variation of spectral hardness in the azimuthal direction. We discuss the results using
particle flow models.We find non-monotonic structure in the variation with distance of spectral hardness within 50
of the pulsar moving in the jet direction, which may imply particle and magnetic-field compression by magnetic
hoop stress as previously suggested for this source. We also present two-dimensional maps of spectral parameters
and find an interesting shell-like structure in the NH map.We discuss possible origins of the shell-like structure and
their implications.
U2 - 10.1088/0004-637X/793/2/90
DO - 10.1088/0004-637X/793/2/90
M3 - Journal article
SN - 0004-637X
VL - 793
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 90
ER -