Multiwavelength Investigation of Pulsar Wind Nebula DA 495 with HAWC, VERITAS, and NuSTAR. (arXiv:1905.07327v1 [astro-ph.HE])

Multiwavelength Investigation of Pulsar Wind Nebula DA 495 with HAWC, VERITAS, and NuSTAR. (arXiv:1905.07327v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Coerver_A/0/1/0/all/0/1">A. Coerver</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Wilcox_P/0/1/0/all/0/1">P. Wilcox</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_H/0/1/0/all/0/1">H. Zhang</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Dingus_B/0/1/0/all/0/1">B. L. Dingus</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Gotthelf_E/0/1/0/all/0/1">E. V. Gotthelf</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Hailey_C/0/1/0/all/0/1">C. J. Hailey</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Humensky_T/0/1/0/all/0/1">T. B. Humensky</a> (6), <a href="http://arxiv.org/find/astro-ph/1/au:+Kaaret_P/0/1/0/all/0/1">P. Kaaret</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_H/0/1/0/all/0/1">H. Li</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Mori_K/0/1/0/all/0/1">K. Mori</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Mukherjee_R/0/1/0/all/0/1">R. Mukherjee</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Park_N/0/1/0/all/0/1">N. Park</a> (7), <a href="http://arxiv.org/find/astro-ph/1/au:+Zhou_H/0/1/0/all/0/1">H. Zhou</a> (4) ((1) Department of Physics and Astronomy, Barnard College, Columbia University, NY, (2) Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA, (3) Department of Physics and Astronomy, Purdue University, West Lafayette, IN, (4) Los Alamos National Laboratory, Los Alamos, NM, (5) Columbia Astrophysics Laboratory, Columbia University, NY, (6) Physics Department, Columbia University, NY, (7) Los Alamos National Laboratory, Los Alamos, NM, USA)

Pulsar Wind Nebula (PWN) DA 495 (G65.7+1.2) was detected in TeV gamma-rays by
the High Altitude Water Cherenkov Observatory (HAWC) in 2017 (2HWC J1953+294).
Follow-up observations by the Very Energetic Radiation Imaging Telescope Array
System (VERITAS) confirmed the association between 2HWC J1953+294 and DA 495
and found the TeV emission to be spatially coincident with the radio emission
first reported in 1968. The detection of TeV gamma-rays from DA 495, along with
past X-ray detection up to 10 keV, prompted high energy X-ray observations as
part of the NuSTAR Galactic Legacy Survey. We present the results of these
NuSTAR observations, combined with archival Chandra and XMM-Newton
observations, and confirm the previous X-ray photon index of $Gamma_{2-20 rm
keV} = 2.0 pm 0.1$. We find no spectral cutoff up to 20 keV. With the spectral
information for DA 495 extended to TeV gamma-rays, we were able to perform
analytical modeling to test leptonic and hadronic emission scenarios. The
leptonic models can explain the broadband emission, but also imply a diffuse
X-ray nebula of similar extent to the radio and TeV nebulae, which cannot be
confirmed by our observations. The hadronic models can simultaneously explain
the spectrum and the spatial extent in all wavelengths; however, we need a very
high magnetic field strength pervading the radio and TeV nebulae and a
surprisingly high particle kinetic energy. These requirements deepen the
mystery of the physical nature of DA 495. Future observations in radio to
infrared bands and spatially resolved $gamma$-rays can further constrain the
physical conditions and radiation mechanisms in DA 495.

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