VER J2227+608: A Hadronic PeVatron Pulsar Wind Nebula?. (arXiv:1907.04972v1 [astro-ph.HE])

VER J2227+608: A Hadronic PeVatron Pulsar Wind Nebula?. (arXiv:1907.04972v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Xin_Y/0/1/0/all/0/1">Yuliang Xin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zeng_H/0/1/0/all/0/1">Houdun Zeng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_S/0/1/0/all/0/1">Siming Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fan_Y/0/1/0/all/0/1">Yizhong Fan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wei_D/0/1/0/all/0/1">Daming Wei</a>

We report the detection of GeV $gamma$-ray emission from the
very-high-energy (VHE) $gamma$-ray source VER J2227+608 associated with the
“tail” region of SNR G106.3+2.7. The GeV $gamma$-ray emission is extended and
spatially coincident with molecular clouds traced by CO emission. The broadband
GeV to TeV emission of VER J2227+608 can be well fitted by a single power-law
function with an index of 1.90$pm$0.04, without obvious indication of spectral
cutoff toward high energies. The pure leptonic model for the $gamma$-ray
emission can be marginally ruled out by the X-ray and TeV data. In the hadronic
model, the low energy content of CRs and the hard $gamma$-ray spectrum suggest
that VER J2227+608 may be powered by the PWN instead of shocks of the SNR. And
the cutoff energy of the proton distribution needs to be higher than $sim$ 400
TeV, which makes it an attractive PeVatron candidate. Future observations by
the upcoming Large High Altitude Air Shower Observatory (LHAASO) and the
Cherenkov Telescope Array in the north (CTA-North) could distinguish these
models and constrain the maximum energy of cosmic rays in supernova remnants.

We report the detection of GeV $gamma$-ray emission from the
very-high-energy (VHE) $gamma$-ray source VER J2227+608 associated with the
“tail” region of SNR G106.3+2.7. The GeV $gamma$-ray emission is extended and
spatially coincident with molecular clouds traced by CO emission. The broadband
GeV to TeV emission of VER J2227+608 can be well fitted by a single power-law
function with an index of 1.90$pm$0.04, without obvious indication of spectral
cutoff toward high energies. The pure leptonic model for the $gamma$-ray
emission can be marginally ruled out by the X-ray and TeV data. In the hadronic
model, the low energy content of CRs and the hard $gamma$-ray spectrum suggest
that VER J2227+608 may be powered by the PWN instead of shocks of the SNR. And
the cutoff energy of the proton distribution needs to be higher than $sim$ 400
TeV, which makes it an attractive PeVatron candidate. Future observations by
the upcoming Large High Altitude Air Shower Observatory (LHAASO) and the
Cherenkov Telescope Array in the north (CTA-North) could distinguish these
models and constrain the maximum energy of cosmic rays in supernova remnants.

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