Non-thermal emission from young supernova remnants in dense circumstellar environments. (arXiv:2109.04828v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Brose_R/0/1/0/all/0/1">Robert Brose</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mackey_J/0/1/0/all/0/1">Jonathan Mackey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sushch_I/0/1/0/all/0/1">Iurii Sushch</a>
Supernova remnants are known to accelerate cosmic rays (CRs) on account of
their non-thermal emission of radio waves, X-rays, and gamma rays. However, the
ability to accelerate CRs up to PeV-energies has yet to be demonstrated. The
presence of cut-offs in the gamma-ray spectra of several young SNRs led to the
idea that PeV energies might only be achieved during the very initial stages of
a remnant’s evolution. We use the time-dependent acceleration code RATPaC to
study the acceleration of cosmic rays in supernovae expanding into dense
environments around massive stars, where the plentiful target material might
offer a path to the detection of gamma-rays by current and future experiments.
We performed spherically symmetric 1-D simulations in which we simultaneously
solve the transport equations for cosmic rays, magnetic turbulence, and the
hydrodynamical flow of the thermal plasma in the test-particle limit. We
investigated typical parameters of the circumstellar medium (CSM) in the freely
expanding winds around red supergiant (RSG) and luminous blue variable (LBV)
stars. The maximum achievable energy might be limited to sub-PeV energies
despite strong magnetic fields close to the progenitor star that enhance
turbulence-damping by cascading: we find a maximum CR energy of 100-200 TeV,
reached within one month after explosion. The peak luminosity for a LBV
progenitor is 1e43 erg/s (1e42 erg/s) at GeV (TeV) energies and, for a RSG
progenitor, 1e41 erg/s (1e40 erg/s). All calculated SNe reach their peak
gamma-ray luminosity after <~1 month and then fade at a rate ~1/t as long as
the SN shock remains in the freely expanding wind of the progenitor.
Potentially detectable gamma-ray signals can be expected in the Fermi-LAT
waveband weeks to months after an explosion into a freely expanding wind.
Supernova remnants are known to accelerate cosmic rays (CRs) on account of
their non-thermal emission of radio waves, X-rays, and gamma rays. However, the
ability to accelerate CRs up to PeV-energies has yet to be demonstrated. The
presence of cut-offs in the gamma-ray spectra of several young SNRs led to the
idea that PeV energies might only be achieved during the very initial stages of
a remnant’s evolution. We use the time-dependent acceleration code RATPaC to
study the acceleration of cosmic rays in supernovae expanding into dense
environments around massive stars, where the plentiful target material might
offer a path to the detection of gamma-rays by current and future experiments.
We performed spherically symmetric 1-D simulations in which we simultaneously
solve the transport equations for cosmic rays, magnetic turbulence, and the
hydrodynamical flow of the thermal plasma in the test-particle limit. We
investigated typical parameters of the circumstellar medium (CSM) in the freely
expanding winds around red supergiant (RSG) and luminous blue variable (LBV)
stars. The maximum achievable energy might be limited to sub-PeV energies
despite strong magnetic fields close to the progenitor star that enhance
turbulence-damping by cascading: we find a maximum CR energy of 100-200 TeV,
reached within one month after explosion. The peak luminosity for a LBV
progenitor is 1e43 erg/s (1e42 erg/s) at GeV (TeV) energies and, for a RSG
progenitor, 1e41 erg/s (1e40 erg/s). All calculated SNe reach their peak
gamma-ray luminosity after <~1 month and then fade at a rate ~1/t as long as
the SN shock remains in the freely expanding wind of the progenitor.
Potentially detectable gamma-ray signals can be expected in the Fermi-LAT
waveband weeks to months after an explosion into a freely expanding wind.
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