Early-time gamma-ray constraints on cosmic-ray acceleration in the core-collapse SN 2023ixf with the Fermi Large Area Telescope
arxiv(2024)
摘要
While SNRs have been considered the most relevant Galactic CR accelerators
for decades, CCSNe could accelerate particles during the earliest stages of
their evolution and hence contribute to the CR energy budget in the Galaxy.
Some SNRs have indeed been associated with TeV gamma-rays, yet proton
acceleration efficiency during the early stages of an SN expansion remains
mostly unconstrained. The multi-wavelength observation of SN 2023ixf, a Type II
SN in the nearby galaxy M101, opens the possibility to constrain CR
acceleration within a few days after the collapse of the RSG stellar
progenitor. With this work, we intend to provide a phenomenological,
quasi-model-independent constraint on the CR acceleration efficiency during
this event at photon energies above 100 MeV. We performed a maximum-likelihood
analysis of gamma-ray data from the Fermi Large Area Telescope up to one month
after the SN explosion. We searched for high-energy emission from its expanding
shock, and estimated the underlying hadronic CR energy reservoir assuming a
power-law proton distribution consistent with standard diffusive shock
acceleration. We do not find significant gamma-ray emission from SN 2023ixf.
Nonetheless, our non-detection provides the first limit on the energy
transferred to the population of hadronic CRs during the very early expansion
of a CCSN. Under reasonable assumptions, our limits would imply a maximum
efficiency on the CR acceleration of as low as 1
the common estimate of 10
dependent on the assumed geometry of the circumstellar medium, and could be
relaxed back to 10
inhomogeneous characterisation of the shock and the progenitor's environment is
required before establishing whether or not Type II SNe are indeed efficient CR
accelerators at early times.
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