Coline Dubos | Searcharxiv

arXiv2024

Cherenkov Telescope Array Observatory sensitivity to heavy Galactic Cosmic Rays and the shape of particle spectrum

The origin of Galactic Cosmic Rays (GCRs) and the potential role of Supernova Remnants (SNRs) as cosmic-ray (CR) accelerators remain subjects of ongoing debate. To shed more light on this topic, we have studied the spectral shape of two SNRs, RX J1713.7-3946 and HAWC J2227+610, performing simulations for the Cherenkov Telescope Array Observatory (CTAO). The previous multi-wavelength (MWL) analysis on these two sources showed an important hadronic contribution at high energies. The interaction of the GCRs accelerated by the SNRs with the medium around the accelerator leads to a process of pion decay (PD) that produces gamma-rays ($\gamma$-rays). These emissions, detectable by CTAO, offer an indirect means of pinpointing the CR source. Two scenarios have been considered: the contribution of heavy CRs and different cut-off sharpnesses ($\beta$) of the particle spectra. The simulations were performed by using different CR composition distributions (protons, CNO, Fe) and different sharpness values ranging from $\beta$=0.5 to $\beta$=1.5. The results show that, in the cases studied here, CTAO will increase the sensitivity to the spectral shape of $\gamma$-rays. This allows us to distinguish protons from heavy CRs and obtain information on $\beta$ values and therefore on different acceleration scenarios.

astro-ph.HE↗

arXiv2022

Multiwavelength Analysis of Galactic Supernova Remnants

The origin of Galactic Cosmic Rays (CRs) and the possibility of Supernova Remnants (SNRs) being potential CR accelerators is still an open debate. The charged CRs can be detected indirectly by the {\gamma}-ray observatories through the {\pi^0} production and consequent decay, leading to the generation of high-energy {\gamma}-rays. The goal of the study is to identify qualitative and quantitative trends in favour of hadronic scenario and search for SNRs which could be potential accelerators up to PeV energies (PeVatrons). We have performed a Multiwavelength (MWL) study using different radiative models to evaluate the hadronic contribution. The spectral energy distributions (SEDs) of selected SNRs are modeled using the Naima [1] package. Two different radiative scenarios are considered, pure leptonic and lepto-hadronic scenarios, and different methods are used to evaluate their importance. This study shows that the lepto-hadronic scenario is favored for most SNRs. Two particular indicators of hadronic contribution come from the data around the {\pi^0} production threshold and the data above a few TeV. The hard rise at the {\pi^0} production threshold cannot be explained by leptonic processes. More data in this region would be valuable for these studies. For some SNRs, an important hadronic contribution is observed up to a few TeV, thus making them promising PeVatron candidates. In this high-energy region where the leptonic processes are expected to be suppressed, more data is required to help distinguish between the leptonic and hadronic origin of {\gamma}-ray emission. In the future, we intend to use the obtained model parameters to simulate data for CTA and assess its capability to identify PeVatrons.

astro-ph.HE↗