English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

In this work, we compare the $\gamma$-ray spectra available in literaturefrom 11 middle aged supernova remnants (SNRs) interacting with molecular clouds(MCs). It is found that 5 remnants prefer a smoothly broken power law protonspectrum with similar power law index but different break energy. The rest ofthe SNRs need updated data to test whether a spectral break is preferred in theproton spectrum. Then we compare the $\gamma$-ray spectra from all 11 SNRs withthe prediction from widely accepted escaping scenario and direct interactionscenario. We show that current $\gamma$-ray data is inconsistent with theescaping model statistically, as it predicts a diversity of $\gamma$-rayspectra which is not detected in the observation. We also find that ambient CRscan be very important for the $\gamma$-ray emission in the MCs external to W28and W44, which requires further investigation. In the direct interactionscenario, we focus on re-acceleration of pre-existing ambient CRs. The modelcan produce the overall profile of $\gamma$-ray data with differentacceleration time, but it suggests a transition of seed particles in theevolution of SNR. Whether such transition indeed exists has to be tested byfuture observation. In the end, we propose that radiative SNR without MCinteraction can also produce a significant amount of $\gamma$-ray emission. Onegood candidate is S147. With accumulated Fermi data and CTA in future we expectto detect more remnants like S147.

Similarity of $\gamma$-ray spectrum in middle aged supernova remnants (SNRs) interacting with molecular clouds (MC): what can we learn?