http://arxiv.org/abs/2112.04875
Context. Fermi Large Area Telescope (LAT) data and analysis tools improved a lot after the last analysis on Kes 79 (Auchettl et al. 2014) whose age is 4.4-6.7 kyr. Recent multi-wavelength studies on this mid-aged supernova remnant (SNR) revealed more physical properties of it, e.g., the age, the size, the shock-cloud interaction.
Aims. In this work, we analyse the 11.5-year Fermi-LAT data to investigate the -ray features in this region. Then, we explore several models to infer their origins.
Methods. We use the >5 GeV Fermi-LAT data to better distinguish sub-features in the SNR region, and then extend the energy down to 100 MeV to investigate the spectrum of the entire SNR region. We explored hadronic models with leaked cosmic-rays (CRs) from the shock-cloud collision, and also examine the leptonic contribution from pulsars in/around this region.
Results. In our work, our result shows a more significant detection ($\sim$34.8$\sigma$) with 4FGL J1852.4+0037e. And it also shows a low peak energy E$_{break} \sim $ 0.5 GeV with the spectrum down to 100 MeV with BPL model fit. In $\ge$5 GeV, we detect two extend sources, Src-N located to the north of the SNR and Src-S to the south of the SNR. They have different spectral shapes.
Conclusions. Our hadronic model with leaked CRs from the SNR Kes 79 after the shock-cloud collision can predominantly reproduce the GeV emission at a northeast part of Src-S with typical values of parameters. Three known pulsars inside Src-S release a total power that is too low to account for the $\gamma$-ray emission. On the other hand, we found that the SNR cannot provide enough CRs reaching clouds at Src-N to explain the local GeV spectrum, and we propose that the Src-N emission may be dominated by a putative pulsar-wind-nebula powered by PSR J1853+0056.
X. He, Y. Cui, P. Yeung, et. al.
Fri, 10 Dec 21
48/94
Comments: Submitted to A&A on 08.12.2021