Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, no. 69, p. 45-52 (2024)
NON-THERMAL EMISSION OF SUPERNOVA REMNANTS AND PULSAR-WIND NEBULAE FROM THE MAGNETAR SGR1900+14 REGION
Anastasiia SOKAREVA, student
Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
Bohdan HNATYK, DSc (Phys. & Math.), Prof.
Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
Abstract
Introduction. High-energy processes in the interstellar medium (ISM) of our Galaxy are accompanied by the acceleration of a small fraction of nuclei and electrons to ultra-relativistic velocities. Accelerated particles – cosmic rays – generate non-thermal radiation. In particular, electrons – synchrotron and inverse Compton radiation (leptonic mechanism), protons and heavier nuclei – high-energy gamma-ray emission as a result of inelastic collisions with ISM atoms, in which, in particular, pions are born and quickly decay into two gamma-photons (hadronic mechanism). Supernova remnants and pulsar-wind nebulae are potential accelerators of Galactic cosmic rays. The work simulates the gamma-ray emission of the unidentified extended gamma-ray source 4FGL J1908.6+0915e within the framework of hadronic and leptonic mechanisms working in the Supernova remnants G42.8+0.6, G043.023+0.762, G043.070+0.558 and their pulsar-wind nebulae, which positionally coincide with the source 4FGL J1908.6+0915e on the sky map.
Methods. In order to model the non-thermal radiation (from the radio to the gamma-ray range) of the source 4FGL J1908.6+0915e, the observed spectrum of gamma-ray emission obtained by space-based (Fermi-LAT) and ground-based (H.E.S.S., HAWC) gamma-ray telescopes was approximated by a power-law with exponential cut-off. The NAIMA software code (Zabalza, 2016) was used for calculation the model spectra. The characteristics of potential sources of gamma-ray emission – of the Supernova remnants G42.8+0.6, G043.023+0.762 and G043.070+0.558 – were determined from the correspondence of the model spectra to the approximation of the observed spectrum.
Results. It is shown that the observed gamma-ray spectral flux of the source 4FGL J1908.6+0915e can be provided by each of the Supernova remnants G42.8+0.6, G043.023+0.762 and G043.070+0.558 or as a sum of their contributions. At the same time, due to the relative proximity of these remnants to the Earth (3-5 kpc), the required energy of the explosion of these Supernovae corresponds to the typical energy of Galactic Supernovae – about 1051 ergs.
Conclusions The unidentified extended source 4FGL J1908.6+0915e coincides in the sky position with the the magnetar SGR1900+14. In the work of Hnatyk et al. (2022) it is shown that it can be a manifestation of a Supernova remnant or a magnetar-wind nebula associated with a magnetar. But the necessary energies of the Supernova associated with the birth of the magnetar turn out to be extremely large – on the order of 1052 ergs due to the large distance to the magnetar – about 12.5 kpc. Such Supernovae – they are called Hypernovae – are rare phenomena in the Galaxy. In this paper, we have shown that other Supernova remnants G42.8+0.6, G043.023+0.762 and G043.070+0.558, which also coincide with the source 4FGL J1908.6+0915e on the sky map, but are at closer distances – 3-5 kpc – can provide the observed spectral flux already at typical energies of Supernova remnants – about 1051 ergs.
Key words
cosmic rays, Supernova remnants, pulsars, magnetars, pulsar-wind nebulae, non-thermal radiation.
References
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