Unveiling the nature of the unidentified gamma-ray sources 4FGL J1908.6+0915e, HESS J1907+089/HOTS J1907+091, and 3HWC J1907+085 in the sky region of the magnetar SGR 1900+14

TL;DR

This study explores the origins of gamma-ray emissions near the magnetar SGR 1900+14, suggesting they may arise from supernova remnants, pulsar wind nebulae, or star-forming regions, with implications for cosmic ray acceleration.

Contribution

It provides the first detailed simulation of gamma-ray emission from multiple potential sources around SGR 1900+14, considering both hadronic and leptonic models, and assesses their energy requirements.

Findings

Gamma-ray emission can include contributions from multiple source types.

Magnetar-connected SNRs and PWNe are promising but require large energy reserves.

Energy supply from magnetar hypernovae can explain observed emissions.

Abstract

Supernova remnants (SNRs), star formation regions (SFRs), and pulsar wind nebulae (PWNe) are prime candidates for Galactic PeVatrons. The nonthermal high-energy (HE, $\varepsilon>100 \textrm{ MeV}$) and very high-energy (VHE, $\varepsilon>100 \textrm{ GeV}$) $\gamma$-ray emission from these sources should be a promising manifestation of acceleration processes. We investigate the possibility to explain the HE and VHE $\gamma$-ray emission from the sky region of the magnetar SGR 1900+14 as a signature of cosmic rays accelerated in above mentioned sources. To this end, we simulate the $\gamma$-ray emission from the extended Fermi-LAT HE source 4FGL J1908.6+0915e, the extended VHE H.E.S.S. source candidate HOTS J1907+091, and the point-like HAWC TeV source 3HWC J1907+085, which are spatially coincident with the SNR G42.8+0.6, the magnetar SGR 1900+14 and the star forming region W49A. The simulations are performed within the hadronic and leptonic models. We show that the observed $\gamma$-ray emission from the region of the magnetar SGR 1900+14 can, in principle, include contributions of different intensities from all three types of (potentially confused) sources. The considered in detail cases of a magnetar-connected but still undetected SNR and a PWN are the most promising ones, but with a serious requirement on the energy reserve of radiated CR particles - of order of $10^{51}d_{\textrm{10kpc}}^{2}$ erg for sources at a distance of $d\sim 10$ kpc. Such energy reserve can be provided by the magnetar-related Hypernova and/or magnetar wind nebula remnant created by the newborn millisecond magnetar with the large supply of rotational energy $E_{\textrm{rot}}\sim 10^{52}\textrm{ erg}$.