Evidence of an Energetic Magnetar Powering 1LHAASO J0500$+$4454

Abstract

We investigate the origin of unidentified, extended TeV source 1LHAASO J0500$+$4454, considering three possible origins: cosmic rays interacting with a molecular cloud (MC), particles accelerated in a currently undetected supernova remnant (SNR), and an energetic outflow powered by a pulsar. Upper limits on the CO and X-ray emission from the $\gamma$-ray emitting region disfavor the MC and SNR scenarios, respectively. If a nebula of inverse Compton scattering $e^{\pm}$ powers 1LHAASO J0500$+$4454, then SED modeling indicates that the current particle energy in the nebula is $\sim 4 \times 10^{48}$ erg. If the coincident magnetar SGR 0501$+$4516's rotational energy powered 1LHAASO J0500$+$4454, then a conservative energy budget calculation requires an initial magnetar spin period $P_{0} \lesssim 5$ ms and a spin-down timescale $\tau_{\rm sd} \lesssim 30$ yr, which has implications for the origins of magnetars.