Investigating the nature of MGRO J1908+06 with multiwavelength observations

Abstract

The unidentified TeV source MGRO J1908+06, with emission extending from hundreds of GeV to beyond 100TeV, is one of the most intriguing sources in the Galactic plane. MGRO J1908+06 spatially associates with an IceCube hotspot of neutrino emission. Although the hotspot is not significant yet, this suggests a possible hadronic origin of the observed gamma-ray radiation. Here we describe a multiwavelength analysis on MGRO J1908+06 to determine its nature. We identify, for the first time, an extended GeV source as the counterpart of MGRO J1908+06, discovering possibly associated molecular clouds (MCs). The GeV spectrum shows two well-differentiated components: a soft spectral component below $\sim 10$ GeV, and a hard one ($\Gamma \sim 1.6$) above these energies. The lower-energy part is likely associated with the dense MCs surrounding the supernova remnant SNR G40.5$-$0.5, whereas the higher-energy component, which connects smoothly with the spectrum observed in TeV range, resembles the inverse Compton emission observed in relic pulsar wind nebulae. This simple scenario seems to describe the data satisfactorily, but raises questions about the interpretation of the emission at hundreds of TeV. In this scenario, no detectable neutrino flux would be expected.

ApJL in press

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• Search for the Galactic accelerators of Cosmic-Rays up to the Knee with the Pevatron Test Statistic
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