Paper detail

GeV-TeV Counterparts of SS 433/W50 from Fermi-LAT and HAWC Observations

The extended jets of the microquasar SS 433 have been observed in optical, radio, X-ray, and recently very-high-energy (VHE) $γ$-rays by HAWC. The detection of HAWC $γ$-rays with energies as great as 25 TeV motivates searches for high-energy $γ$-ray counterparts in the Fermi-LAT data in the 100 MeV--300 GeV band. In this paper, we report on the first-ever joint analysis of Fermi-LAT and HAWC observations to study the spectrum and location of $γ$-ray emission from SS~433. Our analysis finds common emission sites of GeV-to-TeV $γ$-rays inside the eastern and western lobes of SS 433. The total flux above 1 GeV is $\sim 1\times10^{-10}\,\rm cm^{-2}\,s^{-1}$ in both lobes. The $γ$-ray spectrum in the eastern lobe is consistent with inverse-Compton emission by an electron population that is accelerated by jets. To explain both the GeV and TeV flux, the electrons need to have a soft intrinsic energy spectrum, or undergo a quick cooling process due to synchrotron radiation in a magnetized environment.