Astrophysical sources of very-high-energy (VHE) gamma-ray radiation provide unique information about astrophysical particle acceleration
and cosmic-ray production. In particular, compact binary systems, composed of a compact object (a neutron star or black hole) in orbit
with a massive stellar companion, provide an ideal environment for VHE gamma-ray production.
They are not only powerful particle accelerators, but they also exhibit periodic emission that makes them excellent astrophysical laboratories.
However, only a handful of binary systems have ever been observed in VHE gamma rays.
Partly, this is because VHE gamma-ray binaries appear to be very rare, and part is due to observational bias.
Most instruments operating at TeV are pointed and must allocate time to observing many kinds of objects.
The High Altitude Water Cherenkov (HAWC) Observatory, on the other hand, has high uptime (duty cycle >95%)
and a wide field of view (2 sr), making it well-suited for observing transient and time-varying sources such as binaries.
HAWC is also currently the only detector that is sensitive to gamma-ray photons above 10 TeV. SS 433 is a known microquasar
that has two jets ("east" and "west") terminating in radio lobes of a surrounding supernova remnant, W 50.
The recent observation of SS 433 with HAWC marked the first direct evidence of gamma-ray emission from the jets of a microquasar.
Using HAWC data, we have measured a VHE flux of e1 in the east lobe and w1 in the west lobe with a combined
post-trial statistical significance of 5.4 sigma.