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The microquasar SS 433 is well-known for its precessing, relativisticbaryonic jets. Depending on their heating mechanism, the optical jet bulletsmay serve as a probe of the collimated radiation coming from the inner regionclose to the compact object. The optical interferometer VLTI/GRAVITY hasallowed to spatially resolved the optical jets in SS 433 for the first time. Wepresent here the second such observation taken over three nights in July 2017.In addition, we use the multi-wavelength XSHOOTER spectrograph at VLT to studythe optical bullets in SS 433 in detail. GRAVITY reveals elongatedexponential-like spatial profiles for the optical jets, suggestive of a heatingmechanism acting throughout a long portion of the jet and naturally explainedby photoionization by the collimated radiation. We also spatially resolve themovement of the optical bullets for the first time, detecting extended jetcomponents corresponding to previous ejections. \texttt{Cloudy} photoionizationmodels explain both the spatial intensity profiles measured with GRAVITY andthe line ratios from XSHOOTER, and constrain the properties of the opticalbullets and the ionizing radiation. We find that the latter must peak in the UVwith an isotropic luminosity (as inferred by a face on observer) $\approx10^{41}$ erg/s. Provided that the X-ray SED is sufficiently hard, thecollimated X-ray luminosity could still be high enough so that the face onobserver would see SS 433 as an ULX ($L_X \lesssim 10^{40}$ erg/s) and it wouldstill be compatible with the H/He/He+ ionization balance of the opticalbullets. The kinetic power in the optical jets is constrained to $3-20 \times10^{38}$ erg/s, and the extinction in the optical jets to $A_V = 6.7 \pm 0.1$.We suggest there may be substantial $A_V \gtrsim 1$ and structuredcircumstellar extinction in SS 433, likely arising from dust formed inequatorial outflows.

The Collimated Radiation in SS 433. Constraints from Spatially Resolved Optical Jets and $\texttt{Cloudy}$ Modeling of the Optical Bullets