was suggested long before the bubbles’ discovery, and models of “biconical hypershells” expanding away from the Galactic center can reproduce the X-ray and radio morphologies of the NPS [@sofue77; @sofue00; @sofue_etal16]. Alternatively, models of stellar winds and supernova remnants from the Sco–Cen OB association can also reproduce the X-ray and radio morphologies, in which case the emission occurs $\approx$200 pc away from the Sun [@egger_aschenbach95; @wolleben07]. In this scenario, the NPS has no affiliation from the Fermi bubbles, so analyzing its emission would lead to inaccurate measured bubble properties.

In light of these uncertainties, we choose to exclude observations that are projected through the NPS in our model fitting analysis. This is a conservative approach that prevents us from fitting hot gas emission that may be unrelated to our emission model. Furthermore, the NPS appears to be a unique feature in terms of its location on the sky. There should be similarly enhanced X-ray-emitting regions in the other quadrants of the sky if the NPS were due to the Fermi bubbles, but these are not seen in the *ROSAT* maps. Thus, modeling the NPS emission could lead to biased and inaccurate results.

We exclude observations near the NPS in two 