We report the analysis of optical spectra of the extreme helium star LSS 3184 ( BX Cir ) to determine its effective temperature and gravity throughout its pulsation cycle .
The spectra were also used to measure its chemical abundances .

We report rest gravity , \log g = 3.38 \pm 0.02 , and a chemical abundance mixture consistent with those reported earlier in a study using an optical spectrum with lower spectral resolution and a lower signal to noise ratio .
Our analysis decreases the upper limit for the H abundance to { H < 6.0 } ( mass fraction < 7.1 \times 10 ^ { -7 } ) .
Our gravity corresponds to stellar mass M = 0.47 \pm 0.03 M _ { \odot } .

We find that the effective \log g varies through the pulsation cycle with an amplitude of 0.28 dex .
The effective gravity is smaller than the rest gravity except when the star is very near its minimum radius .
The change in effective gravity is primarily caused by acceleration of the stellar surface .

Based on the optical spectra , we find the temperature varies with an amplitude of 3450 K. We find a time averaged mean temperature , 23390 \pm 90 K , consistent with that found in the earlier optical spectrum study .
The mean temperature is 1750 K hotter than that found using combined ultraviolet spectra and V and R photometry and the variation amplitude is larger .
This discrepancy is similar to that found for the extreme helium star V652~Her .