We present a quantitative analysis of the low-resolution ( \sim 4.5 Å ) spectra of 12 late-B and early-A blue supergiants ( BSGs ) in the metal-poor dwarf galaxy NGC 3109 .
A modified method of analysis is presented which does not require use of the Balmer jump as an independent T _ { eff } indicator , as used in previous studies .
We determine stellar effective temperatures , gravities , metallicities , reddening , and luminosities , and combine our sample with the early-B type BSGs analyzed by to derive the distance to NGC 3109 using the Flux-weighted Gravity-Luminosity Relation ( FGLR ) .
Using primarily Fe-group elements , we find an average metallicity of [ Z̄ ] = -0.67 \pm 0.13 , and no evidence of a metallicity gradient in the galaxy .
Our metallicities are higher than those found by based on the oxygen abundances of early-B supergiants ( [ Z̄ ] = - 0.93 \pm 0.07 ) , suggesting a low \alpha /Fe ratio for the galaxy .
We adjust the position of NGC 3109 on the BSG-determined galaxy mass-metallicity relation accordingly and compare it to metallicity studies of HII regions in star-forming galaxies .
We derive an FGLR distance modulus of 25.55 \pm 0.09 ( 1.27 Mpc ) that compares well with Cepheid and tip of the red giant branch ( TRGB ) distances .
The FGLR itself is consistent with those found in other galaxies , demonstrating the reliability of this method as a measure of extragalactic distances .