We report near-infrared photometry , spectroscopy , and speckle imaging of the hot , luminous star we identify as candidate LBV 1806-20 We note that this star has not been observed to undergo a major LBV outburst yet , and thus some may not consider it to be an LBV ( though it is undoubtedly luminous , blue , and variable , and shares many spectral characteristics with bone fide LBV stars , as we show here ) .
Hereafter , to avoid awkward phrasing , we refer to the candidate LBV as LBV 1806-20 as is done in the literature . .
We also present photometry and spectroscopy of 3 nearby stars , which are members of the same star cluster containing LBV 1806-20 and SGR 1806-20 .
The spectroscopy and photometry show that LBV 1806-20 is similar in many respects to the luminous “ Pistol Star ” , albeit with some important differences .
They also provide estimates of the effective temperature and reddening of LBV 1806-20 , and confirm distance estimates , leading to a best estimate for the luminosity of this star of > 5 \times 10 ^ { 6 } L _ { \odot } .
The nearby cluster stars have spectral types and inferred absolute magnitudes which confirm the distance ( and thus luminosity ) estimate for LBV 1806-20 .
If we drop kinematic measurements of the distance ( 15.1 ^ { +1.8 } _ { -1.3 } kpc ) , we have a lower limit on the distance of > 9.5 
kpc , and on the luminosity of > 2 \times 10 ^ { 6 } L _ { \odot } , based on the cluster stars .
If we drop both the kinematic and cluster star indicators for distance , an ammonia absorption feature sets yet another lower limit to the distance of > 5.7 kpc , with a corresponding luminosity estimate of > 7 \times 10 ^ { 5 } L _ { \odot } for the candidate LBV 1806-20 .
Furthermore , based on very high angular-resolution speckle images , we determine that LBV 1806-20 is not a cluster of stars , but is rather a single star or binary system .
Simple arguments based on the Eddington luminosity lead to an estimate of the total mass of LBV 1806-20 ( single or binary ) exceeding 190 M _ { \odot } .
We discuss the possible uncertainties in these results , and their implications for the star formation history of this cluster .