A STUDY OF THE LUMINOUS BLUE VARIABLE CANDIDATE HE 3-519 AND ITS SURROUNDING NEBULA

He 3-519 is 20' away from the well-known LBV AG Car and is surrounded by a ring nebula 1' in diameter. In this paper, we present the first d etailed study of He 3-519 and its surrounding nebula based on high res olution spectra obtained at the AAT with the UCL echelle spectrograph for several epochs. The optical spectrum of He 3-519 is dominated by H I, He I and N II P Cygni profiles and contains weak He II lambda4686 emission. The SWP IUE spectrum consists mainly of Fe II absorption plu s a Si IV lambda1400 stellar wind feature. Two strong emission lines p ossibly due to Fe II and Fe III are present in the LWP spectrum. We fi nd that dramatic optical line profile variability is present in our sp ectra and comparison with earlier epochs back to 1989 shows that the B almer P Cygni absorption components disappear and reappear over timesc ales of weeks. We compare the spectral characteristics of He 3-519 wit h those of related stars and find that they are most similar to AG Car at, and just after, minimum. We further find that He 3-519 and AG Car at minimum have spectral features that are not consistent with a Ofpe /WN9 spectral type. We instead assign a new spectral class of WN11 to these two stars. We derive E(B-V)= 1.14 +/- 0.10 from the nebular line s, the strengths of diff-use interstellar bands and the 2200 angstrom feature. The measured nebular systemic velocity and the profiles of th e Na I and Ca II interstellar lines give a kinematic distance of 8.0 /- 1.0 kpc. The corresponding M(V) of He 3-519 is -7.1 +/- 0.6. We der ive various stellar parameters by fitting the He and H line profiles o f He 3-519 using the Hillier non-LTE model atmosphere code. We find T = 27 500 +/- 1000 K; log L/L. = 5.66(-0.19)+0.22, M = 1.3(-0.4)+0.8 1 0(-4) M. yr-1, upsilon(infinity) = 365 km s-1, and Y = 0.67 +/- 0.02. We also perform a similar analysis for AG Car and derive its parameter s at minimum in 1989 March. We find that both stars have lower tempera tures than WN7-8 stars but similar low hydrogen contents, in line with their new WN11 classifications. The position of He 3-519 on the HR di agram is just consistent with the upper luminosity/stability limit. Fi nally, we consider the nature of the nebula surrounding He 3-519. The shell shows deviations from spherical symmetry but overall is expandin g at 61 km s-1 and has an ionized mass of approximately 2 M.. The nebu lar parameters we derive and its similarity to the AG Car nebula indic ate that it was probably ejected from He 3-519 approximately 2 10(4) y r ago. The overall properties of He 3-519 and its nebula lead us to co nclude that it should be considered as a new LBV. Moreover, the evolve d status of both He 3-519 and AG Car indicate that they should properl y be considered as cool WN11 stars i.e. they are WR stars which are me mbers of the LBV class because of their proximity to the upper luminos ity boundary in the HR diagram. Similarly, their nebulae should be con sidered as examples of WR ring nebulae.