A quantitative study of the Luminous Blue Variable NGC 2363-V1 in the Magellanic galaxy NGC 2366 ( D = 3.44 Mpc ) is presented , based on ultraviolet and optical Hubble Space Telescope STIS spectroscopy .
Contemporary WFPC2 and William Herschel Telescope imaging reveals a modest V-band brightness increase of \sim 0.2 mag per year between 1996 January–1997 November , reaching V=17.4 mag , corresponding to M _ { V } = - 10.4 mag .
Subsequently , V1 underwent a similar decrease in V-band brightness , together with a UV brightening of 0.35 mag from 1997 November to 1999 November .

The optical spectrum of V1 is dominated by H emission lines , with Fe ii , He i and Na i also detected .
In the ultraviolet , a forest of Fe absorption features and numerous absorption lines typical of mid-B supergiants ( such as Si ii , Si iii , Si iv , C iii , C iv ) are observed .
From a spectral analysis with the non-LTE , line-blanketed code of Hillier & Miller ( 1998 ) , we derive stellar parameters of T _ { \ast } =11kK , R _ { \ast } =420 R _ { \odot } , log ( L / L _ { \odot } ) =6.35 during 1997 November , and T _ { \ast } =13kK , R _ { \ast } =315 R _ { \odot } , log ( L / L _ { \odot } ) =6.4 for 1999 July .
The wind properties of V1 are also exceptional , with \dot { M } \simeq 4.4 \times 10 ^ { -4 } M _ { \odot } yr ^ { -1 } and v _ { \infty } \simeq 300 km s ^ { -1 } , allowing for a clumped wind ( filling factor = 0.3 ) , and assuming H/He \sim 4 by number .

The presence of Fe lines in the UV and optical spectrum of V1 permits an estimate of the heavy elemental abundance of NGC 2363 from our spectral synthesis .
Although some deficiencies remain , allowance for charge exchange reactions in our calculations supports a SMC-like metallicity , that has previously been determined for NGC 2363 from nebular oxygen diagnostics .

Considering a variety of possible progenitor stars , V1 has definitely undergone a giant eruption , with a substantial increase in stellar luminosity , radius , and almost certainly mass-loss rate , such that its stellar radius increased at an average rate of \sim 4 km s ^ { -1 } during 1992 October – 1995 February .
The stellar properties of V1 are compared to other LBVs , including \eta Car and HD 5980 during its brief eruption in 1994 September , the latter newly analyzed here .
The mass-loss rate of the HD 5980 eruptor compares closely with V1 , but its bolometric luminosity was a factor \sim 6 times larger .