We present the results of high S/N long-slit spectroscopy with the Multiple Mirror and the SAO 6-m telescopes , optical imaging with the Wise 1-m telescope and H i observations with the Nançay Radio Telescope of the very metal-deficient ( 12+ \log ( O/H ) =7.64 ) luminous ( M _ { B } =–18 \aas@@fstack { m } 1 ) blue compact galaxy ( BCG ) HS 0837+4717 .
The blue bump near \lambda 4650 , characteristic of WR stars is detected in the central supergiant H ii region , as well as the barely seen red bump at \lambda 5808 .
The derived number of WR stars in the region of the current starburst is \sim 1000 .
Evidence for fast motions in this region is also seen as broad , low-contrast components in the H \alpha , H \beta and strong [ O iii ] lines \lambda \lambda 4959,5007 .
While the extinction of the narrow emission lines from the supergiant H ii region is low , the very large Balmer decrement of the broad components suggests that the part of current starburst is highly obscured by dust .
Abundance ratios X/O for X=Ne , Ar , S , Fe and Cl in the supergiant H ii 
region are in good agreement with the mean values of other very metal-deficient BCGs .
Nitrogen , however , is overabundant by a factor of \sim 6 .
This implies an unusually efficient N enrichment in HS 0837+4717 , and probably , a non-typical evolution scenario .
The H \alpha -line Position–Velocity ( P–V ) diagrams for directions approximately along the major and minor axes reveal disturbed motions of the ionized gas , mainly in peripheral regions .
The SW part of the major axis P–V diagram looks like a rotation curve , with the velocity amplitude V _ { rot } \sim 50–70 km s ^ { -1 } at r =4.3 kpc .
Its NE part displays , however , strong deviations , indicating either counter-rotation , or a strong outflow/supershell .
If it is considered as indicating a shell-like feature its velocity amplitude of \sim 70 km s ^ { -1 } ( relative to the extrapolated rotation curve ) , and the apparent extent of \sim 4″ ( 3.3 kpc ) imply a dynamical age of \sim 14 Myr and the full energetic equivalent of \sim 2.3 \times 10 ^ { 4 } SNe .
The latter indicates continuing starbursts during at least this time interval .
The long-slit spectra reveal a complex morphology for this galaxy .
It consists of two compact regions at a distance of \sim 2 kpc .
Their continuum flux differs by a factor of four .
The brightest one is related to the current starburst with the age of \sim 3.7 Myr .
The slightly redder fainter component could be an older starburst ( \sim 25 Myr ) .
The Wise 1-m telescope UBVR integrated photometry reveals a high optical luminosity for this BCG , and the unusual ( B - V ) 
and ( V - R ) colours .
The morphology of HS 0837+4717 is highly disturbed , with two small tails emerging to NNW and SSE .
Such a disturbed overall morphology , a ” double-nucleus ” structure , significantly disturbed velocities of ionized gas , together with the very high power of the starburst suggests a possible explanation of the object as a recent merger .
We compare the properties of this BCG and of similar objects known in the literature , and conclude that their high nitrogen excess is most probably related to the short phase of a powerful starburst when many WR stars contribute to the enrichment of ISM .