We present new , NTT longslit spectroscopy of the B [ e ] supergiant in the binary system R4 in the Small Magellanic Cloud .
The data show extended , forbidden N and S emissions which are typical signatures of circumstellar matter .
Their extension along the space axis of the slit defines an angular size of 8.6 ^ { \prime \prime } which translates into a linear size of 2.4 pc .
The N emission lines also show the velocity structure of a bipolar outflow expanding at 100 km s ^ { -1 } on average .
This implies that , for a measured radius of 1.2 pc , the outflow originated about 1.2 \times 10 ^ { 4 } yr ago .
The line flux ratio [ NII ] 6584/ [ SII ] 6717 indicates that the nebula is nitrogen enriched and therefore it has been ejected from the central star .

This is the first bipolar , ejection nebula detected around a well-established B [ e ] supergiant .
The bipolar morphology and the chemical enrichment shown by the nebula associated with R4 are consistent with the picture of a binary merger ( Langer & Heger 1998 ) , in which R4 was originally a system composed by a close pair and a third star ( the observed A companion ) .
The close pair merged into a single star and the merging process produced a circumstellar nebula that was later shaped by the ensueing B star wind .

Since the bipolar morphology , the kinematics and the enriched chemical composition make the nebula surrounding R4 very similar to the observed LBV nebulae , our findings imply that at least a few LBV outbursts and nebulae might well be the result of the merging process of two massive stars .