The Nebula Surrounding the B[e] Supergiant R4 release_qj7gw6cac5d4jjdawyogf2osi4

Abstract

<jats:title>Abstract</jats:title>New, NTT observations of the B[e] supergiant RMC4 in the Small Magellanic Cloud show that the star is embedded in a circumstellar nebula, whose velocity structure is typical of a bipolar outflow. The nebula is kinematically associated with RMC4 and expanding at 100 km/s on average. Its diameter as computed from the spatial extension of its spectral lines is of 8.6″ which corresponds to a linear size of 2.4 pc and gives a dynamical age of 12500 yr. The line ratio [NII]<jats:italic>λ</jats:italic>6584/[SII]<jats:italic>λ</jats:italic>6717 indicates that the nebula is nitrogen enriched as it is expected for ejected nebulae. This is the first bipolar outflow detected around a well-established B[e] supergiant which also belongs to a binary system. The nebular morphology and chemistry are consistent with the picture of a binary merger in which RMC4 was composed by a close pair and a third star (the observed companion). The close pair merged into a single star (the present B[e] supergiant) and produced a circumstellar nebula to be later shaped by the ensuing B star wind (cf. Langer &amp;amp; Heger 1998).
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