An extended nebulosity surrounding the S Dor variable R 127

Abstract

Using the CASPEC echelle spectrograph of the European Southern Observatory, La Silla, Chile, we obtained new high resolution spectrograms of the LMC S Dor variable R 127 in the blue and red spectral range.

The red spectrogram, which contains the [N II] 6548 and 6533 and the [S II] 6717 and 6731 lines shows the presence of a well resolved extended gaseous nebula around R 127 (see Figures 1 and 2). The nebula (which is also detected at the Balmer lines) shows blueshifted and redshifted emission (projected) on the position of the stellar continuum, and no wavelength-shift at the maximum (East-West) distance from the star. Hence, the nebulosity appears to be an expanding shell, reminiscent of the nebula around the galactic extreme supergiant AG Car. The angular diameter (or East-West extension) of the nebula around R 127 is of the order 4“, corresponding to ≈1 pc at the distance of the LMC. The expansion velocity of the R 127 nebula is found to be 28 km s⁻¹ from our spectrograms. Hence, assuming a constant expansion velocity we derive a kinematic age of the R 127 nebula of ≈2 · 10⁴ years. This corresponds closely to the expected lifetime of the S Dor evolutionary phase.

A more detailed description of our results will be published in the proceedings of the Workshop on “Instabilities in Luminous Early Type Stars” (C. de Loore, H. Lamers, eds.) Lunteren 1986.