1995A&A...293..363P

The A2 supergiant 3 Puppis is surrounded by circumstellar gas, as is attested by the double-peaked emission displayed by the Hα lines, the NaID lines and the lines of [OI]. In addition, a large infrared excess due to dust in a disk is observed. The presence of circumstellar dust around an A-supergiant is unusual, and has led to the suggestion that 3 Puppis is not a massive supergiant, but rather an evolved low-mass object in transition between the AGB-phase and the planetary nebula phase. However, the photometric and spectroscopic data provide convincing arguments to conclude that 3 Puppis is a genuine massive supergiant. The question arises which physical mechanism could yield this circumstellar matter. An important clue might be the binary nature of the star. The radial velocity of the star has been known to be variable since early this century. An orbital period of about 150 days is derived. This is fairly short for an A-type supergiant, so that it appears rather likely that the presence of circumstellar material is caused by non-conservative mass transfer in a binary system in which the primary nearly fills its Roche lobe. The resemblance of 3 Puppis with υ Sgr is discussed, and we conclude that it is unlikely that there is an evolutionary link between both objects. A result of more general interest is the realisation that the presence of a companion, even when it is much less massive than the primary, can drastically affect a stellar wind.