Properties of Galactic B[e] Supergiants. V. 3 Pup–Constraining the Orbital Parameters and Modeling the Circumstellar Environments

Abstract

We report the results of long-term spectroscopic monitoring of the A-type supergiant with the B[e] phenomenon 3 Pup = HD 62623. We confirm earlier findings that it is a binary system. The orbital parameters were derived using cross-correlation of the spectra in a range of 4460–4632 Å, which contains over 30 absorption lines. The orbit was found to be circular with a period of 137.4 ± 0.1 days, radial velocity semiamplitude K 1  = 5.0 ± 0.8 km s −1 , systemic radial velocity γ  = +26.4 ± 2.0 km s −1 , and mass function M ⊙ . The object may have evolved from a pair with initial masses of ∼6.0 and ∼3.6 M ⊙ with an initial orbital period of ∼5 days. Based on the fundamental parameters of the A-supergiant (luminosity log L / L ⊙  = 4.1 ± 0.1 and effective temperature T eff  = 8500 ± 500 K) and evolutionary tracks of mass-transferring binaries, we found current masses of the gainer M 2  = 8.8 ± 0.5 M ⊙ and donor M 1  = 0.75 ± 0.25 M ⊙ . We also modeled the object’s IR-excess and derived a dust mass of ∼5  × 10 −5 M ⊙ in the optically thin dusty disk. The orbital parameters and properties of the H α line profile suggest that the circumstellar gaseous disk is predominantly circumbinary. The relatively low mass of the gainer led us to a suggestion that 3 Pup should be excluded from the B[e] supergiant group and moved to the FS CMa group. Overall these results further support our original suggestion that FS CMa objects are binary systems, where an earlier mass transfer caused formation of the circumstellar envelope.