2018ApJ...856..158K

We report the results of spectroscopic and photometric observations of the emission-line object AS 386. For the first time we found that it exhibits the B[e] phenomenon and fits the definition of an FS CMa type object. The optical spectrum shows the presence of a B-type star with the following properties: T_eff = 11,000 ± 500 K, log L/L_☉ = 3.7 ± 0.3, a mass of 7 ± 1 M_☉, and a distance D = 2.4 ± 0.3 kpc from the Sun. We detected regular radial velocity variations of both absorption and emission lines with the following orbital parameters: P_orb =131.27 ± 0.09 days, semiamplitude K₁ = 51.7 ± 3.0 km s^–1, systemic radial velocity γ = -31.8 ± 2.6 km s^–1, and a mass function of f(m) = 1.9 ± 0.3 M_☉. AS 386 exhibits irregular variations of the optical brightness (V = 10.92 ± 0.05 mag), while the near-IR brightness varies up to ∼0.3 mag following the spectroscopic period. We explain this behavior by a variable illumination of the dusty disk inner rim by the B-type component. Doppler tomography based on the orbital variations of emission-line profiles shows that the material is distributed near the B-type component and in a circumbinary disk. We conclude that the system has undergone a strong mass transfer that created the circumstellar material and increased the B-type component mass. The absence of any traces of a secondary component, whose mass should be >=7 M_☉, suggests that it is most likely a black hole.