First high-resolution optical spectra of the distant emission-line star VES 723 (IRAS 02110+6212)

Abstract

The first high-resolution spectra (resolving powers of R ≥ 60 000) of the emission-line star VES 723, which has an unknown evolutionary status, were taken at the 6-m Big Telescope Alt-Azimuthal and the 3.6-m Canada-France-Hawaii Telescope. The spectrum is dominated with powerful emission lines of neutral hydrogen and helium, and forbidden singly ionized nitrogen. The Hα and He I lines were found to exhibit broad foundations of the emission profiles at least 250 km s^-1 wide. The strongest emission lines exhibit no noticeable variations during the observing period (2011-2017) except for the He I lines. The spectra contain multicomponent interstellar absorptions of Na I and K I (mult. 1) and several strongest diffuse interstellar bands, while photospheric absorptions have not been detected. The average radial velocity of the forbidden [N II] emission line centres was adopted as the systemic velocity (V_sys ≈ -52 km s^-1), which indicates a large distance of ≈6 kpc. Our luminosity estimates of log L/L_⊙ = 3.7-4.0 for two different Gaia distance measurements, along with an effective temperature of T_eff = 25 000 ± 2000 K and a fast decrease of the infrared flux longward of $\lambda \sim 10\, \mu{\rm m}$, allow us to suggest that VES 723 is neither a pre-main-sequence Herbig B[e] star nor a B[e] supergiant but rather a member of the FS CMa group of objects with the B[e] phenomenon.