Masses and radii of the components of 1016 Ori

Abstract

On January 2/3, 2001, eight spectra of the star V 1016 Ori were taken with the 2.6-m Crimean Astrophysical Observatory telescope on the descending branch of its eclipse. The spectral range λλ5299–5365 ÅÅ was chosen to be without strong lines of the primary B0 star, emission lines of the Orion Nebula, and telluric lines. Adding up the spectra and optimum filtering yielded a signal-to-noise (S/N) ratio of ∼600. We managed to identify thirteen lines of an A star that belong to the secondary component and seven lines of an M star that presumably belong to θ¹ Ori B1 (third star); the latter lies $0\mathop .\limits^{''} 2$ north of the binary system and was discovered by speckle interferometry. One of the lines is in emission. The radial velocities of both stars were measured. We calculated the components’ mass ratio, q=0.19. We also determined the semiamplitude of the secondary’s radial-velocity curve, K ^a=172 km s⁻¹, the components’ masses, M ^a = 21M _⊙ and M ^b = 3.9M _⊙, and radii, R ^a = 3.7R _⊙ and R ^b = 3.6R _⊙. The measured radial velocity V ^c_r =33 km s⁻¹ of θ¹ Ori B1 matches the binary’s γ velocity, within the error limits, which argues for the assumption that θ¹ Ori B1 is physically associated with the eclipsing system. The superscripts a, b, and c imply that a quantity belongs to the primary star, the secondary star, and θ¹ Ori B1, respectively. We estimated an upper limit on the projected rotational velocity for the secondary component and the third star, Vsini < 30 km s⁻¹.