Physical modelling of the circumstellar material in the early-type active binary HH Carinae

Abstract

ABSTRACT High-resolution spectra ($R\sim 48\, 000$) of the massive binary system HH Carinae have been analysed. Precise absolute parameters were derived from a simultaneous solution of the radial velocities and the light curves. The primary component is found to be an O9-type main-sequence star with a temperature of 33 500 K, while the secondary component is a B0-type giant/subgiant star with a temperature of 27 500 K. An analysis of the spectroscopic and photometric data has shown that the primary component rotates at a speed of vrot1 = 220 km s−1, which is three times faster than the synchronous rotation, while the secondary component synchronously rotates with the orbit at a speed of vrot2 = 150 km s−1. The distance to the system and the velocity of the centre of mass are determined as d = 4.6 ± 0.8 kpc and Vγ = –16 km s−1, respectively. The distance of the system is in agreement with the most probable Gaia distance of $4.9^{+0.9}_{-0.7}$ kpc and the distance in the latest data release (DR3) of 4.4 ± 0.3. Emission structures at the Hα region were modelled using the code shellspec where the derived absolute parameters of the components have been considered. Because the components are massive stars, mass loss as a result of stellar winds is expected. Produced models confirm that the components do indeed have strong stellar winds and there is mass transfer from the secondary to the primary. Stellar winds and the gas stream between the components have been modelled as a hot shell around the system, with a temperature of ∼22 000 K. Models also indicate that the interaction between the wind and the gas stream causes the formation of a high-temperature (100 000 K) impact region.