V346 Centauri: Early-type eclipsing binary with apsidal motion and abrupt change of orbital period

Abstract

New physical elements of the early B-type eclipsing binary V346 Cen are derived using the HARPS spectra downloaded from the ESO archive and also numerous photometric observations from various sources. A model of the observed times of primary and secondary minima that fits them best is a combination of the apsidal motion and an abrupt decrease in the orbital period from 6 d .322123 to 6 d .321843 (shortening by 24 s), which occurred somewhere around JD 2 439 000. Assumption of a secularly decreasing orbital period provides a significantly worse fit. Local times of minima and the final solution of the light curve were obtained with the program PHOEBE. Radial velocities of both binary components, free of line blending, were derived via 2D cross-correlation with a program built on the principles of the program TODCOR. The oxygen lines in the secondary spectra are weaker than those in the model spectra of solar chemical composition. Using the component spectra disentangled with the program KOREL, we find that both components rotate considerably faster than would correspond to the synchronization at periastron. The apside rotation known from earlier studies is confirmed and compared to the theoretical value.

High-mass eclipsing binaries: A testbed for models of interior structure and evolution

“…Our HARPS spectra have good phase coverage and SPD quickly converged to a stable solution (Table 2). Our results are in reasonable agreement with the only previous spectroscopic analysis of this system (Mayer et al 2016), as expected because they used the same spectra.…”

“…However, the velocity amplitudes we measured are both 1.5 km s −1 lower than those of Mayer et al (2016). We attribute this to differences in the methods employed in the two analyses.…”

“…High-quality light curves in the Strömgren uvby system were obtained and analysed by the Copenhagen group (Giménez et al 1986a,b). The only full spectroscopic dataset for this system is our own HARPS data, available through the ESO archive, and which were already analysed by Mayer et al (2016).…”

“…We attribute this to differences in the methods employed in the two analyses. In particular, Mayer et al (2016) employed cross-correlation (Zucker & Mazeh 1994) to determine RVs, using as templates the disentangled spectra themselves. This approach is mathematically incorrect and extensive numerical experiments have shown that it is not reliable (Ilijic et al 2001); SPD has instead been shown to be the best approach to determining spectroscopic orbits (Southworth & Clausen 2007).…”

Investigating the lack of main-sequence companions to massive Be stars

“…They report an orbital period of 1.46 days while the shape and depth of the eclipses imply a companion of similar temperature and size. Mayer et al (2016) argue, based on the lack of RV variations in their spectra, that the lightcurve could also show typical Be star variability rather than show the signature of an eclipsing binary. The two archival FEROS spectra spectra are taken close to phase 0 so that no additional information about the binary status can be drawn from them.…”