The multiple star systems V454 Car and HX Vel

Presented by Ed Budding, Mark Blackford, Roger Butland, (et al.)

We present combined photometric and spectroscopic analyses of the southern close binary systems V454 Car and HX Vel. High-resolution spectra of these systems were taken at the University of Canterbury Mt. John Observatory in the years 2009-15. Absolute parameters for the triple (at least) system V454 Car confirm its young and near-Main-Sequence nature. We find: M1 = 6.30+/-0.20, M2 = 5.86+/-0.18, R1 = 3.12+/-0.05, R2 = 3.04+/-0.04, (all in solar units); T1 ~19000, T2 ~18500 (K); photometric distance ~ 550 (pc).

The close binary is found to be the major component (A) of a multiple star, whose other main component (B) is also probably a binary. The two components are in eccentric orbits about a common centre of gravity with a period of ~ 1900 d. Analysis of the radial velocity curves is strongly suggestive that the mass of component B is greater than that of its visible member, while the measured radial velocities of this visible star show irregularities incompatible with reasonable measurement accuracies. These variations occur on a timescale of days to weeks. For HX Vel we find absolute parameters as follows: M1 = 9.6+/-0.4, M2 = 5.6+/-0.3, R1 = 4.80+/-0.18, R2 = 3.05+/-0.16, (all in solar units); T1 ~25000, T2 ~17000 (K); photometric distance ~ 390+/-30 (pc).

HX Vel, the brighter component of the visual pair CCDM J08423-4806 AB is often considered to be the brightest member of the cluster IC 2395. There appears to be an inconsistency in the distance estimates, however. The ~400 pc distance of our determination would make the system a likely member of the Sco-Cen OB2 Association within Gould’s Belt.