Analyses of multi-epoch, high-resolution (R ~ 50.000) optical spectra of the
O-type star HD 152246 (O9 IV according to the most recent classification),
complemented by a limited number of earlier published radial velocities, led to
the finding that the object is a hierarchical triple system, where a close
inner pair (Ba-Bb) with a slightly eccentric orbit (e = 0.11) and a period of
6.0049 days revolves in a 470-day highly eccentric orbit (e = 0.865) with
another massive and brighter component A. The mass ratio of the inner system
must be low since we were unable to find any traces of the secondary spectrum.
The mass ratio A/(Ba+Bb) is 0.89. The outer system has recently been resolved
using long-baseline interferometry on three occasions. The interferometry
confirms the spectroscopic results and specifies elements of the system. Our
orbital solutions, including the combined radial-velocity and interferometric
solution indicate an orbital inclination of the outer orbit of 112{\deg} and
stellar masses of 20.4 and 22.8 solar masses. We also disentangled the spectra
of components A and Ba and compare them to synthetic spectra from two
independent programmes, TLUSTY and FASTWIND. In either case, the fit was not
satisfactory and we postpone a better determination of the system properties
for a future study, after obtaining observations during the periastron passage
of the outer orbit (the nearest chance being March 2015). For the moment, we
can only conclude that component A is an O9 IV star with v*sin(i) = 210 +\- 10
km/s and effective temperature of 33000 +\- 500 K, while component Ba is an O9
V object with v*sin(i) = 65 +/- 3 km/s and T_eff = 33600 +\- 600 K.Comment: 9 pages, 6 figures, accepted for publication in Astronomy and
Astrophysic
