HD 152246 - a new high-mass triple system and its basic properties

TL;DR

This study reveals that HD 152246 is a hierarchical triple system with a close inner binary and a distant third component, providing detailed orbital and spectral properties through combined spectroscopic and interferometric analysis.

Contribution

First detailed orbital and spectral analysis of HD 152246 as a high-mass triple system using multi-epoch spectroscopy and interferometry, confirming its hierarchical structure and characterizing component properties.

Findings

HD 152246 is a hierarchical triple system with a 6-day inner orbit and a 470-day outer orbit.

Interferometry confirms the orbital parameters and provides stellar masses of approximately 20.4 and 22.8 solar masses.

Spectral disentangling suggests component A is an O9 IV star and component Ba is an O9 V star, with specific temperature and rotational velocity measurements.

Abstract

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.