A Long‐Period Spectroscopic Binary in the O‐Star Multiple System HD 193322

Abstract

We present radial velocity measurements and a single-lined spectroscopic orbit for the bright Otype star, HD 193322A, which we show to be a 311 day binary system that has a distant third companion (detected by speckle interferometry) in a 31 yr orbit. We suggest that the speckle companion appears in the spectrum as a broad-lined component of early B type. We also present a spectrum of the visual companion, HD 193322B, which appears to be an unresolved, double-lined spectroscopic binary. Thus, HD 193322, the central object in the open cluster Collinder 419, is a multiple system that contains at least five stars (possibly seven if the C and D components are physical). Such systems may play a key role in the dynamical ejection of runaway stars from young clusters.

An Interferometric and Spectroscopic Analysis of the Multiple Star System Hd 193322

“…Nevertheless, the spectral properties of the components are sufficiently different in this case that we may attempt radial velocity measurements. The appearance of the optical spectrum is dominated by a narrow-lined component that corresponds to the primary star in the close orbit, Ab1 (McKibben et al 1998). The secondary in the close orbit, Ab2, is fainter and contributes little to the composite spectrum ( §5).…”

“…The results are presented in Table 5 that lists the heliocentric Julian date of midexposure, the corresponding orbital phases in the close and wide systems (see below), the measured radial velocity and its associated error, a correction term for line blending effects, the observed minus calculated velocity residual from the fit (see below), and the observation source number from Table 4. Note that for completeness we have included in Table 5 velocities published earlier by McKibben et al (1998; indicated by a 0 in the final column).…”

“…1). Although component B may be a spectroscopic binary with a low semiamplitude (McKibben et al 1998), we simply assumed that it was stationary and contributed 11% of the total flux (Roberts et al 2010) in the next iteration of tomographic reconstruction. The power of the tomography algorithm to derive reliable and high quality reconstructed spectra increases with the number of spectra and with the orbital velocity range and flux contribution of the components.…”

“…The composite optical spectrum is dominated by a relatively narrow-lined component Ab1, and Fullerton (1990) discovered significant radial variations in this component indicative of a spectroscopic binary. The first spectroscopic orbit for Ab1 was presented by McKibben et al (1998), who determined an orbital period of 311 d. In addition to the close Ab1,Ab2 spectroscopic pair and the speckle Aa,Ab pair, there is another wider companion B at an angular separation of 2.68 arcsec (Turner et al 2008). Components C and D are more distant companions that also occupy the central region of Collinder 419 (Roberts et al 2010), and it is uncertain whether they are orbitally bound to the central multiple system.…”

The High Angular Resolution Multiplicity of Massive Stars

“…The preliminary 31 y orbit (Hartkopf et al 1993) had very small residuals but under sampled phase space (covering only 9% of the orbit). Subsequent to this, the A component was recognized as a close 311 d spectroscopic binary (McKibben et al 1998). In addition to the speckle resolution listed in Table 2, separated fringe packet solutions with the CHARA Array have been obtained several times since 2005.…”