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Description
Delta Cir is known as an O7.5 III eclipsing and spectroscopic binary with an eccentric orbit. Penny et al. discovered the presence of a third component in the IUE spectra. The eclipsing binary and the third body revolve around a common center of gravity with a period of 1644days in an eccentric orbit with a semimajor axis of 10AU. We demonstrate the presence of apsidal-line rotation with a period of {approx}141yr, which is considerably longer than its theoretically predicted value, based on the published radii of the binary components derived from the Hipparchos H_p_ light curve. However, our new solution of the same light curve resulted in smaller radii and better agreement between the observed and predicted period of the apsidal-line advance. There are indications that the third body is a binary. The object was resolved by VLTI using the PIONIER combiner; in 2012 June, the separation was 3.78mas with magnitude difference in the H region 1.75fm. This result means that (assuming a distance of 770pc) the inclination of the long orbit is 87.7{deg}.
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