The spectroscopic orbit and the geometry of R Aqr

TL;DR

This study derives a reliable spectroscopic orbit for R Aqr, revealing an eccentric 43.6-year orbit and linking observed phenomena to orbital motion, enhancing understanding of this symbiotic binary system.

Contribution

The paper provides the first detailed spectroscopic orbit of R Aqr's Mira component and connects orbital dynamics with observed astrophysical phenomena.

Findings

Orbit has eccentricity e=0.25 with a period of 43.6 years.

Extinction increase in 1974-1981 linked to superior conjunction and obscuration.

Jet ejection appears unrelated to orbital position.

Abstract

R Aqr is one of the closest symbiotic binaries and the only D-type system with radial velocity data suitable for orbital parameters estimation. The aims of our study are to derive a reliable spectroscopic orbit of the Mira component, and to establish connections between the orbital motion and other phenomena shown by R Aqr. We reanalize velocity data recently published by McIntosh & Rustan complemented by additional velocities. We find an eccentric orbit (e=0.25) with a period 43.6 yr. This solution is in agreement with a resolved VLA observation of this system. We demonstrate that the last 1974-1981 increase of extinction towards the Mira occured during its superior spectroscopic conjunction, and can be due to obscuration by a neutral material in the accreting stream. We also show that jet ejection is not connected with the orbital position.