Letter to the Editor

Newborn jet in the symbiotic system R Aquarii

¹ Tartu Observatory, University of Tartu, Observatooriumi 1, Tõravere 61602, Estonia
² Physical Research Laboratory, Ahmedabad, Gujarat 380009, India
³ Observatorio Astronómico Nacional (OAN-IGN), Alfonso XII, 3, 28014 Madrid, Spain
⁴ NASA Ames Research Center, Moffett Field, CA 94035, USA
⁵ INAF National Institute of Astrophysics, Astronomical Observatory of Padova, 36012 Asiago (VI), Italy
⁶ MN Institute for Astrophysics, 116 Church Street, SE University of Minnesota, Minneapolis, MN 55455, USA
⁷ Astrophysics Research Centre, Lennard Jones Laboratories, Keele University, Keele, Staffordshire ST5 5BG, UK
⁸ NASA Exoplanet Science Institute, Caltech/IPAC, Mail Code 100-22, 1200 E. California Blvd., Pasadena, CA 91125, USA
⁹ Gemini Observatory/NSF’s NOIRLab, 670 N. A‘ohoku Place, Hilo, HI 96720, USA
¹⁰ The CHARA Array of Georgia State University, Mount Wilson Observatory, Mount Wilson, CA 91203, USA
¹¹ Earth and Space Exploration, Arizona State University, P.O. Box 876004 Tempe, AZ 85287-6004, USA

^★ Corresponding author: tiina.liimets@ut.ee

Received: 24 October 2025
Accepted: 17 November 2025

Abstract

Context. R Aquarii (R Aqr) is a well-known symbiotic binary that attracted renewed interest during its recent periastron passage, an event that occurs only once every ∼40 years. This passage marks the first to be observed with modern, state-of-the-art instruments.

Aims We investigated the inner, sub-arcsecond active region of R Aqr during this recent periastron passage, with the goal of gaining insight into the jet-launching mechanisms at work in this system.

Methods. We analysed Hα speckle interferometric images obtained one month apart using Fourier techniques. These are complemented by high-resolution optical spectra in the same emission line.

Results. Our speckle imaging reveals a newborn two-sided jet orientated in the north–south direction. Its proper motion, 66 ± 19 mas yr⁻¹, confirms that it was launched around 2020 January 7, at the onset of the periastron passage. Further analysis of the elongated central structure reveals a knot in the southern counterpart of the jet moving away from the binary with μ = 27 ± 17 mas yr⁻¹ at a position angle of 187° and an ejection time around 2019 October 28. This interpretation is further supported by our high-resolution spectroscopic data. In addition, we update the expansion parallax distance of R Aqr to 260 pc.