| Title: |
Evidence for the Keplerian orbit of a close companion around a giant star |
| Authors: |
Esseldeurs, Mats; Decin, Leen; De Ridder, Joris; Mori, Yoshiya; Karakas, Amanda I.; Malfait, Jolien; Danilovich, Taíssa; Mathis, Stéphane; Richards, Anita M. S.; Sahai, Raghvendra; Yates, Jeremy; Van de Sande, Marie; Baes, Maarten; Baudry, Alain; Bolte, Jan; Ceulemans, Thomas; De Ceuster, Frederik; El Mellah, Ileyk; Etoka, Sandra; Gottlieb, Carl; Herpin, Fabrice; Kervella, Pierre; Landri, Camille; Marinho, Louise; McDonald, Iain; Menten, Karl; Millar, Tom; Osborn, Zara; Pimpanuwat, Bannawit; Plane, John; Price, Daniel J.; Siess, Lionel; Vermeulen, Owen; Wong, Ka Tat |
| Publication Year: |
2026 |
| Collection: |
The Open University: Open Research Online (ORO) |
| Description: |
Close companions influence stellar evolution through tidal interactions, mass transfer and mass-loss effects. While such companions are detected around young stellar objects, main-sequence stars, red giants and compact objects, direct observational evidence of close-in companions around asymptotic giant branch (AGB) stars has remained elusive. Here we present (sub)millimetre time-domain imaging spectroscopy revealing the Keplerian motion of a close-in companion around the AGB star π 1 Gruis. The companion, slightly more massive than the AGB star, is likely a main-sequence star. Unlike more evolved stars with companions at comparable distances, the companion of π 1 Gruis follows a circular orbit, suggesting an eccentricity-generating mechanism during the late- or post-AGB phase. Our analysis suggests that model-predicted circularization rates may be underestimated. Our results highlight the potential of multi-epoch (sub)millimetre interferometry in detecting the Keplerian motion of close companions to giant stars and open avenues for our understanding of tidal interaction physics and binary evolution. |
| Document Type: |
article in journal/newspaper |
| File Description: |
application/pdf |
| Language: |
English |
| Relation: |
https://oro.open.ac.uk/107373/1/Accepted%20paper%20final%20JMCP.pdf; Esseldeurs, Mats; Decin, Leen; De Ridder, Joris; Mori, Yoshiya; Karakas, Amanda I.; Malfait, Jolien; Danilovich, Taíssa; Mathis, Stéphane; Richards, Anita M. S.; Sahai, Raghvendra; Yates, Jeremy; Van de Sande, Marie; Baes, Maarten; Baudry, Alain; Bolte, Jan; Ceulemans, Thomas; De Ceuster, Frederik; El Mellah, Ileyk; Etoka, Sandra; Gottlieb, Carl; Herpin, Fabrice; Kervella, Pierre; Landri, Camille; Marinho, Louise; McDonald, Iain ; Menten, Karl; Millar, Tom; Osborn, Zara; Pimpanuwat, Bannawit; Plane, John; Price, Daniel J.; Siess, Lionel; Vermeulen, Owen and Wong, Ka Tat (2026). Evidence for the Keplerian orbit of a close companion around a giant star. Nature Astronomy, 10 pp. 124–143. |
| Availability: |
https://oro.open.ac.uk/107373/; https://oro.open.ac.uk/107373/1/Accepted%20paper%20final%20JMCP.pdf |
| Rights: |
cc_by_nc_nd_4 |
| Accession Number: |
edsbas.42241705 |
| Database: |
BASE |