Letter to the Editor

A companion in V1247 Ori supported by motion in the pattern of the spiral arm^⋆,⋆⋆

¹ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
e-mail: bin.ren@oca.eu
² Université Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique (IPAG), 38000 Grenoble, France
³ Department of Physics and Astronomy, The Johns Hopkins University, 3701 San Martin Drive, Baltimore, MD 21218, USA
⁴ Aix Marseille Univ., CNRS, CNES, LAM, Marseille, France
e-mail: chen.xie@lam.fr
⁵ Department of Physics & Astronomy, University of Victoria, Victoria, BC V8P 5C2, Canada
⁶ Department of Astronomy, University of Florida, Gainesville, FL 32611, USA
⁷ Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
⁸ European Southern Observatory, Alonso de Córdova 3107, Vitacura Casilla, 19001 Santiago, Chile
⁹ AURA, for ESA, Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA
¹⁰ INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
¹¹ School of Natural Sciences, University of Galway, University Road, H91 TK33 Galway, UK
¹² Astrophysics Group, Department of Physics & Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK

Received: 29 September 2023
Accepted: 6 December 2023

Abstract

While nearly two dozen spiral arms have been detected from planet-forming disks in near-infrared scattered light, none of their substellar drivers has been confirmed. By observing spiral systems in at least two epochs spanning multiple years and measuring the motion of the spirals, we can distinguish what causes the spirals and locate the orbits of the driving planets if the spirals are triggered by them. Upon a recent validation of this approach using the comotion between a stellar companion and a spiral, we obtained a second-epoch observation for the spiral system in the disk of V1247 Ori in the H-band polarized scattered light using Very Large Telescope (VLT), SPHERE, and IRDIS. By combining our observations with archival IRDIS data, we established a 4.8 yr timeline to constrain the spiral motion of V1247 Ori. We obtained a pattern speed of 0°.40 ± 0°.10 yr⁻¹ for the northeast spiral. This corresponds to an orbital period of 900 ± 220 yr, and the semimajor axis of the hidden planetary driver therefore is 118 ± 20 au for a 2.0 ± 0.1 M_⊙ central star. The location agrees with the gap in ALMA dust-continuum observations, which provides joint support for the hypothesis that a companion drives the scattered-light spirals while carving a millimeter gap. With an angular separation of 0″​​.29 ± 0″​​.05, this hidden companion is an ideal target for JWST imaging.