Abstract

Contributed Talk - Splinter PlanetFormation

Thursday, 18 September 2025, 17:30

Multiplicity and inner gas kinematics in the GU CMa system probed with VLTI/GRAVITY

A. Popovik, L. Labadie, K. Perraut, J. Sanchez-Bermudez, J. Bouvier, and the GRAVITY Collaboration
¹ I. Physikalisches Institut, University of Cologne, Germany ² Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France ³ Instituto de Astrofísica de Andalucía (IAA-CSIC), Granada, Spain

Protoplanetary disks are a key ingredient in planet formation, and multiplicity can have a strong impact on their lifetime and evolution. We studied the Herbig Be-classified multiple star GU CMa located in a cluster older than the active star-forming cluster Z CMa by a few Myr. We used long-baseline near-infrared interferometry with VLTI//GRAVITY to reach milliarcsecond resolution in the K-band to probe the innermost regions around the central spectroscopic binary of GU CMa located at approximately 600 pc. Through an analysis of the GRAVITY continuum data, we (re)discover that the central binary is actually a triple system, with a 4.8 solar mass companion orbiting at a separation of 20 au and with an extreme eccentricity of e = 0.97. Though we show the system is dynamically stable, its close multiple nature is probably responsible for the rapid clearing of the circumstellar disk(s). However, the presence of circumstellar disks is not clearly supported by our modeling, which could be in line with the non-detection of a clear near-IR excess. Furthermore, we analyzed the spatial and kinematic properties of the Br-gamma emission line by measuring the characteristic size and photocenter of the gas component. The Br-gamma emission is found to be spatially unresolved, with most Br-gamma emission located at the position of the spectroscopic binary and without detectable contribution at the location of the newly detected companion at 20 au. The kinematic profile is found to be more complex than a Keplerian disk and also time-variable across the epochs. We discuss whether, while often reported as a young Herbig Be star, GU CMa could in fact be a classical Be star.