Abstract

Contributed Talk - Splinter PlanetFormation

Thursday, 18 September 2025, 16:50

Unveiling the Inner Architecture of the β Pictoris System with GRAVITY+: Disk Alignment and Signs of a Potential Inner Disk

Jonas Sauter, Wolfgang Brandner
Max-Planck-Institut für Astonomie

The β Pictoris system, home to two debris disks and two giant planets, is one of the most iconic directly imaged planetary systems. Yet, despite decades of study, fundamental questions remain: is the star’s spin axis truly aligned with its multi-component disk, and what role do the infalling, evaporating bodies play in shaping the system’s present-day architecture? These are more than details — the degree of alignment offers direct clues to the system’s birth environment, revealing whether its planets and disks formed in a calm, co-planar configuration or were later sculpted by violent dynamical events such as planetary migration. To address these questions, we used a full night of GRAVITY+ observations, alternating between the star and planet β Pic b, in four-UT high spectral resolution (R ≈ 4000) mode. GRAVITY+, the major upgrade to the four-telescope Very Large Telescope Interferometer, combines improved throughput with extreme angular resolution (λ/B ≈ 1 mas). This enabled astrospectroscopy of the Br γ line with microarcsecond astrometric precision, and high-fidelity visibilities and closure phases thanks to brought uv-coverage. We resolve the inner 1 AU of the system, confirming that the stellar spin axis is aligned with the disks — consistent with a relatively undisturbed formation scenario. In addition, we detect non-uniform visibilities, non-zero closure phases, and additional Keplerian high-velocity components in the astrospectroscopy. These signatures are compatible with the presence of a third, inner disk at ~0.1 AU, potentially linked to reflected light from evaporating comets. However, further observations are required to confirm this interpretation, and it remains unclear whether such a disk, if present, would be stable over time. This alignment result showcases the power of GRAVITY+ for unveiling the architectures of directly imaged systems, while the possible inner disk remains a tantalizing — but as yet unconfirmed — target for future observations and modeling.