Disks, Planets, and Planetary System Architectures with Asgard/BIFROST @ VLTI

We present the exoplanet and planet formation science case for a new beam combination instrument for the VLTI, named BIFROST. This instrument is funded through the European Research Council and has been proposed as part of the "Asgard Suite" of VLTI visitor instruments.

BIFROST will be the first VLTI instrument optimised for short wavelengths (1-1.6 mu) and high spectral resolution (up to R=25,000). This will allow us to measure the alignment between the stellar spin axis and the planetary orbital axis — even for wide-separation systems where this information is inaccessible with other techniques. These constraints will provide unique insights on the dynamical processes that shape system architectures, from stellar-mass companions down to planets.

To characterise the planets themselves, BIFROST will utilise off-axis interferometry, where adaptive optics is combined with star-light suppression from interferometry by placing the instrument fiber off-axis and adjusting the path delay to record at the predicted delay position of the planet. BIFROST will employ this method in J and H-band, providing access to molecular tracers that are highly complementary to the K-band probed by GRAVITY. This will provide further constraints for atmospheric retrieval.

Finally, we will discuss the prospect of using BIFROST to study accretion onto young planets. Resolving the gas kinematics in circumplanetary disks would enable a direct mass measurement and inform us how planets gain their mass.