Two inner dust clumps in PDS 70

We consistently detect two inner emission features with SPHERE: one corresponding to the previously proposed planet candidate at ~13au, and another that appears to share the same orbit while leading it by ~120deg (clockwise direction) with a more elongated morphology. Both features exhibit dust-scattered light spectra while displaying different colors, which may indicate differences in dust grain sizes. We show that such configuration is consistent with co-orbital dust accumulated at the stable Lagrangian regions of a yet undetected planet, distinct from the previously proposed candidate.

The analysis of GRAVITY data at the predicted position of this newly proposed planet has resulted in a marginal (3sigma) detection located between the two clumps along the same orbit (rho=76.2+/-0.29mas, PA=226.50+/-0.21deg), and consistent with a ~3M_{Jup}_ planet. This planet-like signal is aligned with a narrow shadow detected in the outer disk with SPHERE. Additionally, we detect with SPHERE some polarized emission very close to the star likely arising from the inner disk, from which we roughly estimate an inclination of 50deg and a PA of ~135deg .

The fact that the two dust clumps appear embedded within this polarized emission motivates an inner disk-related alternative scenario. We conclude that the emission from the previously reported third planet candidate could arise either from a dust clump trailing a yet undetected planet along the same orbit, or from a rotating substructure within the inner disk. Additional observations are required to further test these two proposed scenarios.

In particular, confirming the new GRAVITY planet-like signal would support the use of co-orbital substructures as indirect tracers of embedded planets.