2025/04/15 by David Trevascus, Trevascus, David, Sarah Blunt +47 · 1 voice · 2 citations
Physics and Astronomy · #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #astro-ph.EP
paper · pdf · doi:10.48550/arxiv.2504.11210
arxiv published 2025/04/15 · arxiv updated 2025/05/13
Hot- and cold-start planet formation models predict differing luminosities for the young, bright planets that direct imaging surveys are most sensitive to. However, precise mass estimates are required to distinguish between these models observationally. The presence of two directly imaged planets, PDS 70 b and c, in the PDS 70 protoplanetary disk provides us a unique opportunity for dynamical mass measurements, since the masses for these planets are currently poorly constrained. Fitting orbital parameters to new astrometry of these planets, taken with VLTI/GRAVITY in the K~band, we find 2σ dynamical upper mass limits of 4.9 M\rm Jup for b and 13.6 M\rm Jup for c. Adding astrometry from the newly proposed planet candidate PDS 70 d into our model, we determine 2σ dynamical upper mass limits of 5.3 M\rm Jup, 7.5 M\rm Jup and 2.2 M\rm Jup for b, c, and the candidate d respectively. However, N-body analysis of the orbits fit in this case suggest that the inclusion of d makes the system unstable. Using the upper mass limits for b and c we rule out the coldest-start formation models for both planets, calculating minimum post-formation entropies (Si) of 9.5 k\rm B/\rm baryon and 8.4 k\rm B/\rm baryon respectively. This places PDS 70 b and c on the growing list of directly-imaged planets inconsistent with cold-start formation.