Determine the migration history of TOI-1839 b

Determine whether TOI-1839 b reached its present short-period orbit through high-eccentricity migration triggered by an undetected companion, dynamical interactions with TOI-1839 c, disk-driven migration, or in situ formation.

Background

TOI-1839 b lies near the tidal survival band but the current radial-velocity data show no significant long-term trend or detected outer giant companion. Nevertheless, gaps in the observations allow highly eccentric or longer-period companions to remain undetected.

The inner companion TOI-1839 c is unlikely to be a high-eccentricity-migration perturber because of its short orbital separation and low mass, although alternative dynamical interactions between the close-in planets remain possible. The authors therefore leave the origin of TOI-1839 b’s current orbit unresolved and identify the need for improved observations and theoretical and numerical studies.

References

Overall, whether TOI-1839~b reached the lower edge of the desert via HEM triggered by an as-yet undetected companion, through interactions with TOI-1839~c, or alternatively through disk-driven migration or in situ formation remains an open question that will require improved observational constraints together with dedicated theoretical and numerical studies.

— Two extremely irradiated volatile-rich sub-Neptunes with companions in the TOI-426 and TOI-1839 systems: Insights into arrival and survival near the lower edge of the Neptunian desert  (2609.05413 - Castro-González et al., 4 Sep 2026) in Section 4.3, Discussion, subsection “Outer giant companions to sub-Neptunes near the edge of the Neptunian desert”