The breaking of cold traps and onset of titanium in ultra-hot Jupiter atmospheres: WASP-189b in context

@misc{pelletier2026breaking,
  title = {{The breaking of cold traps and onset of titanium in ultra-hot Jupiter atmospheres: WASP-189b in context}},
  author = {Stefan Pelletier and Romain Allart and Valentina Vaulato and David Ehrenreich and Eduardo Cristo and Laurie Dauplaise and Christophe Lovis and Leslie Moranta and Nicolas B. Cowan and Thierry Forveille and Étienne Artigau and Frédérique Baron and Susana C. C. Barros and Björn Benneke and Xavier Bonfils and François Bouchy and Marta Bryan and Bruno L. Canto Martins and Ryan Cloutier and Neil J. Cook and Jose Renan De Medeiros and Xavier Delfosse and René Doyon and Jonay I. González Hernández and David Lafrenière and Izan de Castro Leão and Lison Malo and Claudio Melo and Lucile Mignon and Christoph Mordasini and Francesco Pepe and Rafael Rebolo and Jason Rowe and Nuno C. Santos and Damien Ségransan and Alejandro Suárez Mascareño and Stéphane Udry and Diana Valencia and Gregg Wade and Charles Cadieux and Lisa Dang and Emily Deibert and Xavier Dumusque and Dasaev O. Fontinele and Yolanda G. C. Frensch and Frédéric Genest and Roseane de Lima Gomes and Nicole Gromek and Melissa J. Hobson and Vigneshwaran Krishnamurthy and Khaled Al Moulla and Ares Osborn and Caroline Piaulet-Ghorayeb and Bennett Neil Skinner and Avidaan Srivastava and Atanas K. Stefanov and Joost P. Wardenier and Drew Weisserman and Vincent Yariv},
  howpublished = {arXiv},
  year = {2026},
  month = jun,
  doi = {10.48550/arxiv.2606.15934},
  eprint = {2606.15934},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2606.15934},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - The breaking of cold traps and onset of titanium in ultra-hot Jupiter atmospheres: WASP-189b in context
AU  - Stefan Pelletier
AU  - Romain Allart
AU  - Valentina Vaulato
AU  - David Ehrenreich
AU  - Eduardo Cristo
AU  - Laurie Dauplaise
AU  - Christophe Lovis
AU  - Leslie Moranta
AU  - Nicolas B. Cowan
AU  - Thierry Forveille
AU  - Étienne Artigau
AU  - Frédérique Baron
AU  - Susana C. C. Barros
AU  - Björn Benneke
AU  - Xavier Bonfils
AU  - François Bouchy
AU  - Marta Bryan
AU  - Bruno L. Canto Martins
AU  - Ryan Cloutier
AU  - Neil J. Cook
AU  - Jose Renan De Medeiros
AU  - Xavier Delfosse
AU  - René Doyon
AU  - Jonay I. González Hernández
AU  - David Lafrenière
AU  - Izan de Castro Leão
AU  - Lison Malo
AU  - Claudio Melo
AU  - Lucile Mignon
AU  - Christoph Mordasini
AU  - Francesco Pepe
AU  - Rafael Rebolo
AU  - Jason Rowe
AU  - Nuno C. Santos
AU  - Damien Ségransan
AU  - Alejandro Suárez Mascareño
AU  - Stéphane Udry
AU  - Diana Valencia
AU  - Gregg Wade
AU  - Charles Cadieux
AU  - Lisa Dang
AU  - Emily Deibert
AU  - Xavier Dumusque
AU  - Dasaev O. Fontinele
AU  - Yolanda G. C. Frensch
AU  - Frédéric Genest
AU  - Roseane de Lima Gomes
AU  - Nicole Gromek
AU  - Melissa J. Hobson
AU  - Vigneshwaran Krishnamurthy
AU  - Khaled Al Moulla
AU  - Ares Osborn
AU  - Caroline Piaulet-Ghorayeb
AU  - Bennett Neil Skinner
AU  - Avidaan Srivastava
AU  - Atanas K. Stefanov
AU  - Joost P. Wardenier
AU  - Drew Weisserman
AU  - Vincent Yariv
PY  - 2026
DA  - 2026/06/14
PB  - arXiv
DO  - 10.48550/arxiv.2606.15934
UR  - https://arxiv.org/abs/2606.15934
AB  - Condensates are ubiquitous to all Solar System planets with significant (>10mbar) atmospheres. The same is true for most exoplanets with characterised atmospheres, with even ultra-hot exoplanets being able to form clouds on their cooler nightsides. One high-interest condensate is titanium, a highly refractory element that as an oxide (TiO) is a potent optical absorber long believed to be a driver of thermal inversions in highly irradiated exoplanet atmospheres. Observations have shown that some ultra-hot Jupiters have strong thermal inversions despite being significantly Ti-depleted, likely due to cold trapping, raising doubts about whether TiO is the main cause of their inverted temperature structures. Our aim was to retrieve the titanium-to-iron ratio of the dayside atmosphere of the ultra-hot Jupiter WASP-189b to determine whether the full titanium budget is accounted for in the gas phase. We analysed thermal emission observations of WASP-189b taken with the HARPS and NIRPS spectrographs using different atmospheric retrieval prescriptions to infer the planet's atmospheric thermal structure and composition. We observed Fe and Ti signals in cross-correlation and measured a sub-solar Ti/Fe ratio for WASP-189b using both free and chemical equilibrium retrieval approaches. We find the Ti/Fe of the planetary atmosphere to be between 28% and 81% (1-σ bounds) that of the stellar value. The slight underabundance of Ti with respect to Fe on the dayside atmosphere of WASP-189b suggests that some titanium is missing from the gas phase, potentially due to a partial nightside cold trap. In the context of the ultra-hot Jupiter population, the onset of titanium in exoplanetary atmospheres appears to occur progressively, coinciding not with when thermal inversions begin but rather when the vapourisation threshold of titanium is reached on the nightside.
ER  -