Evidence for LP 890-9d via Transit Timing Variations
Abstract
LP 890-9, also known as SPECULOOS-2 and TOI-4306, is a nearby late-M dwarf hosting two confirmed transiting rocky exoplanets. We analyze 20 JWST/NIRSpec PRISM transits of LP 890-9b and LP 890-9c obtained as part of GO program 7073 and detect statistically significant transit timing variations (TTVs), with peak-to-peak amplitudes of ~17 s and ~35 s, respectively. Using analytic linear TTV theory, we find that the known two-planet configuration cannot reproduce the measured TTV amplitudes or super-period, whereas three-planet models provide substantially better fits. The best-fit configuration places the candidate third planet, LP 890-9d, between planets b and c, with an orbital period of ~4.4 days; however, the current data do not uniquely determine its orbital architecture, and periods spanning 4.0-6.9 days remain plausible. TESS is insensitive to transits of LP 890-9d and we find no evidence for the candidate in JWST observations, although the phase coverage (ranging from ~50% to ~80%) depends strongly on the candidate orbital period. Additional high-precision transit observations of LP 890-9b and LP 890-9c are needed to refine their TTV solutions and further constrain the orbital properties of the third planet.
Related
- ExoEcho: Exoplanet Ephemerides Change Observations. III. A JWST Survey for Transit Timing Variations of 37 Exoplanets
- ExoEcho: Exoplanet Ephemerides Change Observations. III. A JWST Survey for Transit Timing Variations of 37 Exoplanets
- ExoMOD II. A Statistical Model of Transit Timing Variations in Kepler Multi-Planet Systems
- JWST and HST Confirm Transit Timing Variations for the Ultra-Hot Jupiter TOI-2109 b
- Toddlers in Resonance I: low masses and eccentricities of the 17 Myr giant planets HIP 67522 bc from transit timing variations
BibTeX
@misc{stevenson2026evidence,
title = {{Evidence for LP 890-9d via Transit Timing Variations}},
author = {Kevin B. Stevenson and Guangwei Fu and Kristin S. Sotzen and E. M. May and Larissa Palethorpe and Jacob Lustig-Yaeger and Ted M. Johnson and Eric Agol and Katherine A. Bennett and Carlos Gascón and David K. Sing and Jeff A. Valenti and Hannah R. Wakeford},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.05312},
eprint = {2609.05312},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.05312},
}
RIS
TY - UNPB
TI - Evidence for LP 890-9d via Transit Timing Variations
AU - Kevin B. Stevenson
AU - Guangwei Fu
AU - Kristin S. Sotzen
AU - E. M. May
AU - Larissa Palethorpe
AU - Jacob Lustig-Yaeger
AU - Ted M. Johnson
AU - Eric Agol
AU - Katherine A. Bennett
AU - Carlos Gascón
AU - David K. Sing
AU - Jeff A. Valenti
AU - Hannah R. Wakeford
PY - 2026
DA - 2026/09/04
PB - arXiv
DO - 10.48550/arxiv.2609.05312
UR - https://arxiv.org/abs/2609.05312
AB - LP 890-9, also known as SPECULOOS-2 and TOI-4306, is a nearby late-M dwarf hosting two confirmed transiting rocky exoplanets. We analyze 20 JWST/NIRSpec PRISM transits of LP 890-9b and LP 890-9c obtained as part of GO program 7073 and detect statistically significant transit timing variations (TTVs), with peak-to-peak amplitudes of ~17 s and ~35 s, respectively. Using analytic linear TTV theory, we find that the known two-planet configuration cannot reproduce the measured TTV amplitudes or super-period, whereas three-planet models provide substantially better fits. The best-fit configuration places the candidate third planet, LP 890-9d, between planets b and c, with an orbital period of ~4.4 days; however, the current data do not uniquely determine its orbital architecture, and periods spanning 4.0-6.9 days remain plausible. TESS is insensitive to transits of LP 890-9d and we find no evidence for the candidate in JWST observations, although the phase coverage (ranging from ~50% to ~80%) depends strongly on the candidate orbital period. Additional high-precision transit observations of LP 890-9b and LP 890-9c are needed to refine their TTV solutions and further constrain the orbital properties of the third planet.
ER -