Most known planets are found around metal-rich host stars, which has made it difficult to determine whether a lower metallicity limit for planet formation exists and how the properties of planets born in low-metallicity environments may differ from those with metal-rich origins. We present the discovery and characterization of TOI-7169 b (TIC 372048733 b), a hot Jupiter that is orbiting a spectroscopically-confirmed metal-poor ([Fe/H] = -0.72 +/- 0.05) host star. Based on photometry from TESS and follow-up ground-based imaging, we measure an orbital period of 3.4373125 d and a planetary radius of 1.475 +/- 0.029 R_Jup. We use TRES spectroscopy to determine a mass for TOI-7169 b of 0.41 +/- 0.14 M_Jup. The planet is therefore inflated, with a low density of 0.159 +0.055/-0.054 g/cm^3. We also characterize the host star, showing that TOI-7169 is ancient (12.3 +/- 0.6 Gyr) and alpha-enhanced ([alpha/Fe] ~ 0.3), but with a Galactocentric orbit that is confined to the thin disk. TOI-7169 is perhaps the oldest and most metal-poor star currently known to host a transiting giant planet. Future transmission spectroscopy probing the atmosphere of TOI-7169 b may provide insight into the effect of metallicity on the physical properties of giant planets.
@article{arxiv.2603.25787,
title = {TOI-7169 b: A Hot Jupiter Transiting a Metal-Poor Star},
author = {Joshua D. Simon and Joseph E. Rodriguez and Jhon Yana Galarza and David W. Latham and Victoria DiTomasso and Karen A. Collins and Jack Schulte and Anirudh Chiti and Samuel N. Quinn and Mohammad K. Mardini and Shubham Kanodia and Johanna K. Teske and Peter S. Ferguson and Samuel W. Yee and T. G. Tan and Khalid Alsubai and Khalid Barkaoui and Zouhair Benkhaldoun and Krzysztof Bernacki and Jaikrit Bhattacharya and Jerome P. de Leon and Sarah J. Deveny and Mark E. Everett and Izuru Fukuda and Akihiko Fukui and Michael Gillon and Arvind F. Gupta and Steve B. Howell and Emmanuel Jehin and Gaia Lacedelli and Adam Lark and Colin Littlefield and Felipe Murgas and Norio Narita and Enric Palle and Hannu Parviainen and Adam Popowicz and Richard P. Schwarz and Avi Shporer and Abderahmane Soubkiou and Francis P. Wilkin},
journal= {arXiv preprint arXiv:2603.25787},
year = {2026}
}
Comments
20 pages, 9 figures, 6 tables. Submitted to AAS Journals