Paper

TOI-7169 b: A Hot Jupiter Transiting a Metal-Poor Star

Bhattacharya, Jaikrit, Simon, Joshua D, Lark, Adam, Soubkiou, Abderahmane, Chiti, Anirudh, Yee, Samuel W, Gupta, Arvind F, DiTomasso, Victoria, Murgas, Felipe, Wilkin, Francis P, Howell, Steve B, Schwarz, Richard P, de Leon, Jerome P, Alsubai, Khalid, Fukuda, Izuru, Littlefield, Colin, Shporer, Avi, Deveny, Sarah J, Rodriguez, Joseph E, Ferguson, Peter S, Latham, David W, Quinn, Samuel N, Gillon, Michael, Jehin, Emmanuel, Parviainen, Hannu, Schulte, Jack, Bernacki, Krzysztof, Barkaoui, Khalid, Collins, Karen A, Mardini, Mohammad K, Jhon Yana Galarza, Everett, Mark E, Benkhaldoun, Zouhair, Palle, Enric, Lacedelli, Gaia, Popowicz, Adam, Tan, T G, Fukui, Akihiko, Teske, Johanna K, Kanodia, Shubham, Narita, Norio

2026

Overview

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.

• Publisher: Cornell University Library, arXiv.org
• Subject: Extrasolar planets / Gas giant planets / Iron / Jupiter / Metallicity / Orbits / Physical properties / Planet formation / Spectroscopy / Spectrum analysis