Ephemeris Refinement for Qatar-4 b, HAT-P-18 b, and CoRoT-1 b with Small Telescope and TESS Observations

Heather B. Hewitt; Mikaela Chamlee; Trinity Hockman; Annalise Igyarto; Dan van der Burg; Federico R. Noguer; Ira Bell; Jeremie Abides; Simon Abshear; Philip Arthur Ellis; Shashank Avinash Araokar; Eurico Bras; Jamie Buckingham; Dion Bumpus; Kartavya Chauhan; Logan Conrad; Koty Creel; Courtney Dammann; Samantha Duarte Rodriguez; Jeffrey Ensor; Benjamen Erickson; Adam Facciponti; Logan Farrar; Blaise Foca; Holly Foreman; Mark Foreman; Haley Fournier; Jeff Franklin; Keith Goss; Dustin Hubbartt; Nicolette Jeantilus; Justin Kobrin; Spencer Lunsford; Wyatt McCormick; Zachary McNeely; Kurtis Merrill; Sarah Miller; Dean Miller; Sofie Miura; Cody Montgomery; Karina Munoz; Keith Norton; Anna Plum; Jake Raby; Jay Thompson; Sohley Wallace-Pichardo; Molly N. Simon; Robert T. Zellem

arXiv · 2607.15391

Ephemeris Refinement for Qatar-4 b, HAT-P-18 b, and CoRoT-1 b with Small Telescope and TESS Observations

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Abstract

We present updated transit timing measurements for three hot Jupiters (Qatar-4 b, HAT-P-18 b, and CoRoT-1 b) by leveraging data collected from the MicroObservatory Telescope Network, a network of small, robotic ground-based telescopes, and the NASA Transiting Exoplanet Survey Satellite (TESS). By combining these data with archival published results, we present the most precise orbital solutions to date for all three systems, allowing for precise transit time predictions for future missions. We report an updated mid-transit time for Qatar-4 b of 2458919.5838 $\pm$ 0.000089 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 1.80536560 $\pm$ 0.00000021 days. For HAT-P-18 b, we find a mid-transit time of 2459743.85340 $\pm$ 0.000022 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 5.50802957 $\pm$ 0.00000012 days. For CoRoT-1 b, we report a mid-transit time of 2456268.99083 $\pm$ 0.000099 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 1.50896846 $\pm$ 0.000000071 days. Our results demonstrate improvements over recently published ephemerides, with reductions of 36.4%, 4.35%, and 17.5% in mid-transit time uncertainties and 65.0%, 77.4%, and 16.9% in orbital period uncertainties for Qatar-4 b, HAT-P-18 b, and CoRoT-1 b, respectively. The results of this study improve the precision of future transit predictions and demonstrate the value of coordinated small-telescope monitoring (and citizen science initiatives) when updating the orbital parameters of hot Jupiters.

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Heather B. Hewitt, Mikaela Chamlee, Trinity Hockman, Annalise Igyarto, Dan van der Burg, Federico R. Noguer, Ira Bell, Jeremie Abides, Simon Abshear, Philip Arthur Ellis, Shashank Avinash Araokar, Eurico Bras, Jamie Buckingham, Dion Bumpus, Kartavya Chauhan, Logan Conrad, Koty Creel, Courtney Dammann, Samantha Duarte Rodriguez, Jeffrey Ensor, Benjamen Erickson, Adam Facciponti, Logan Farrar, Blaise Foca, Holly Foreman, Mark Foreman, Haley Fournier, Jeff Franklin, Keith Goss, Dustin Hubbartt, Nicolette Jeantilus, Justin Kobrin, Spencer Lunsford, Wyatt McCormick, Zachary McNeely, Kurtis Merrill, Sarah Miller, Dean Miller, Sofie Miura, Cody Montgomery, Karina Munoz, Keith Norton, Anna Plum, Jake Raby, Jay Thompson, Sohley Wallace-Pichardo, Molly N. Simon, Robert T. Zellem. 2026-07-16. Ephemeris Refinement for Qatar-4 b, HAT-P-18 b, and CoRoT-1 b with Small Telescope and TESS Observations. https://arxiv.org/abs/2607.15391

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