Transit Timing Variations of the Sub-Saturn Exoplanet HAT-P-12b

Abstract

We present Transit Timing Variations (TTVs) of HAT-P-12b, a low-density sub-Saturn mass planet orbiting a metal-poor K4 dwarf star. Using 14 years of observational data (2009-2022), our study incorporates 7 new ground-based photometric transit observations, three sectors of Transiting Exoplanet Survey Satellite (TESS) data, and 23 previously published light curves. A total of 46 light curves were analyzed using various analytical models, such as linear, orbital decay, apsidal precession, and sinusoidal models to investigate the presence of additional planets. The stellar tidal quality factor ($Q_{\star }^{\prime }\sim$ 28.4) is lower than the theoretical predictions, making the orbital decay model an unlikely explanation. The apsidal precession model with a ${\chi }_r^2$ of 4.2 revealed a slight orbital eccentricity (e = 0.0013) and a precession rate of 0.0045 rad/epoch. Frequency analysis using the Generalized Lomb-Scargle (GLS) periodogram identified a significant periodic signal at 0.00415 cycles/day (FAP = 5.1$\times$10${}^{-6}$ %), suggesting the influence of an additional planetary companion. The sinusoidal model provides the lowest reduced chi-squared value (${\chi }_r^2$) of 3.2. Sinusoidal fitting of the timing residuals estimated this companion to have a mass of approximately 0.02 $M_J$ , assuming it is in a 2:1 Mean-Motion Resonance (MMR) with HAT-P-12b. Additionally, the Applegate mechanism, with an amplitude much smaller than the observed TTV amplitude of 156 s, confirms that stellar activity is not responsible for the observed variations.

28 pages, 5 figures, 8 tables, accepted by New Astronomy

References in corpus (9)

• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• DHP Framework: Digital Health Passports Using Blockchain -- Use case on international tourism during the COVID-19 pandemic
• EXOFAST: A fast exoplanetary fitting suite in IDL
• HAT-P-12b: A Low-Density Sub-Saturn Mass Planet Transiting a Metal-Poor K Dwarf
• Probing Transit Timing Variation and its Possible Origin with Twelve New Transits of TrES-3b
• Searching for Candidates of Orbital Decays among Transit Exoplanets
• Revisiting the Transit Timing Variations in the TrES-3 and Qatar-1 systems with TESS data
• The Transit Timing and Atmosphere of Hot Jupiter HAT-P-37b