Tess Data Refines WASP-12 B Ephemeris through Detailed Transit Photometry Analysis

The ultra-hot Jupiter WASP-12 b has been the subject of intense scrutiny as astronomers seek to understand the behaviour of exoplanets close to their stars. Chinedu Jude Nnaji, from the University of the Witwatersrand, alongside colleagues, have now presented a detailed analysis of this planet using data gathered by the Transiting Exoplanet Survey Satellite (TESS). Their work focuses on refining the known timing of WASP-12 b’s transits , its passages in front of its host star , and precisely measuring its physical characteristics. This research is significant because accurate transit timings and planetary parameters are crucial for modelling the planet’s atmosphere and understanding the complex physical processes at play in such extreme environments, paving the way for future investigations. The team’s refined ephemeris, derived from TESS photometry, will improve the accuracy of predicted transit times and support further study of this uniquely inflated exoplanet.

Their work focuses on refining the known timing of WASP-12 b’s transits and precisely measuring its physical characteristics. This research is significant because accurate transit timings and planetary parameters are crucial for modelling the planet’s atmosphere and understanding the complex physical processes at play in such extreme environments, paving the way for future investigations.

The team’s refined ephemeris, derived from TESS photometry, will improve the accuracy of predicted transit times and support further study of this uniquely inflated exoplanet. The study is based on publicly available calibrated light curves and target pixel files accessed through the Mikulski Archive for Space Telescopes (MAST) cloud infrastructure. Analysis of four transits observed by TESS yielded mid-transit times of 2458982.2784 ±0.0006, 2458988.9917 ±0.0005, 2458995.7061 ±0.0007 and 2459002.4214 ±0.0008 Barycentric Dynamical Time respectively. These observations allowed for a refinement of the ephemeris of WASP-12 b, resulting in a new mid-transit time of 2458991.3491 ±0.0005 BDT and an orbital period of 1.0914036 ±0.0000013 days.

WASP-12 b Transit Modelling with TESS Data

The research team undertook a detailed photometric analysis of WASP-12 b, leveraging publicly available calibrated data from TESS. Scientists accessed both light curves and target pixel files through the Mikulski Archive for Space Telescopes (MAST) cloud infrastructure, forming the foundation for a rigorous investigation of the exoplanet’s transit characteristics. Following extraction and normalization of the photometric time series, the study employed a physical transit model to meticulously determine the system’s geometric parameters, including the planet-to-star radius ratio, orbital inclination, impact parameter, and transit duration.

To achieve precise measurements, the study pioneered a stepwise methodology beginning with phase-folding the light curve using an initial ephemeris. This process combined all transit events into a single, high signal-to-noise profile, subsequently fitted with the ‘batman’ package, which implements the Mandel & Agol (2002) analytic transit model. The team adopted a quadratic limb-darkening law, utilizing literature values appropriate for WASP-12’s stellar parameters and assuming zero orbital eccentricity, consistent with prior investigations. This careful modeling allowed for the computation of the transit duration and the derivation of the impact parameter, offering crucial insights into the orbital configuration.

Further refining the analysis, researchers extracted individual mid-transit times for each observed transit. A physical transit model was fitted to fixed temporal windows surrounding predicted mid-transit times, allowing only the mid-transit time and flux normalization to vary while maintaining fixed geometric parameters. This innovative approach minimized degeneracies between transit shape and timing, yielding precise measurements and associated uncertainties. These individual timings were then subjected to a weighted least-squares fit to refine the orbital ephemeris, with the inverse squared timing uncertainties serving as weights.

The resulting refined orbital period and reference epoch significantly improve the predictive accuracy of future transit times within the TESS observational baseline. An observed-minus-calculated (O-C) analysis, comparing measured transit times to those predicted by the refined ephemeris, revealed no statistically significant transit timing variations, confirming the consistency of the data with a linear ephemeris. This work demonstrates the power of TESS photometry to deliver precise transit characterization and ephemeris refinement, providing updated parameters essential for future atmospheric and dynamical investigations of WASP-12 b.

WASP-12 b’s Refined Orbit and Ephemeris

Scientists conducted a detailed analysis of WASP-12 b, utilising data obtained from TESS. The research team accessed publicly available calibrated light curves and target pixel files through the Mikulski Archive for Space Telescopes (MAST) cloud infrastructure to perform a transit photometric analysis. After normalising the photometric time series, the light curve was phase-folded and modelled with a physical transit model, allowing for the precise determination of the system’s geometric parameters.

This work demonstrates the capability of TESS photometry to provide precise transit characterisation and ephemeris refinement for well-studied exoplanet systems. Experiments revealed a refined orbital period and reference epoch, improving the predictive accuracy of future transit times over the TESS observational baseline. The team measured individual mid-transit times and employed a weighted linear fit to achieve this improved precision. An observed-minus-calculated (O-C) analysis showed no statistically significant transit timing variations, confirming that the timing data are consistent with a linear ephemeris within the measurement uncertainties.

This consistency is crucial for future observations and modelling of the WASP-12 b system. The study derived the planetary radius and transit depth, confirming the highly inflated nature of WASP-12 b, a planet with an orbital period of approximately 1.09 days. Measurements confirm the planet-to-star radius ratio, orbital inclination, impact parameter, and transit duration, providing a comprehensive set of parameters for this extreme exoplanet. Data shows that TESS observations capture a large number of transit events, enabling both precise transit shape modelling and independent measurements of individual mid-transit times.

WASP-12 b’s Radius and Orbital Refinement

This work presents a detailed analysis of WASP-12 b, utilising photometric data gathered by TESS. Through careful modelling of the planet’s transits, researchers have refined the system’s geometric parameters, including the planetary radius and orbital inclination, confirming the previously established highly inflated nature of WASP-12 b. Furthermore, precise measurements of transit timings have allowed for an improved orbital ephemeris, enhancing the accuracy of future transit predictions.

The significance of this study lies in its demonstration of TESS’s continued utility for characterising known exoplanet systems with high precision. While the analysis revealed no statistically significant transit timing variations, suggesting a stable orbital configuration, the refined parameters provide a crucial foundation for upcoming investigations. The authors acknowledge the limitations imposed by the current observational baseline and suggest that longer-term monitoring, potentially combined with data from other sources, could reveal subtle dynamical effects. Future research focusing on extended temporal baselines and complementary observations will be essential to fully understand the long-term evolution and dynamical architecture of this extreme planetary system.