Presentation #104.03 in the session Transits 1.
In this talk, we present the results from an extensive four-year long follow-up campaign of the TRAPPIST-1 (T-1) system led from the ground with the SPECULOOS and Liverpool Telescopes. This represents 285 nights of observations, 269 new transits of the seven planets, and includes 3 months of daily monitoring of the star to study its photometric variability.
First of all, to understand the origin of the existing inconsistency between K2 and Spitzer photometric variability, we derive the rotation period of the host star in the I+z band and use it to propose a spot variability model that would agree with the observations in each band and at the same time provide insights on the nature (proportion and temperature) of the photospheric heterogeneities on the surface of T-1, in a similar way as in Morris et al. (2018). From those outcomes we discuss the expected impact of stellar contamination on the planetary spectra via the transit light source effect. In parallel, we present our statistics of spot-like and faculae-like crossing events on all observed transits and relate them to the photometric modulations.
In addition, we analyze 269 new transits in order to (1) refine the planets’ parameters using individual and global analyses and (2) derive precise transit timing variations for the seven planets. We show that recent timings (most recent ones from Nov 2021) of planet h seem to slightly deviate from the predictions by Agol et al. (2021), implying either that planet h’s timings have an excess of outliers or that a 7-planet model is no longer a good fit, which could suggest the existence of a putative eighth planet. To figure this out, we show the results of new optimization runs with 7-planet and 8-planet models and including periodic orbit (P-O) — families of solutions to the N-body problem — constraints. Indeed, near-resonant planetary system such as T-1 are expected to reside in the dynamical neighborhood of stable P-Os (Antoniadou et al. (2020)) and such a configuration can be used to yield better constraints on the orbital elements.
Finally, we look at T-1’s flaring activity. On one hand, we compute flare occurrence rates and energies to compute flare frequency distribution and complement the work initiated by Ducrot et al. (2020) on placing the T-1 planets relative to the abiogenesis zone introduced by Rimmer et al. (2018). On the other hand, we seek correlations between flaring events and periodic photometric variability to state whether the observation of Morris et al (2018) claiming that visible flares seem to occur preferentially when the star is bright, and when the brightness is increasing most rapidly, is confirmed or not.