Kavli Affiliate: David Charbonneau
| First 5 Authors: Juliana García-Mejía, Zoë L. de Beurs, Patrick Tamburo, Andrew Vanderburg, David Charbonneau
| Summary:
We present a ground-based transit detection of HIP 41378 f, a long-period ($P
= 542$ days), extremely low-density ($0.09 pm 0.02$ g cm$^{-3}$) giant
exoplanet in a dynamically complex system. Using photometry from Tierras,
TRAPPIST-North, and multiple LCOGT sites, we constrain the transit center time
to $T_{C,6} = 2460438.889 pm 0.049$ BJD TDB. This marks only the second
ground-based detection of HIP 41378 f, currently the longest-period and
longest-duration transiting exoplanet observed from the ground. We use this new
detection to update the TTV solution for HIP 41378 f and refine the predicted
times of its next two transits in November 2025 and April 2027. Incorporating
new TESS Sector 88 data, we also rule out the 101-day orbital period alias for
HIP 41378 d, and find that the remaining viable solutions are centered on the
278, 371, and 1113-day aliases. The latter two imply dynamical configurations
that challenge the canonical view of planet e as the dominant perturber of
planet f. Our results suggest that HIP 41378 d may instead play the leading
role in shaping the TTV of HIP 41378 f.
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