Kavli Affiliate: David Charbonneau
| First 5 Authors: Patrick Tamburo, Patrick Tamburo, , ,
| Summary:
TOI-3884~b is an unusual 6.4~R$_oplus$ planet orbiting an M4 host, whose
transits display large and persistent spot-crossing events. We used the
textitTierras Observatory to monitor both the long-term photometric
variability of TOI-3884 and changes in the spot-crossing events across multiple
transits of the planet. We show that the star rotates with a period of $11.020
pm 0.015$~days. We simultaneously model the rotational modulation of the star
and variations in transit shapes that arise due to rotation of the spot,
allowing us to determine the true stellar obliquity, $psi_star$. The data are
best described by a planet on a misaligned orbit around a highly inclined star
($psi_star = 77.4^circ ^+2.3^circ_-2.5^circ$; $i_star =
22.3^circ^+1.8^circ_-1.6^circ$) that hosts a large polar starspot
($r_mathrmspot = 31.2^circ^+2.4^circ_-1.9^circ$;
$lambda_mathrmspot = 80.5^circpm1.2^circ$). Archival photometry from
the Zwicky Transient Facility suggests that this polar spot has persisted on
TOI-3884 for at least seven years. The TOI-3884 system provides a benchmark for
studying the evolution of a polar spot on an M dwarf.
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