Spot-Crossing Variations Confirm a Misaligned Orbit for a Planet Transiting an M Dwarf
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| Format: | Preprint |
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2025
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| _version_ | 1866911089739956224 |
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| author | Tamburo, Patrick Yee, Samuel W. García-Mejía, Juliana Charbonneau, David Bieryla, Allyson Collins, Karen A. Shporer, Avi |
| author_facet | Tamburo, Patrick Yee, Samuel W. García-Mejía, Juliana Charbonneau, David Bieryla, Allyson Collins, Karen A. Shporer, Avi |
| contents | 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 \textit{Tierras} 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, $ψ_\star$. The data are best described by a planet on a misaligned orbit around a highly inclined star ($ψ_\star = {77.4^\circ} ^{+2.3^\circ}_{-2.5^\circ}$; $i_\star = {22.3^\circ}^{+1.8^\circ}_{-1.6^\circ}$) that hosts a large polar starspot ($r_\mathrm{spot} = {31.2^\circ}^{+2.4^\circ}_{-1.9^\circ}$; $λ_\mathrm{spot} = {80.5^\circ}\pm1.2^\circ$). 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2506_11998 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Spot-Crossing Variations Confirm a Misaligned Orbit for a Planet Transiting an M Dwarf Tamburo, Patrick Yee, Samuel W. García-Mejía, Juliana Charbonneau, David Bieryla, Allyson Collins, Karen A. Shporer, Avi Earth and Planetary Astrophysics Solar and Stellar Astrophysics 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 \textit{Tierras} 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, $ψ_\star$. The data are best described by a planet on a misaligned orbit around a highly inclined star ($ψ_\star = {77.4^\circ} ^{+2.3^\circ}_{-2.5^\circ}$; $i_\star = {22.3^\circ}^{+1.8^\circ}_{-1.6^\circ}$) that hosts a large polar starspot ($r_\mathrm{spot} = {31.2^\circ}^{+2.4^\circ}_{-1.9^\circ}$; $λ_\mathrm{spot} = {80.5^\circ}\pm1.2^\circ$). 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. |
| title | Spot-Crossing Variations Confirm a Misaligned Orbit for a Planet Transiting an M Dwarf |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2506.11998 |