Polka-dotted Stars: A Hierarchical Model for Mapping Stellar Surfaces Using Occultation Light Curves and the Case of TOI-3884
We present StarryStarryProcess , a novel hierarchical Bayesian framework for mapping stellar surfaces using exoplanet transit light curves. While previous methods relied solely on stellar rotational light curves—which contain limited information about spot properties—our approach leverages planetary...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/adf6be |
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| author | Sabina Sagynbayeva Will M. Farr Brett M. Morris Rodrigo Luger |
| author_facet | Sabina Sagynbayeva Will M. Farr Brett M. Morris Rodrigo Luger |
| author_sort | Sabina Sagynbayeva |
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| description | We present StarryStarryProcess , a novel hierarchical Bayesian framework for mapping stellar surfaces using exoplanet transit light curves. While previous methods relied solely on stellar rotational light curves—which contain limited information about spot properties—our approach leverages planetary transits as probes of stellar surfaces. When a planet crosses a spot during transit, it creates a distinctive change in the light curve that directly reveals spot properties. Our model integrates planetary transit modeling with stellar variability analysis by combining the spherical harmonic surface map representation from starry , the probabilistic approach to spot properties of StarryProcess , and a comprehensive transit model that accounts for spot-crossing events during transits. We demonstrate through synthetic data experiments that our model successfully recovers spot distributions, stellar orientation, and spot physical properties. We extend the framework to handle evolving stellar surfaces through time-dependent modeling. Applying our method to TESS observations of TOI-3884, we find evidence for high-latitude spot concentrations and significant spin–orbit misalignment. The transit-based approach overcomes fundamental limitations of previous models by providing constraints on spot properties that would remain hidden in the null space of rotational light curves alone. This methodology enables more accurate exoplanet characterization by disentangling stellar activity due to starspots from planetary signals while simultaneously providing insights into stellar magnetic activity patterns. The whole paper is reproducible and can be found by clicking the GitHub icon https://github.com/ssagynbayeva/polka-dotted-stars-toi3884/tree/main . |
| format | Article |
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| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-aa45b99ab0e34946b64eaaa6eb97e5c02025-08-25T14:55:55ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0199013210.3847/1538-4357/adf6bePolka-dotted Stars: A Hierarchical Model for Mapping Stellar Surfaces Using Occultation Light Curves and the Case of TOI-3884Sabina Sagynbayeva0https://orcid.org/0000-0002-6650-3829Will M. Farr1https://orcid.org/0000-0003-1540-8562Brett M. Morris2https://orcid.org/0000-0003-2528-3409Rodrigo Luger3https://orcid.org/0000-0002-0296-3826Department of Physics and Astronomy, Stony Brook University , Stony Brook, NY 11794, USA ; sabina.sagynbayeva@stonybrook.edu; Center for Computational Astrophysics, Flatiron Institute , New York, NY 10010, USA; Kavli Institute for Theoretical Physics, University of California , Santa Barbara, CA 93106, USADepartment of Physics and Astronomy, Stony Brook University , Stony Brook, NY 11794, USA ; sabina.sagynbayeva@stonybrook.edu; Center for Computational Astrophysics, Flatiron Institute , New York, NY 10010, USASpace Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USACenter for Computational Astrophysics, Flatiron Institute , New York, NY 10010, USAWe present StarryStarryProcess , a novel hierarchical Bayesian framework for mapping stellar surfaces using exoplanet transit light curves. While previous methods relied solely on stellar rotational light curves—which contain limited information about spot properties—our approach leverages planetary transits as probes of stellar surfaces. When a planet crosses a spot during transit, it creates a distinctive change in the light curve that directly reveals spot properties. Our model integrates planetary transit modeling with stellar variability analysis by combining the spherical harmonic surface map representation from starry , the probabilistic approach to spot properties of StarryProcess , and a comprehensive transit model that accounts for spot-crossing events during transits. We demonstrate through synthetic data experiments that our model successfully recovers spot distributions, stellar orientation, and spot physical properties. We extend the framework to handle evolving stellar surfaces through time-dependent modeling. Applying our method to TESS observations of TOI-3884, we find evidence for high-latitude spot concentrations and significant spin–orbit misalignment. The transit-based approach overcomes fundamental limitations of previous models by providing constraints on spot properties that would remain hidden in the null space of rotational light curves alone. This methodology enables more accurate exoplanet characterization by disentangling stellar activity due to starspots from planetary signals while simultaneously providing insights into stellar magnetic activity patterns. The whole paper is reproducible and can be found by clicking the GitHub icon https://github.com/ssagynbayeva/polka-dotted-stars-toi3884/tree/main .https://doi.org/10.3847/1538-4357/adf6beExoplanet astronomyStellar magnetic fieldsSurface variabilityAstrostatisticsAstrostatistics techniques |
| spellingShingle | Sabina Sagynbayeva Will M. Farr Brett M. Morris Rodrigo Luger Polka-dotted Stars: A Hierarchical Model for Mapping Stellar Surfaces Using Occultation Light Curves and the Case of TOI-3884 The Astrophysical Journal Exoplanet astronomy Stellar magnetic fields Surface variability Astrostatistics Astrostatistics techniques |
| title | Polka-dotted Stars: A Hierarchical Model for Mapping Stellar Surfaces Using Occultation Light Curves and the Case of TOI-3884 |
| title_full | Polka-dotted Stars: A Hierarchical Model for Mapping Stellar Surfaces Using Occultation Light Curves and the Case of TOI-3884 |
| title_fullStr | Polka-dotted Stars: A Hierarchical Model for Mapping Stellar Surfaces Using Occultation Light Curves and the Case of TOI-3884 |
| title_full_unstemmed | Polka-dotted Stars: A Hierarchical Model for Mapping Stellar Surfaces Using Occultation Light Curves and the Case of TOI-3884 |
| title_short | Polka-dotted Stars: A Hierarchical Model for Mapping Stellar Surfaces Using Occultation Light Curves and the Case of TOI-3884 |
| title_sort | polka dotted stars a hierarchical model for mapping stellar surfaces using occultation light curves and the case of toi 3884 |
| topic | Exoplanet astronomy Stellar magnetic fields Surface variability Astrostatistics Astrostatistics techniques |
| url | https://doi.org/10.3847/1538-4357/adf6be |
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