A Compact, Coherent Representation of Stellar Surface Variation in the Spectral Domain
Time-varying inhomogeneities on stellar surfaces constitute one of the largest sources of radial velocity (RV) error for planet detection and characterization. We show that stellar variations, because they manifest on coherent, rotating surfaces, give rise to changes that are complex but usably comp...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2024-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad90ad |
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| _version_ | 1850108272119382016 |
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| author | Lily L. Zhao Megan Bedell David W. Hogg Rodrigo Luger |
| author_facet | Lily L. Zhao Megan Bedell David W. Hogg Rodrigo Luger |
| author_sort | Lily L. Zhao |
| collection | DOAJ |
| description | Time-varying inhomogeneities on stellar surfaces constitute one of the largest sources of radial velocity (RV) error for planet detection and characterization. We show that stellar variations, because they manifest on coherent, rotating surfaces, give rise to changes that are complex but usably compact and coherent in the spectral domain. Methods for disentangling stellar signals in RV measurements benefit from modeling the full domain of spectral pixels. We simulate spectra of spotted stars using starry and construct a simple spectrum projection space that is sensitive to the orientation and size of stellar surface features. Regressing measured RVs in this projection space reduces RV scatter by 60%–80% while preserving planet shifts. We note that stellar surface variability signals do not manifest in spectral changes that are purely orthogonal to a Doppler shift or exclusively asymmetric in line profiles; enforcing orthogonality or focusing exclusively on asymmetric features will not make use of all the information present in the spectra. We conclude with a discussion of existing and possible implementations on real data based on the presented compact, coherent framework for stellar signal mitigation. |
| format | Article |
| id | doaj-art-dac9d7dc8a554cc089eb3740bed4887a |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-dac9d7dc8a554cc089eb3740bed4887a2025-08-20T02:38:25ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-01977214010.3847/1538-4357/ad90adA Compact, Coherent Representation of Stellar Surface Variation in the Spectral DomainLily L. Zhao0https://orcid.org/0000-0002-3852-3590Megan Bedell1https://orcid.org/0000-0001-9907-7742David W. Hogg2https://orcid.org/0000-0003-2866-9403Rodrigo Luger3https://orcid.org/0000-0002-0296-3826Center for Computational Astrophysics, Flatiron Institute , 162 Fifth Avenue, New York, NY 10010, USA; Department of Astronomy & Astrophysics, University of Chicago , 5640 S Ellis Avenue, Chicago, IL 60637, USACenter for Computational Astrophysics, Flatiron Institute , 162 Fifth Avenue, New York, NY 10010, USACenter for Computational Astrophysics, Flatiron Institute , 162 Fifth Avenue, New York, NY 10010, USA; Center for Cosmology and Particle Physics, Department of Physics, New York University , 726 Broadway, New York, NY 10003, USA; Center for Data Science, New York University , 60 Fifth Avenue, New York, NY 10011, USA; Max-Planck-Institut für Astronomie , Königstuhl 17, D-69117 Heidelberg, GermanyCenter for Computational Astrophysics, Flatiron Institute , 162 Fifth Avenue, New York, NY 10010, USATime-varying inhomogeneities on stellar surfaces constitute one of the largest sources of radial velocity (RV) error for planet detection and characterization. We show that stellar variations, because they manifest on coherent, rotating surfaces, give rise to changes that are complex but usably compact and coherent in the spectral domain. Methods for disentangling stellar signals in RV measurements benefit from modeling the full domain of spectral pixels. We simulate spectra of spotted stars using starry and construct a simple spectrum projection space that is sensitive to the orientation and size of stellar surface features. Regressing measured RVs in this projection space reduces RV scatter by 60%–80% while preserving planet shifts. We note that stellar surface variability signals do not manifest in spectral changes that are purely orthogonal to a Doppler shift or exclusively asymmetric in line profiles; enforcing orthogonality or focusing exclusively on asymmetric features will not make use of all the information present in the spectra. We conclude with a discussion of existing and possible implementations on real data based on the presented compact, coherent framework for stellar signal mitigation.https://doi.org/10.3847/1538-4357/ad90adSpectroscopyRadial velocityAstronomy data analysisStellar activity |
| spellingShingle | Lily L. Zhao Megan Bedell David W. Hogg Rodrigo Luger A Compact, Coherent Representation of Stellar Surface Variation in the Spectral Domain The Astrophysical Journal Spectroscopy Radial velocity Astronomy data analysis Stellar activity |
| title | A Compact, Coherent Representation of Stellar Surface Variation in the Spectral Domain |
| title_full | A Compact, Coherent Representation of Stellar Surface Variation in the Spectral Domain |
| title_fullStr | A Compact, Coherent Representation of Stellar Surface Variation in the Spectral Domain |
| title_full_unstemmed | A Compact, Coherent Representation of Stellar Surface Variation in the Spectral Domain |
| title_short | A Compact, Coherent Representation of Stellar Surface Variation in the Spectral Domain |
| title_sort | compact coherent representation of stellar surface variation in the spectral domain |
| topic | Spectroscopy Radial velocity Astronomy data analysis Stellar activity |
| url | https://doi.org/10.3847/1538-4357/ad90ad |
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