Stellar Contamination Correction Using Back-to-back Transits of TRAPPIST-1 b and c
Stellar surface heterogeneities, such as spots and faculae, often contaminate exoplanet transit spectra, hindering precise atmospheric characterization. We demonstrate a novel, epoch-based, model-independent method to mitigate stellar contamination, applicable to multiplanet systems with at least on...
Saved in:
| Main Authors: | , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
|
| Series: | The Astrophysical Journal Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/2041-8213/ada5c7 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1849728916004012032 |
|---|---|
| author | Alexander D. Rathcke Lars A. Buchhave Julien de Wit Benjamin V. Rackham Prune C. August Hannah Diamond-Lowe João M. MendonÇa Aaron Bello-Arufe Mercedes López-Morales Daniel Kitzmann Kevin Heng |
| author_facet | Alexander D. Rathcke Lars A. Buchhave Julien de Wit Benjamin V. Rackham Prune C. August Hannah Diamond-Lowe João M. MendonÇa Aaron Bello-Arufe Mercedes López-Morales Daniel Kitzmann Kevin Heng |
| author_sort | Alexander D. Rathcke |
| collection | DOAJ |
| description | Stellar surface heterogeneities, such as spots and faculae, often contaminate exoplanet transit spectra, hindering precise atmospheric characterization. We demonstrate a novel, epoch-based, model-independent method to mitigate stellar contamination, applicable to multiplanet systems with at least one airless planet. We apply this method using quasi-simultaneous transits of TRAPPIST-1 b and TRAPPIST-1 c observed on 2024 July 9, with JWST/NIRSpec PRISM. These two planets, with nearly identical radii and impact parameters, are likely to either be bare rocks or possess thin, low-pressure atmospheres, making them ideal candidates for this technique, as variations in their transit spectra would be primarily attributed to stellar activity. Our observations reveal their transit spectra exhibit consistent features, indicating similar levels of stellar contamination. We use TRAPPIST-1 b to correct the transit spectrum of TRAPPIST-1 c, achieving a 2.5 × reduction in stellar contamination at shorter wavelengths. At longer wavelengths, lower signal-to-noise ratio prevents clear detection of contamination or full assessment of mitigation. Still, out-of-transit analysis reveals variations across the spectrum, suggesting contamination extends into the longer wavelengths. Based on the success of the correction at shorter wavelengths, we argue that contamination is also reduced at longer wavelengths to a similar extent. This shifts the challenge of detecting atmospheric features to a predominantly white noise issue, which can be addressed by stacking observations. This method enables epoch-specific stellar contamination corrections, allowing coaddition of planetary spectra for reliable searches of secondary atmospheres with signals of 60–250 ppm. Additionally, we identify small-scale cold (∼2000 K) and warm (∼2600 K) regions almost uniformly distributed on TRAPPIST-1, with overall covering fractions varying by ∼0.1% per hour. |
| format | Article |
| id | doaj-art-6039e0faefa54e57a7ed8582095fbce1 |
| institution | DOAJ |
| issn | 2041-8205 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Letters |
| spelling | doaj-art-6039e0faefa54e57a7ed8582095fbce12025-08-20T03:09:24ZengIOP PublishingThe Astrophysical Journal Letters2041-82052025-01-019791L1910.3847/2041-8213/ada5c7Stellar Contamination Correction Using Back-to-back Transits of TRAPPIST-1 b and cAlexander D. Rathcke0https://orcid.org/0000-0002-4227-4953Lars A. Buchhave1https://orcid.org/0000-0003-1605-5666Julien de Wit2https://orcid.org/0000-0003-2415-2191Benjamin V. Rackham3https://orcid.org/0000-0002-3627-1676Prune C. August4https://orcid.org/0000-0003-3829-8554Hannah Diamond-Lowe5https://orcid.org/0000-0001-8274-6639João M. MendonÇa6https://orcid.org/0000-0002-6907-4476Aaron Bello-Arufe7https://orcid.org/0000-0003-3355-1223Mercedes López-Morales8https://orcid.org/0000-0003-3204-8183Daniel Kitzmann9https://orcid.org/0000-0003-4269-3311Kevin Heng10https://orcid.org/0000-0003-1907-5910Department of Space Research and Space Technology, Technical University of Denmark , Elektrovej 328, 2800 Kgs. Lyngby, Denmark ; rathcke@space.dtu.dkDepartment of Space Research and Space Technology, Technical University of Denmark , Elektrovej 328, 2800 Kgs. Lyngby, Denmark ; rathcke@space.dtu.dkDepartment of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology , 77 Massachusetts Ave., Cambridge, MA 02139, USA; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology , Cambridge, MA 02139, USADepartment of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology , 77 Massachusetts Ave., Cambridge, MA 02139, USA; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology , Cambridge, MA 02139, USADepartment of Space Research and Space Technology, Technical University of Denmark , Elektrovej 328, 2800 Kgs. Lyngby, Denmark ; rathcke@space.dtu.dkDepartment of Space Research and Space Technology, Technical University of Denmark , Elektrovej 328, 2800 Kgs. Lyngby, Denmark ; rathcke@space.dtu.dk; Space Telescope Science Institute , 3700 San Martin Dr., Baltimore, MD 21218, USADepartment of Space Research and Space Technology, Technical University of Denmark , Elektrovej 328, 2800 Kgs. Lyngby, Denmark ; rathcke@space.dtu.dk; Department of Physics and Astronomy, University of Southampton , Highfield, Southampton SO17 1BJ, UK; School of Ocean and Earth Science, University of Southampton , Southampton SO14 3ZH, UKDepartment of Space Research and Space Technology, Technical University of Denmark , Elektrovej 328, 2800 Kgs. Lyngby, Denmark ; rathcke@space.dtu.dk; Jet Propulsion Laboratory , California Institute of Technology, Pasadena, CA 91109, USASpace Telescope Science Institute , 3700 San Martin Dr., Baltimore, MD 21218, USASpace Research and Planetary Sciences, Physics Institute, University of Bern , Gesellschaftsstrasse 6, 3012 Bern, Switzerland; Center for Space and Habitability, University of Bern , Gesellschaftsstrasse 6, 3012 Bern, SwitzerlandLudwig Maximilian University , Faculty of Physics, University Observatory, Scheinerstr. 1, Munich D-81679, Germany; ARTORG Center for Biomedical Engineering Research, University of Bern , Murtenstrasse 50, CH-3008 Bern, Switzerland; University College London , Department of Physics & Astronomy, Gower St., London WC1E 6BT, UK; University of Warwick , Department of Physics, Astronomy & Astrophysics Group, Coventry CV4 7AL, UKStellar surface heterogeneities, such as spots and faculae, often contaminate exoplanet transit spectra, hindering precise atmospheric characterization. We demonstrate a novel, epoch-based, model-independent method to mitigate stellar contamination, applicable to multiplanet systems with at least one airless planet. We apply this method using quasi-simultaneous transits of TRAPPIST-1 b and TRAPPIST-1 c observed on 2024 July 9, with JWST/NIRSpec PRISM. These two planets, with nearly identical radii and impact parameters, are likely to either be bare rocks or possess thin, low-pressure atmospheres, making them ideal candidates for this technique, as variations in their transit spectra would be primarily attributed to stellar activity. Our observations reveal their transit spectra exhibit consistent features, indicating similar levels of stellar contamination. We use TRAPPIST-1 b to correct the transit spectrum of TRAPPIST-1 c, achieving a 2.5 × reduction in stellar contamination at shorter wavelengths. At longer wavelengths, lower signal-to-noise ratio prevents clear detection of contamination or full assessment of mitigation. Still, out-of-transit analysis reveals variations across the spectrum, suggesting contamination extends into the longer wavelengths. Based on the success of the correction at shorter wavelengths, we argue that contamination is also reduced at longer wavelengths to a similar extent. This shifts the challenge of detecting atmospheric features to a predominantly white noise issue, which can be addressed by stacking observations. This method enables epoch-specific stellar contamination corrections, allowing coaddition of planetary spectra for reliable searches of secondary atmospheres with signals of 60–250 ppm. Additionally, we identify small-scale cold (∼2000 K) and warm (∼2600 K) regions almost uniformly distributed on TRAPPIST-1, with overall covering fractions varying by ∼0.1% per hour.https://doi.org/10.3847/2041-8213/ada5c7Transmission spectroscopyStellar atmospheresPlanet hosting starsExoplanet atmospheresFundamental parameters of starsStarspots |
| spellingShingle | Alexander D. Rathcke Lars A. Buchhave Julien de Wit Benjamin V. Rackham Prune C. August Hannah Diamond-Lowe João M. MendonÇa Aaron Bello-Arufe Mercedes López-Morales Daniel Kitzmann Kevin Heng Stellar Contamination Correction Using Back-to-back Transits of TRAPPIST-1 b and c The Astrophysical Journal Letters Transmission spectroscopy Stellar atmospheres Planet hosting stars Exoplanet atmospheres Fundamental parameters of stars Starspots |
| title | Stellar Contamination Correction Using Back-to-back Transits of TRAPPIST-1 b and c |
| title_full | Stellar Contamination Correction Using Back-to-back Transits of TRAPPIST-1 b and c |
| title_fullStr | Stellar Contamination Correction Using Back-to-back Transits of TRAPPIST-1 b and c |
| title_full_unstemmed | Stellar Contamination Correction Using Back-to-back Transits of TRAPPIST-1 b and c |
| title_short | Stellar Contamination Correction Using Back-to-back Transits of TRAPPIST-1 b and c |
| title_sort | stellar contamination correction using back to back transits of trappist 1 b and c |
| topic | Transmission spectroscopy Stellar atmospheres Planet hosting stars Exoplanet atmospheres Fundamental parameters of stars Starspots |
| url | https://doi.org/10.3847/2041-8213/ada5c7 |
| work_keys_str_mv | AT alexanderdrathcke stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc AT larsabuchhave stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc AT juliendewit stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc AT benjaminvrackham stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc AT prunecaugust stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc AT hannahdiamondlowe stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc AT joaommendonca stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc AT aaronbelloarufe stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc AT mercedeslopezmorales stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc AT danielkitzmann stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc AT kevinheng stellarcontaminationcorrectionusingbacktobacktransitsoftrappist1bandc |