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Discovering planets with PLATO: Comparison of algorithms for stellar activity filtering

Canocchi, G. and Malavolta, L. and Pagano, I. and Barragan, Oscar and Piotto, G and Aigrain, S. and Desidera, S. and Grziwa, S. and Cabrera Perez, Juan and Rauer, Heike (2023) Discovering planets with PLATO: Comparison of algorithms for stellar activity filtering. Astronomy & Astrophysics, 672, A144. EDP Sciences. doi: 10.1051/0004-6361/202244067. ISSN 0004-6361.

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Official URL: https://www.aanda.org/articles/aa/full_html/2023/04/aa44067-22/aa44067-22.html


Context. To date, stellar activity is one of the main limitations in detecting small exoplanets via the transit photometry technique. Since this activity is enhanced in young stars, traditional filtering algorithms may severely underperform in attempting to detect such exoplanets, with shallow transits often obscured by the photometric modulation of the light curve. Aims: This paper aims to compare the relative performances of four algorithms developed by independent research groups specifically for the filtering of activity in the light curves of young active stars, prior to the search for planetary transit signals: Notch and LOCoR (N&L), Young Stars Detrending (YSD), K2 Systematics Correction (K2SC), and VARLET. Our comparison also includes the two best-performing algorithms implemented in the Wōtan package: Tukey's biweight and Huber spline algorithms. Methods: For this purpose, we performed a series of injection-retrieval tests of planetary transits of different types, from Jupiter down to Earth-sized planets, moving both on circular and eccentric orbits. These experiments were carried out over a set of 100 realistically simulated light curves of both quiet and active solar-like stars (i.e., F and G types) that will be observed by the ESA Planetary Transits and Oscillations of stars (PLATO) space telescope, starting 2026. Results: From the experiments for transit detections, we found that N&L is the best choice in many cases, since it misses the lowest number of transits. However, this algorithm is shown to underperform when the planetary orbital period closely matches the stellar rotation period, especially in the case of small planets for which the biweight and VARLET algorithms work better. Moreover, for light curves with a large number of data-points, the combined results of two algorithms, YSD and Huber spline, yield the highest recovery percentage. Filtering algorithms allow us to obtain a very precise estimate of the orbital period and the mid-transit time of the detected planets, while the planet-to-star radius is underestimated most of the time, especially in cases of grazing transits or eccentric orbits. A refined filtering that takes into account the presence of the planet is thus compulsory for proper planetary characterization analyses.

Item URL in elib:https://elib.dlr.de/196586/
Document Type:Article
Title:Discovering planets with PLATO: Comparison of algorithms for stellar activity filtering
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Canocchi, G.Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91, Stockholm, Sweden ; Dipartimento di Fisica e Astronomia "Galileo Galilei" - Università di Padova, Vicolo dell'Osservatorio 3, 35122, Padova, ItalyUNSPECIFIEDUNSPECIFIED
Malavolta, L.INAF, Osservatorio Astronomico di Padova, Padova, ItalyUNSPECIFIEDUNSPECIFIED
Pagano, I.INAF – Osservatorio Astrofisico di Catania, Via S.Sofia 78, 95123 Catania, ItalyUNSPECIFIEDUNSPECIFIED
Barragan, OscarOxford Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UKUNSPECIFIEDUNSPECIFIED
Piotto, GDipartimento di Fisica e Astronomia, Universitá di Padova, Padova, ItalyUNSPECIFIEDUNSPECIFIED
Aigrain, S.Department of Physics, Denys Wilkinson Building Keble Road, Oxford, OX1 3RHUNSPECIFIEDUNSPECIFIED
Desidera, S.INAF - Osservatorio Astronomico di Padova, ItalyUNSPECIFIEDUNSPECIFIED
Grziwa, S.Rheinisches Institut furr Umweltforschung an der Universitaet zu Koeln, Aachener Strasse 209, 50931 Koeln, GermanyUNSPECIFIEDUNSPECIFIED
Cabrera Perez, JuanUNSPECIFIEDhttps://orcid.org/0000-0001-6653-5487UNSPECIFIED
Rauer, HeikeUNSPECIFIEDhttps://orcid.org/0000-0002-6510-1828UNSPECIFIED
Date:14 April 2023
Journal or Publication Title:Astronomy & Astrophysics
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:A144
Publisher:EDP Sciences
Keywords:planets and satellites: detection; techniques: photometric; methods: data analysis; stars: activity; planetary systems; Astrophysics - Earth and Planetary Astrophysics; Astrophysics - Instrumentation and Methods for Astrophysics
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
DLR - Research theme (Project):R - Project PLATO - PMC and Science
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Extrasolar Planets and Atmospheres
Institute of Planetary Research > Leitungsbereich PF
Deposited By: Cabrera Perez, Juan
Deposited On:28 Aug 2023 09:17
Last Modified:04 Dec 2023 11:21

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