Euclid Quick Data Release (Q1)
Astronomy and Astrophysics, vol. 711, pp. A32
Abstract
In the era of large-scale surveys such as Euclid , machine learning has become an essential tool for identifying rare yet scientifically valuable objects, such as strong gravitational lenses. However, supervised machine-learning approaches require large quantities of labelled examples to train on, and the limited number of known strong lenses has led to a reliance on simulations for training. A well-known challenge is that machine-learning models trained on one data domain often underperform when applied to a different domain: in the context of lens finding, this means that strong performance on simulated lenses does not necessarily translate into equally good performance on real observations. In the Euclid Quick Data Release 1 (Q1), covering 63 deg 2 , 500 strong lens candidates were discovered through a synergy of machine learning, citizen science, and expert visual inspection. These discoveries now allow us to quantify this performance gap and investigate the impact of training on real data. We find that a network trained only on simulations recovers up to 92% of simulated lenses with 100% purity, but only achieves 50% completeness with 24% purity on real Euclid data. By augmenting training data with real Euclid lenses and non-lenses, completeness improves by 25–30% in terms of the expected yield of discoverable lenses in the Euclid Data Release 1 and the full Euclid Wide Survey. Roughly 20% of this improvement comes from the inclusion of real lenses in the training data, while 5–10% comes from exposure to a more diverse set of non-lenses and false positives from Q1. We show that the most effective lens-finding strategy for real-world performance combines the diversity of simulations with the fidelity of real lenses. This hybrid approach establishes a clear methodology for maximising lens discoveries in future data releases from Euclid and will likely also be applicable to other surveys such as the Vera Rubin Observatory’s Legacy Survey of Space and Time.
Authors 96
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Affiliation as printed
Institute of Cosmology and Gravitation, University of Portsmouth
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Affiliation as printed
Institute of Cosmology and Gravitation, University of Portsmouth
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Affiliation as printed
Institute of Cosmology and Gravitation, University of Portsmouth
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FHNW University of Applied Sciences and Arts Northwestern Switzerland
Affiliation as printed
University of Applied Sciences and Arts of Northwestern Switzerland, School of Computer Science
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University of Milan · National Institute for Astrophysics
Affiliation as printed
Dipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano
INAF-IASF Milano
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics · University of Bologna
Affiliation as printed
Dipartimento di Fisica e Astronomia “Augusto Righi” – Alma Mater Studiorum Università di Bologna
INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
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Affiliation as printed
Institute of Cosmology and Gravitation, University of Portsmouth
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Affiliation as printed
Department of Physics, Oxford University
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Istituto Nazionale di Fisica Nucleare, Sezione di Bologna · Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics · University of Bologna
Affiliation as printed
Dipartimento di Fisica e Astronomia “Augusto Righi” – Alma Mater Studiorum Università di Bologna
INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
INFN-Sezione di Bologna
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Institució Catalana de Recerca i Estudis Avançats · Institute of Space Sciences · Consejo Superior de Investigaciones Científicas · Institut de Ciències del Cosmos · Universitat de Barcelona
Affiliation as printed
Institució Catalana de Recerca i Estudis Avançats (ICREA)
Institut de Ciencies de l’Espai (IEEC-CSIC), Campus UAB
Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (IEEC-UB)
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Centre National de la Recherche Scientifique · Aix-Marseille Université · Institut d'Astrophysique de Paris · Sorbonne Université
Affiliation as printed
Aix-Marseille Université, CNRS, CNES, LAM
Institut d’Astrophysique de Paris, UMR 7095, CNRS, and Sorbonne Université
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Astronomical Observatory of Capodimonte · National Institute for Astrophysics
Affiliation as printed
INAF-Osservatorio Astronomico di Capodimonte
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École Polytechnique Fédérale de Lausanne
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Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny
SCITAS, Ecole Polytechnique Fédérale de Lausanne (EPFL)
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Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale
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Université Paris-Saclay, CNRS, Institut d’astrophysique spatiale
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European Space Agency · European Space Astronomy Centre
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ESAC/ESA
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Institut für Theoretische Physik, University of Heidelberg
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Brera Astronomical Observatory · National Institute for Astrophysics
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INAF-Osservatorio Astronomico di Brera
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
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Scuola Internazionale Superiore di Studi Avanzati · Trieste Astronomical Observatory · Istituto Nazionale di Fisica Nucleare, Sezione di Trieste · Institute for Fundamental Physics of the Universe · National Institute for Astrophysics
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IFPU, Institute for Fundamental Physics of the Universe
INAF-Osservatorio Astronomico di Trieste
INFN, Sezione di Trieste
SISSA, International School for Advanced Studies
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Istituto Nazionale di Fisica Nucleare, Sezione di Bologna · Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics · University of Bologna
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Dipartimento di Fisica e Astronomia, Università di Bologna
INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
INFN-Sezione di Bologna
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Osservatorio Astronomico di Padova · National Institute for Astrophysics
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
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Trieste Astronomical Observatory · Institute for Fundamental Physics of the Universe · National Institute for Astrophysics
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IFPU, Institute for Fundamental Physics of the Universe
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Brera Astronomical Observatory · Istituto Nazionale di Fisica Nucleare, Sezione di Genova · University of Genoa · National Institute for Astrophysics
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Dipartimento di Fisica, Università di Genova
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INFN-Sezione di Genova
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Astronomical Observatory of Capodimonte · University of Naples Federico II · National Institute for Astrophysics
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Department of Physics “E. Pancini”, University Federico II
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Istituto Nazionale di Fisica Nucleare, Sezione di Torino · Osservatorio Astrofisico di Torino · University of Turin · National Institute for Astrophysics
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Dipartimento di Fisica, Università degli Studi di Torino
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Leiden University · Royal Observatory · Leiden Observatory · University of Edinburgh
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Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill
Leiden Observatory, Leiden University
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Osservatorio Astrofisico di Torino · National Institute for Astrophysics
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Universitat Autònoma de Barcelona · Port d'Informació Científica · Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
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Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT)
Port d’Informació Científica, Campus UAB
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Astronomical Observatory of Rome · National Institute for Astrophysics
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
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Istituto Nazionale di Fisica Nucleare · Astronomical Observatory of Capodimonte · Istituto Nazionale di Fisica Nucleare, Sezione di Napoli · National Institute for Astrophysics
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INFN section of Naples
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Dipartimento di Fisica e Astronomia “Augusto Righi” – Alma Mater Studiorum Università di Bologna
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Instituto de Astrofísica de Canarias
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Instituto de Astrofísica de Canarias
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Royal Observatory · University of Edinburgh
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Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester
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European Space Agency · European Space Astronomy Centre · European Space Research Institute
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Lyon 1 Université · Centre National de la Recherche Scientifique · Institut National de Physique Nucléaire et de Physique des Particules · Institut de Physique des 2 Infinis de Lyon
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UCB Lyon 1, CNRS/IN2P3, IUF, IP2I Lyon
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Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking
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Department of Astronomy, University of Geneva
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Trieste Astronomical Observatory · National Institute for Astrophysics
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Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale
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Université Paris-Saclay, CNRS, Institut d’astrophysique spatiale
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Department of Astronomy, University of Geneva
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European Space Agency · European Space Astronomy Centre
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ESAC/ESA
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Istituto Nazionale di Fisica Nucleare · Istituto Nazionale di Fisica Nucleare, Sezione di Padova
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Lyon 1 Université · Centre National de la Recherche Scientifique · Institut National de Physique Nucléaire et de Physique des Particules · Institut de Physique des 2 Infinis de Lyon
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Centre National de la Recherche Scientifique · Aix-Marseille Université · Centre de physique des particules de Marseille · Institut National de Physique Nucléaire et de Physique des Particules
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Aix-Marseille Université, CNRS/IN2P3, CPPM
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
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Astronomical Observatory of Rome · Agenzia Spaziale Italiana · National Institute for Astrophysics
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Space Science Data Center, Italian Space Agency
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Lyon 1 Université · Centre National de la Recherche Scientifique · Institut National de Physique Nucléaire et de Physique des Particules · Institut de Physique des 2 Infinis de Lyon
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Istituto Nazionale di Fisica Nucleare, Sezione di Bologna · Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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Ludwig-Maximilians-Universität München
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Royal Observatory · University of Edinburgh
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Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill
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Istituto Nazionale di Fisica Nucleare, Sezione di Bologna · Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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Osservatorio Astronomico di Padova · National Institute for Astrophysics
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Jet Propulsion Laboratory, California Institute of Technology
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Felix Hormuth Engineering
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Technical University of Denmark
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Cosmic Dawn Center (DAWN)
Technical University of Denmark
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Max Planck Institute for Astronomy
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Aix-Marseille Université, CNRS/IN2P3, CPPM
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Jet Propulsion Laboratory, California Institute of Technology
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Lyon 1 Université · Centre National de la Recherche Scientifique · Institut National de Physique Nucléaire et de Physique des Particules · Institut de Physique des 2 Infinis de Lyon
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Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822
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Ludwig-Maximilians-Universität München
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Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München
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University of Helsinki · Helsinki Institute of Physics
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Department of Physics
Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki
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Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d'Étude de l'Univers et des Phénomènes Extrêmes
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Laboratoire d’etude de l’Univers et des phenomenes eXtremes, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS
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Osservatorio Astrofisico di Torino · National Institute for Astrophysics
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Institute of Theoretical Astrophysics, University of Oslo
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University of Helsinki · Helsinki Institute of Physics
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SKAO, Jodrell Bank, Lower Withington
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Centre de Calcul de l’IN2P3/CNRS
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University of Milan · Istituto Nazionale di Fisica Nucleare, Sezione di Milano · National Institute for Astrophysics
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Dipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano
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INFN-Sezione di Milano
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
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Trieste Astronomical Observatory · National Institute for Astrophysics
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INAF-Osservatorio Astronomico di Trieste
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FHNW University of Applied Sciences and Arts Northwestern Switzerland
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University of Applied Sciences and Arts of Northwestern Switzerland, School of Computer Science
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Affiliation as printed
Universität Bonn, Argelander-Institut für Astronomie
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Centre National de la Recherche Scientifique · Aix-Marseille Université
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Aix-Marseille Université, CNRS, CNES, LAM
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Istituto Nazionale di Fisica Nucleare, Sezione di Bologna · Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics · University of Bologna
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Dipartimento di Fisica e Astronomia “Augusto Righi” – Alma Mater Studiorum Università di Bologna
INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
INFN-Sezione di Bologna
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Affiliation as printed
Department of Physics, Institute for Computational Cosmology, Durham University
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Osservatorio di Astrofisica e Scienza dello Spazio · National Institute for Astrophysics
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INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
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Centre National de la Recherche Scientifique · Université Paris Cité · Institut National de Physique Nucléaire et de Physique des Particules · Centre Pierre Binétruy
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CNRS-UCB International Research Laboratory, Centre Pierre Binétruy, IRL2007, CPB-IN2P3
Université Paris Cité, CNRS, Astroparticule et Cosmologie
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FHNW University of Applied Sciences and Arts Northwestern Switzerland
Affiliation as printed
University of Applied Sciences and Arts of Northwestern Switzerland, School of Engineering
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Centre National de la Recherche Scientifique · Institut d'Astrophysique de Paris · Sorbonne Université
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Institut d’Astrophysique de Paris
Institut d’Astrophysique de Paris, UMR 7095, CNRS, and Sorbonne Université
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