methods: data analysis; planetary systems; stars: activity; stars: flare; techniques: photometric; Cool stars; Exo-planets; Methods. Data analysis; Parameter distributions; Photometrics; Planetary system; Star: activity; Stars: flare; Techniques: photometric; White light; Astronomy and Astrophysics; Space and Planetary Science
Abstract :
[en] Context. White-light stellar flares are proxies for some of the most energetic types of flares, but their triggering mechanism is still poorly understood. As they are associated with strong X and ultraviolet emission, their study is particularly relevant to estimate the amount of high-energy irradiation onto the atmospheres of exoplanets, especially those in their stars’ habitable zone. Aims. We used the high-cadence, high-photometric capabilities of the CHEOPS and TESS space telescopes to study the detailed morphology of white-light flares occurring in a sample of 130 late-K and M stars, and compared our findings with results obtained at a lower cadence. Methods. We employed dedicated software for the reduction of 3 s cadence CHEOPS data, and adopted the 20 s cadence TESS data reduced by their official processing pipeline. We developed an algorithm to separate multi-peak flare profiles into their components, in order to contrast them to those of single-peak, classical flares. We also exploited this tool to estimate amplitudes and periodicities in a small sample of quasi-periodic pulsation (QPP) candidates. Results. Complex flares represent a significant percentage (≳30%) of the detected outburst events. Our findings suggest that high-impulse flares are more frequent than suspected from lower-cadence data, so that the most impactful flux levels that hit close-in exoplanets might be more time-limited than expected. We found significant differences in the duration distributions of single and complex flare components, but not in their peak luminosity. A statistical analysis of the flare parameter distributions provides marginal support for their description with a log-normal instead of a power-law function, leaving the door open to several flare formation scenarios. We tentatively confirmed previous results about QPPs in high-cadence photometry, report the possible detection of a pre-flare dip, and did not find hints of photometric variability due to an undetected flare background. Conclusions. The high-cadence study of stellar hosts might be crucial to evaluate the impact of their flares on close-in exoplanets, as their impulsive phase emission might otherwise be incorrectly estimated. Future telescopes such as PLATO and Ariel, thanks to their high-cadence capability, will help in this respect. As the details of flare profiles and of the shape of their parameter distributions are made more accessible by continuing to increase the instrument precision and time resolution, the models used to interpret them and their role in star-planet interactions might need to be updated constantly.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Bruno, G. ; INAF, Osservatorio Astrofisico di Catania, Catania, Italy
Pagano, I. ; INAF, Osservatorio Astrofisico di Catania, Catania, Italy
Scandariato, G. ; INAF, Osservatorio Astrofisico di Catania, Catania, Italy
Florén, H.-G. ; Department of Astronomy, Stockholm University, AlbaNova University Center, Stockholm, Sweden
Brandeker, A. ; Department of Astronomy, Stockholm University, AlbaNova University Center, Stockholm, Sweden
Olofsson, G. ; Department of Astronomy, Stockholm University, AlbaNova University Center, Stockholm, Sweden
Maxted, P.F.L. ; Astrophysics Group, Lennard Jones Building, Keele University, Staffordshire, United Kingdom
Fortier, A. ; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Sousa, S.G. ; Instituto de Astrofisica e Ciencias do Espaco, Universidade do Porto, CAUP, Porto, Portugal
Sulis, S. ; Aix Marseille Univ., CNRS, CNES, LAM, Marseille, France
Van Grootel, Valérie ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Garai, Z. ; HUN-REN-ELTE Exoplanet Research Group, Szombathely, Hungary ; ELTE Gothard Astrophysical Observatory, Szombathely, Hungary ; Astronomical Institute, Slovak Academy of Sciences, Tatranská Lomnica, Slovakia
Boldog, A. ; HUN-REN-ELTE Exoplanet Research Group, Szombathely, Hungary ; Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, Budapest, Hungary ; CSFK, MTA Centre of Excellence, Budapest, Hungary
Kriskovics, L.; Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, Budapest, Hungary ; CSFK, MTA Centre of Excellence, Budapest, Hungary
Gandolfi, D. ; Dipartimento di Fisica, Università degli Studi di Torino, Torino, Italy
Alibert, Y. ; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Alonso, R. ; Instituto de Astrofísica de Canarias, La Laguna, Spain ; Departamento de Astrofísica, Universidad de La Laguna, La Laguna, Spain
Bárczy, T. ; Admatis, Miskolc, Hungary
Barrado Navascues, D. ; Depto. de Astrofísica, Centro de Astrobiología (CSIC-INTA), Madrid, Spain
Barros, S.C.C. ; Instituto de Astrofisica e Ciencias do Espaco, Universidade do Porto, CAUP, Porto, Portugal ; Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Porto, Portugal
Baumjohann, W. ; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Beck, M. ; Observatoire astronomique de l’Université de Genève, Versoix, Switzerland
Beck, T. ; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Bern, Switzerland
Benz, W. ; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Billot, N. ; Observatoire astronomique de l’Université de Genève, Versoix, Switzerland
Borsato, L. ; INAF, Osservatorio Astronomico di Padova, Padova, Italy
Broeg, C. ; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Collier Cameron, A. ; Centre for Exoplanet Science, SUPA School of Physics and Astronomy, University of St Andrews, St Andrews, United Kingdom
Csizmadia, Sz. ; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany
Cubillos, P.E.; Space Research Institute, Austrian Academy of Sciences, Graz, Austria ; INAF, Osservatorio Astrofisico di Torino, Pino Torinese To, Italy
Davies, M.B. ; Centre for Mathematical Sciences, Lund University, Lund, Sweden
Deleuil, M. ; Aix Marseille Univ., CNRS, CNES, LAM, Marseille, France
Deline, A.; Observatoire astronomique de l’Université de Genève, Versoix, Switzerland
Delrez, L. ; Space sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, Liège, Belgium ; Astrobiology Research Unit, Université de Liège, Liège, Belgium ; Institute of Astronomy, KU Leuven, Leuven, Belgium
Demangeon, O.D.S. ; Instituto de Astrofisica e Ciencias do Espaco, Universidade do Porto, CAUP, Porto, Portugal ; Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Porto, Portugal
Demory, B.-O. ; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Ehrenreich, D. ; Observatoire astronomique de l’Université de Genève, Versoix, Switzerland ; Centre Vie dans l’Univers, Faculté des sciences, Université de Genève, Genève 4, Switzerland
Erikson, A.; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany
Farinato, J.; INAF, Osservatorio Astronomico di Padova, Padova, Italy
Fossati, L. ; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Fridlund, M. ; Leiden Observatory, University of Leiden, Leiden, Netherlands ; Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
Gillon, Michaël ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO)
Güdel, M. ; Department of Astrophysics, University of Vienna, Vienna, Austria
Günther, M.N. ; European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands
Heitzmann, A. ; Observatoire astronomique de l’Université de Genève, Versoix, Switzerland
Helling, Ch.; Space Research Institute, Austrian Academy of Sciences, Graz, Austria ; Institute for Theoretical Physics and Computational Physics, Graz University of Technology, Graz, Austria
Hoyer, S. ; Aix Marseille Univ., CNRS, CNES, LAM, Marseille, France
Isaak, K.G. ; European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands
Kiss, L.L. ; Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Budapest, Hungary ; ELTE Institute of Physics, Pázmány Péter sétány 1/A, Budapest, Hungary
Lam, K.W.F. ; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany
Laskar, J. ; IMCCE, UMR8028 CNRS, Observatoire de Paris, PSL Univ., Sorbonne Univ., Paris, France
Lecavelier des Etangs, A. ; Institut d’astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, Paris, France
Lendl, M. ; Observatoire astronomique de l’Université de Genève, Versoix, Switzerland
Magrin, D. ; INAF, Osservatorio Astronomico di Padova, Padova, Italy
Mordasini, C. ; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Nascimbeni, V. ; INAF, Osservatorio Astronomico di Padova, Padova, Italy
Ottensamer, R.; Department of Astrophysics, University of Vienna, Vienna, Austria
Pallé, E. ; Instituto de Astrofísica de Canarias, La Laguna, Spain ; Departamento de Astrofísica, Universidad de La Laguna, La Laguna, Spain
Peter, G. ; Institute of Optical Sensor Systems, German Aerospace Center (DLR), Berlin, Germany
Piotto, G. ; INAF, Osservatorio Astronomico di Padova, Padova, Italy ; Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università degli Studi di Padova, Padova, Italy
Pollacco, D.; Department of Physics, University of Warwick, Coventry, United Kingdom
Queloz, D. ; ETH Zurich, Department of Physics, Zurich, Switzerland ; Cavendish Laboratory, Cambridge, United Kingdom
Ragazzoni, R. ; INAF, Osservatorio Astronomico di Padova, Padova, Italy ; Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università degli Studi di Padova, Padova, Italy
Rando, N.; European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands
Ratti, F.; European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands
Rauer, H. ; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany ; Institut fuer Geologische Wissenschaften, Freie Universitaet Berlin, Berlin, Germany
Ribas, I. ; Institut de Ciencies de l’Espai (ICE, CSIC), Bellaterra, Spain ; Institut d’Estudis Espacials de Catalunya (IEEC), Barcelona, Spain
Santos, N.C. ; Instituto de Astrofisica e Ciencias do Espaco, Universidade do Porto, CAUP, Porto, Portugal ; Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Porto, Portugal
Sarajlic, M.; Astrophysics Group, Lennard Jones Building, Keele University, Staffordshire, United Kingdom
Ségransan, D. ; Observatoire astronomique de l’Université de Genève, Versoix, Switzerland
Simon, A.E. ; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Singh, V. ; INAF, Osservatorio Astrofisico di Catania, Catania, Italy
Smith, A.M.S. ; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany
Stalport, Manu ; Université de Liège - ULiège > Unités de recherche interfacultaires > Space sciences, Technologies and Astrophysics Research (STAR)
Thomas, N.; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Bern, Switzerland
Udry, S. ; Observatoire astronomique de l’Université de Genève, Versoix, Switzerland
Ulmer, B.; Institute of Optical Sensor Systems, German Aerospace Center (DLR), Berlin, Germany
Venturini, J. ; Observatoire astronomique de l’Université de Genève, Versoix, Switzerland
Villaver, E.; Instituto de Astrofísica de Canarias, La Laguna, Spain ; Departamento de Astrofísica, Universidad de La Laguna, La Laguna, Spain
Walton, N.A. ; Institute of Astronomy, University of Cambridge, Cambridge, United Kingdom
Wilson, T.G. ; Department of Physics, University of Warwick, Coventry, United Kingdom
We thank Antonino F. Lanza and Daniel Brito de Freitas for their suggestions and the very fruitful discussions we had. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. Our search was helped by the use of the ASTROQUERY package (Ginsburg et al. 2019). CHEOPS is an ESA mission in partnership with Switzerland with important contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom. The CHEOPS Consortium would like to gratefully acknowledge the support received by all the agencies, offices, universities, and industries involved. Their flexibility and willingness to explore new approaches were essential to the success of this mission. CHEOPS data analysed in this article will be made available in the CHEOPS mission archive ( https://cheops.unige.ch/archive_browser/ ). L.B., G.B., V.N., I.P., G.P., R.R., and G.S. acknowledge support from CHEOPS ASI-INAF agreement n. 2019-29-HH.0. A.B. was supported by the SNSA. P.M. acknowledges support from STFC research grant number ST/R000638/1. S.G.S. acknowledges support from FCT through FCT contract nr. CEECIND/00826/2018 and POPH/FSE (EC). The Portuguese team thanks the Portuguese Space Agency for the provision of financial support in the framework of the PRODEX Programme of the European Space Agency (ESA) under contract number 4000142255. V.V.G. is an F.R.S-FNRS Research Associate. Z.G. was supported by the VEGA grant of the Slovak Academy of Sciences No. 2/0031/22 and by the Slovak Research and Development Agency \u2013 the contract No. APVV-20-0148. G.M.S. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, a PRODEX Experiment Agreement No. 4000137122, the Lend\u00FClet LP2018-7/2021 grant of the Hungarian Academy of Science and the support of the city of Szombathely. D.G. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 \u201CGaseousor rocky? Unveiling the nature of small worlds\u201D. Y.Al. acknowledges support from the Swiss National Science Foundation (SNSF) under grant 200020_192038. We acknowledge financial support from the Agencia Estatal de Investigaci\u00F3n of the Ministerio de Ciencia e Innovaci\u00F3n MCIN/AEI/10.13039/501100011033 and the ERDF \u201CA way of making Europe\u201D through projects PID2019-107061GB-C61, PID2019-107061GB-C66, PID2021-125627OB-C31, and PID2021-125627OB-C32, from the Centre of Excellence \u201CSevero Ochoa\u201D award to the Instituto de Astrof\u00EDsica de Canarias (CEX2019-000920-S), from the Centre of Excellence \u201CMar\u00EDa de Maeztu\u201D award to the Institut de Ci\u00E8ncies de l\u2019Espai (CEX2020-001058-M), and from the Generalitat de Catalunya/CERCA programme. We acknowledge financial support from the Agencia Estatal de Investigaci\u00F3n of the Ministerio de Ciencia e Innovaci\u00F3n MCIN/AEI/10.13039/501100011033 and the ERDF \u201CA way of making Europe\u201D through projects PID2019-107061GB-C61, PID2019-107061GB-C66, PID2021-125627OB-C31, and PID2021-125627OB-C32, from the Centre of Excellence \u201CSevero Ochoa\u201D award to the Instituto de Astrof\u00EDsica de Canarias (CEX2019-000920-S), from the Centre of Excellence \u201CMar\u00EDa de Maeztu\u201D award to the Institut de Ci\u00E8ncies de l\u2019Espai (CEX2020-001058-M), and from the Generalitat de Catalunya/CERCA programme. S.C.C.B. acknowledges support from FCT through FCT contracts nr. IF/01312/2014/CP1215/CT0004. C.B. acknowledges support from the Swiss Space Office through the ESA PRODEX program. This work has been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grants 51NF40_182901 and 51NF40_205606. A.C.C. acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. P.E.C. is funded by the Austrian Science Fund (FWF) Erwin Schroedinger Fellowship, program J4595-N. This project was supported by the CNES. S.S. acknowledges support from CNES, the Programme National de Plan\u00E9tologie (PNP), and the Programme National de Physique Stellaire (PNPS) of CNRS-INSU. The Belgian participation to CHEOPS has been supported by the Belgian Federal Science Policy Office (BELSPO) in the framework of the PRODEX Program, and by the University of Li\u00E8ge through an ARC grant for Concerted Research Actions financed by the Wallonia-Brussels Federation. L.D. thanks the Belgian Federal Science Policy Office (BELSPO) for the provision of financial support in the framework of the PRODEX Programme of the European Space Agency (ESA) under contract number 4000142531. This work was supported by FCT \u2013 Funda\u00E7\u00E3o para a Ci\u00EAncia e a Tecnologia through national funds and by FEDER through COMPETE2020 through the research grants UIDB/04434/2020, UIDP/04434/2020, 2022.06962.PTDC. O.D.S.D. is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. B.-O.D. acknowledges support from the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number MB22.00046. This project has received funding from the Swiss National Science Foundation for project 200021_200726. It has also been carried out within the framework of the National Centre of Competence in Research PlanetS supported by the Swiss National Science Foundation under grant 51NF40_205606. The authors acknowledge the financial support of the SNSF. M.F. and C.M.P. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19, 174/18). M.G. is an F.R.S.-FNRS Senior Research Associate. M.N.G. is the ESA CHEOPS Project Scientist and Mission Representative, and as such also responsible for the Guest Observers (GO) Programme. MNG does not relay proprietary information between the GO and Guaranteed Time Observation (GTO) Programmes, and does not decide on the definition and target selection of the GTO Programme. C.He. acknowledges support from the European Union H2020-MSCA-ITN-2019 under Grant Agreement no. 860470 (CHAMELEON). S.H. gratefully acknowledges CNES funding through the grant 837319. K.G.I. is the ESA CHEOPS Project Scientist and is responsible for the ESA CHEOPS Guest Observers Programme. She does not participate in, or contribute to, the definition of the Guaranteed Time Programme of the CHEOPS mission through which observations described in this paper have been taken, nor to any aspect of target selection for the programme. K.W.F.L. was supported by Deutsche Forschungsgemeinschaft grants RA714/14-1 within the DFG Schwerpunkt SPP 1992, Exploring the Diversity of Extrasolar Planets. This work was granted access to the HPC resources of MesoPSL financed by the Region Ile de France and the project Equip@Meso (reference ANR-10-EQPX-29-01) of the programme Investissements d\u2019Avenir supervised by the Agence Nationale pour la Recherche. M.L. acknowledges support of the Swiss National Science Foundation under grant number PCEFP2_194576. This work was also partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). N.C.S. acknowledges funding by the European Union (ERC, FIERCE, 101052347). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. A.S. acknowledges support from the Swiss Space Office through the ESA PRODEX program. J.V. acknowledges support from the Swiss National Science Foundation (SNSF) under grant PZ00P2_208945. N.A.W. acknowledges UKSA grant ST/R004838/1. T.W. acknowledges support from the UKSA and the University of Warwick.
