J/A+A/708/A302ivo://CDS.VizieR/J/A+A/708/A302CDSPoyatos J.Fors O.Gomez Cama J.M.2026-05-04T07:43:19Z2026-04-20T08:43:21ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frm-starsstellar-flaresphotometryvisible-astronomyStellar flares are intense bursts of radiation caused by magnetic reconnection events on active stars. They are especially frequent on M dwarfs, where they can significantly influence the habitability of orbiting planets. Flare frequency distributions (FFDs) are typically modelled as power laws. However, recent studies have challenged this assumption, proposing alternative distributions such as lognormal laws that imply different flare generation mechanisms and levels of planetary impact. This study investigates which statistical distribution best describes flare occurrences on M dwarfs, considering both equivalent duration (ED), the quantity directly measured from light curve photometry, and bolometric energy, which is relevant for physical interpretations and habitability assessments. We analysed 110 M dwarfs observed with TESS and CHEOPS, detecting 5,620 flares. We decomposed complex flare events, corrected for detection biases in recovery rate and energy estimation, and scaled the FFDs from both missions to build a combined distribution covering 6 orders of magnitude in bolometric energy. We find that ED-based FFDs closely follow a power-law distribution, reflecting the intrinsic photometric flare occurrence. However, bolometric energy-based FFDs deviate significantly from a pure power law. These are better described by a lognormal distribution, although the best fit is achieved with a truncated power law, exhibiting a break at 1.8x10^35^erg. Using right-tail stabilised Kolmogorov-Smirnov and exceedance tests, we attribute this deviation to limited sampling of the most energetic events. Our results show that the low-energy flattening, previously interpreted as for lognormal behaviour, arises from observational biases and can be corrected through flare injection-recovery and the combination of observations from instruments with different sensitivities. We also find that current instruments are unable to reliably sample flares above 10^35 erg, which are the most relevant for exoplanetary atmospheric effects. The upcoming PLATO mission will be able to investigate both regimes.2026A&A...708A.302Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/708/A302CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/708/A302https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/708/A302http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/708/A302https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/708/A302https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/708/A302http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/708/A302GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/708/A302/tablea1 (List of studied stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/708/A302/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/708/A302/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/708/A302/tablea1?GETtext/xml+votable180.050000true55.405322255.21856420.0055555555555555566/131 307 546 1845 1875 1896 1911 2737 2747 3031 3163 3715 4104 4444 5420 5488 5677 6346 6384 6552 6672 6883 7264 7940 8440 8733 8739 9359 10303 10683 13512 13688 13743 13875 13912 16391 16758 18195 18496 18666 19064 19466 19668 20071 20100 20131 20311 20896 21171 21748 21953 22040 22309 22645 22807 23564 23735 23765 23793 24227 24713 25528 25989 26555 26560 26583 26821 26972 27141 27201 27204 27289 27459 28223 28279 28343 28494 28548 28646 29684 30200 30429 30505 30625 30771 30833 30893 31014 31781 32052 32089 32115 32319 32335 32491 36526 37942 38551 40513 41591 42101 42290 42652 44379 44921 46598 46632 48263 48274 49101https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/708/A302?format=asciiOpticaldefaultJ/A+A/708/A302/tablea1List of studied starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTargetTarget namemeta.id;meta.maincharTICTIC identifiermeta.idSpTypeSpectral typesrc.spTypecharGmagG magnitudemagphot.mag;em.optfloatTeffEffective temperatureKphys.temperature.effectivefloatDistDistancepcpos.distancefloatRadiusRadiussolRadphys.angSize;srcfloatvsini? Rotational velocitykm/sphys.veloc.rotatfloatnullableTESSobsTime? TESS observation timedtime.epochfloatnullableCHEOPSobsTimeCHEOPS observation timedtime.epochfloatTESSflares? Number of TESS flaresmeta.numberintnullableCHEOPSflares? Number of CHEOPS flaresmeta.numberintnullableSimbadSimbad column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main