J/A+A/708/A302 TESS flare frequency distributions with CHEOPS (Poyatos+, 2026)
Extending TESS flare frequency distributions with CHEOPS:
Power-law or lognormal?
Poyatos J., Fors O., Gomez Cama J.M.
<Astron. Astrophys. 708, A302 (2026)>
=2026A&A...708A.302P 2026A&A...708A.302P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, M-type; Stars, flare; Photometry ; Optical
Keywords: magnetic reconnection - instrumentation: photometers -
methods: data analysis - stars: flare - stars: low-mass
Abstract:
Stellar 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 1.8x1035erg. 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.
Description:
Full table of targets, stellar parameters, and flare counts.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 88 110 List of studied stars
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Target Target name
25- 34 I10 --- TIC TIC identifier
36- 38 A3 --- SpType Spectral type
40- 44 F5.2 mag Gmag G magnitude
46- 52 F7.2 K Teff Effective temperature
54- 58 F5.2 pc Dist Distance
60- 64 F5.3 Rsun Radius Radius
66- 69 F4.1 km/s vsini ? Rotational velocity
71- 76 F6.2 d TESSobsTime ? TESS observation time
78- 81 F4.2 d CHEOPSobsTime CHEOPS observation time
83- 85 I3 --- TESSflares ? Number of TESS flares
87- 88 I2 --- CHEOPSflares ? Number of CHEOPS flares
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Acknowledgements:
Julien Poyatos, julienpoyatos(at)icc.ub.edu
License: CC-BY-4.0
(End) Patricia Vannier [CDS] 13-Mar-2026