J/A+A/686/A239 Flare morphology with CHEOPS and TESS (Bruno+, 2024)
Detailed cool star flare morphology with CHEOPS and TESS.
Bruno G., Pagano I., Scandariato G., Floren H.-G., Brandeker A.,
Olofsson G., Maxted P.F.L., Fortier A., Sousa S.G., Sulis S.,
Van Grootel V., Garai Z., Boldog A., Kriskovics L., Szabo M.Gy.,
Gandolfi D., Alibert Y., Alonso R., Barczy T., Barrado Navascues D.,
Barros S.C., Baumjohann W., Beck M., Beck T., Benz W., Billot N.,
Borsato L., Broeg C., Collier Cameron A., Csizmadia Sz., Cubillos P.E.,
Davies M.B., Deleuil M., Deline A., Delrez L., Demangeon O.D.S.,
Demory B.-O., Ehrenreich D., Erikson A., Farinato J., Fossati L.,
Fridlund M., Gillon M., Guedel M., Guenther M.N., Heitzmann A., Helling C.,
Hoyer S., Isaak K.G., Kiss L., Lam K.W.F., Laskar J.,
Lecavelier des Etangs A., Lendl M., Magrin D., Mordasini C., Nascimbeni V.,
Ottensamer R., Palle E., Peter G., Piotto G., Pollacco D., Queloz D.,
Ragazzoni R., Rando N., Ratti F., Rauer H., Ribas I., Santos N.C.,
Sarajlic M., Segransan D., Simon A.E., Singh V., Smith A.M.S., Stalport M.,
Thomas N., Udry S., Ulmer B., Venturini J., Villaver E., Walton N.A.,
Wilson T.G.
<Astron. Astrophys. 686, A239 (2024)>
=2024A&A...686A.239B 2024A&A...686A.239B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, K-type ; Stars, M-type ; Stars, flare ; Photometry ;
Optical
Keywords: methods: data analysis - techniques: photometric - stars: activity -
stars: flare - planetary systems
Abstract:
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 UV 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.
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 lower cadence.
We employed dedicated software for the reduction of 3s cadence CHEOPS
data, and adopted the 20s cadence TESS data reduced by its 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.
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 concentrated 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.
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 on this aspect. As the details of flare profiles
and of the shape of their parameter distributions are made more
accessible by ever increasing instrument precision and time
resolution, the models used to interpret them and their role in
star-planet interactions might need to be updated constantly.
Description:
Raw and detrended CHEOPS imagette light curves analysed for the paper.
Unless stated otherwise, the data sets were collected for the
Guaranteed Time Observation (GTO) programme CH_PR100018 (PI I.
Pagano). Those with a (10) in the "Explanations" column were collected
for GTO programme CH_PR100010 (PI G. Szabo).
See also MAST
(https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html)
or
https://archive.stsci.edu/tess/bulk_downloads/bulk_downloads_ffi-tp-lc-dv.html
for 20-s TESS light curves referenced in the paper, for programs in
Table A.2
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
stars.dat 261 114 List of studied stars
lc/* . 128 Individual light curves
--------------------------------------------------------------------------------
Byte-by-byte Description of file: stars.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 F17.13 deg RAdeg Right ascension (J2000)
19- 35 F17.13 deg DEdeg Declination (J2000)
37- 59 A23 --- Name Star name
61- 87 A27 --- FileName1 Name fo the light curve file in subdirectory lc
89- 99 A11 --- FileName2 Name of other light curve file in
subdirectory lc for AU Mic
101-111 A11 --- FileName3 Name of other light curve file in
subdirectory lc for AU Mic
113-123 A11 --- FileName4 Name of other light curve file in
subdirectory lc for AU Mic
125-135 A11 --- FileName5 Name of other light curve file in
subdirectory lc for AU Mic
137-147 A11 --- FileName6 Name of other light curve file in
subdirectory lc for AU Mic
149-159 A11 --- FileName7 Name of other light curve file in
subdirectory lc for AU Mic
161-171 A11 --- FileName8 Name of other light curve file in
subdirectory lc for AU Mic
173-183 A11 --- FileName9 Name of other light curve file in
subdirectory lc for AU Mic
185-196 A12 --- FileName10 Name of other light curve file in
subdirectory lc for AU Mic
198-209 A12 --- FileName11 Name of other light curve file in
subdirectory lc for AU Mic
211-222 A12 --- FileName12 Name of other light curve file in
subdirectory lc for AU Mic
224-235 A12 --- FileName13 Name of other light curve file in
subdirectory lc for AU Mic
237-248 A12 --- FileName14 Name of other light curve file in
subdirectory lc for AU Mic
250-261 A12 --- FileName15 Name of other light curve file in
subdirectory lc for AU Mic
--------------------------------------------------------------------------------
Byte-by-byte Description of file: lc/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 F18.12 d MJD Time axis
20- 38 F19.17 --- FluxNorm Raw flux divided by per-visit median value
40- 63 F24.20 deg RollAngle CHEOPS roll angle
65- 84 F20.16 e-/pix background Background flux
86 I1 --- Glint [0/1] Glint flag: if 1, the visit was
affected, 0 otherwise
88-110 E23.17 --- FluxDet Flux after removal of systematics and time
trends possibly due to stellar activity
112-134 F23.21 --- e_FluxDet Uncertainty on detrended flux
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Acknowledgements:
Giovanni Bruno, giovanni.bruno(at)inaf.it
(End) Patricia Vannier [CDS] 21-Mar-2024