| Issue |
A&A
Volume 668, December 2022
|
|
|---|---|---|
| Article Number | A101 | |
| Number of page(s) | 7 | |
| Section | Stellar atmospheres | |
| DOI | https://doi.org/10.1051/0004-6361/202243789 | |
| Published online | 12 December 2022 | |
Characteristics of flares on giant stars★
1
Konkoly Observatory, Research Centre for Astronomy and Earth Sciences,
Konkoly Thege Miklós út 15-17,
1121
Budapest, Hungary
e-mail: olah@konkoly.hu
2
CSFK, MTA Centre of Excellence,
Budapest, Konkoly Thege Miklós út 15-17,
1121
Budapest, Hungary
3
Eötvös University, Department of Astronomy,
Pf. 32,
1518
Budapest, Hungary
Received:
14
April
2022
Accepted:
13
October
2022
Context. Although late-type dwarfs and giant stars are substantially different, their flares are thought to originate in similar physical processes and differ only by a scale factor in the energy levels. We study the validity of this approach.
Aims. We search for characteristics of flares on active giants, which might be statistically different from those on main-sequence stars.
Methods. We used nearly 4000 flares of 61 giants and 20 stars of other types that were observed with Kepler in long-cadence mode, which is the only suitable database for this comparative study. For every flare, we derived the duration and energy and gathered stellar parameters. Correlations between the flare characteristics and various stellar parameters were investigated.
Results. Strong correlations are found between the flare duration and the surface gravity, luminosity, and radii of the stars. Scaled flare shapes appear to be similar on giants and dwarfs with a 30 min cadence. The logarithmic relation of flare energy and duration is steeper for stars with lower surface gravity. Observed flares are longer and more energetic on giants than on dwarfs on average.
Conclusions. The generalized linear scaling for the logarithmic relation of flare energy and duration with a universal theoretical slope of ≈1/3 should slightly be modified by introducing a dependence on surface gravity.
Key words: stars: activity / stars: late-type / stars: flare
Full Tables 1 and 2 are only available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/668/A101
© K. Oláh et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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