Flares in open clusters with K2 . I. M 45 (Pleiades), M 44 (Praesepe), and M 67
Abstract
Context. The presence and strength of a stellar magnetic field and activity is rooted in a star's fundamental parameters such as mass and age. Can flares serve as an accurate stellar "clock"?
Aims: To explore if we can quantify an activity-age relation in the form of a flaring-age relation, we measured trends in the flaring rates and energies for stars with different masses and ages.
Methods: We investigated the time-domain photometry provided by Kepler's follow-up mission K2 and searched for flares in three solar metallicity open clusters with well-known ages, M 45 (0.125 Gyr), M 44 (0.63 Gyr), and M 67 (4.3 Gyr). We updated and employed the automated flare finding and analysis pipeline Appaloosa, originally designed for Kepler. We introduced a synthetic flare injection and recovery sub-routine to ascribe detection and energy recovery rates for flares in a broad energy range for each light curve.
Results: We collect a sample of 1761 stars, mostly late-K to mid-M dwarfs and found 751 flare candidates with energies ranging from 4 × 1032 erg to 6 × 1034 erg, of which 596 belong to M 45, 155 to M 44, and none to M 67. We find that flaring activity depends both on Teff, and age. But all flare frequency distributions have similar slopes with α ≈ 2.0-2.4, supporting a universal flare generation process. We discuss implications for the physical conditions under which flares occur, and how the sample's metallicity and multiplicity affect our results.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- February 2019
- DOI:
- 10.1051/0004-6361/201834400
- arXiv:
- arXiv:1812.06725
- Bibcode:
- 2019A&A...622A.133I
- Keywords:
-
- methods: data analysis;
- stars: activity;
- stars: flare;
- stars: low-mass;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 17 pages, 11 figures, appendix. Accepted to A&