Volume 622, February 2019
|Number of page(s)||16|
|Section||Stellar structure and evolution|
|Published online||07 February 2019|
Flares in open clusters with K2⋆
I. M 45 (Pleiades), M 44 (Praesepe), and M 67
Leibniz-Institut für Astrophysik Potsdam, Germany
2 University of Washington, USA
Accepted: 14 December 2018
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.
Key words: methods: data analysis / stars: activity / stars: flare / stars: low-mass
The detected flare indices, the stellar parameters for M 44 and M 45, and a copy of Table 4 are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/622/A133. We also published all flares we validated, and stellar parameters used for M 44 and M 45 in the same location.
© ESO 2019
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.