J/A+A/622/A133 M45, M44 and M67 flare stars (Ilin+, 2019)
Flares in Open Clusters with K2.
I. M 45 (Pleiades), M 44 (Praesepe) and M 67.
Ilin E., Schmidt S.J., Davenport J.R.A., Strassmeier K.G.
<Astron. Astrophys. 622, A133 (2019)>
=2019A&A...622A.133I 2019A&A...622A.133I (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, flare ; Photometry, SDSS ;
Photometry, infrared
Keywords: methods: data analysis - stars: activity - stars: flare -
stars: low-mass
Abstract:
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"? 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. 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,
M45 (0.125Gyr), M44 (0.63Gyr), and M67 (4.3Gyr). We updated and
employed the automated flare finding and analysis pipeline Appaloosa,
originally designed for Kepler. We introduced a synthetic flare
injection and recovery subroutine to ascribe detection and energy
recovery rates for flares in a broad energy range for each light
curve. We collected a sample of 1761 stars, mostly late-K to mid-M
dwarfs and found 751 flare candidates with energies ranging from
4x1032erg to 6x1034erg, of which 596 belong to M45, 155 to M44,
and none to M67. We find that flaring activity depends both on Teff,
and age. But all flare frequency distributions have similar slopes
with alpha from 2.0 to 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.
Description:
Using K2SC de-trended Kepler/K2 LCs we investigated the flaring
activity of three solar metallicity OCs, the ZAMS cluster M 45,
intermediate age M 44 and solar age M 67, a total of more than 250
years of cumulative observation time at 30-min cadence from 1761
targets, mostly late-K and early- to mid-M dwarfs. Pan-STARRS and
2MASS multiband photometry yielded Teff and radii of individual stars,
using solar metallicity standards (Pickles, 1998PASP..110..863P 1998PASP..110..863P),
computed by Covey et al. (2007, Cat. J/AJ/134/2398), and
colour-temperature relations from Pecaut & Mamajek (2013, Cat.
J/ApJS/208/9). From these we derived quiescent luminosities and the
Kepler band energies of flares detected by the flare finding and
analysis pipeline Appaloosa (Davenport 2016, Cat. J/ApJ/829/23).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
allflare.dat 72 751 Indices into light curves to find flares
alphabet.dat 166 10 Stellar parameters for M44 and M45 members
cparam.dat 323 1620 Power law fits to bin-wise flare frequency
distributions
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See also:
J/ApJS/208/9 : Intrinsic colors & temperatures of PMS stars (Pecaut+, 2013)
J/ApJ/795/161 : Activity and rotation in Praesepe and Hyades (Douglas+ 2015)
J/AJ/152/113 : Pleiades members with K2 light curves. I. Periods
(Rebull+ 2016)
J/MNRAS/459/1060 : M67 variable stars from Kepler/K2-Campaign-5 (Gonzalez 2016)
Byte-by-byte Description of file: allflare.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- EPIC K2 ID
11- 14 I4 K Teff Effective temperature
16- 18 A3 --- Cluster Cluster designation
20- 40 E21.14 erg Ekpflare Kepler flare energy
42- 62 E21.14 erg e_Ekpflare Kepler flare energy uncertainty
64- 67 I4 --- start Flare start index into K2SC light curve
69- 72 I4 --- stop Flare stop index into K2SC light curve
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Byte-by-byte Description of file: alphabet.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Cluster Cluster designation
5- 8 I4 K Tmin Minimum Teff in bin
10- 13 I4 K Tmax Maximum Teff in bin
15- 17 I3 --- nLC Number of light curves in bin
19- 21 I3 --- nflares Number of flares in bin
23- 38 F16.14 --- alpha Power law exponent Eq. (12) of the paper
40- 56 F17.15 --- e_alpha Power law exponent uncertainty
58- 73 F16.13 [-] log10beta Power law factor Eq. (12) of the paper
75- 91 F17.15 [-] e_log10beta Power law factor uncertainty Eq. (12)
of the paper
93-108 F16.13 [-] log10beta2 Power law factor Eq. (12) of the paper
with alpha fixed at 2
110-126 F17.15 [-] E_log10beta2 Power law factor upper uncertainty Eq. (12)
of the paper with alpha fixed at 2
128-144 F17.15 [-] e_log10beta2 Power law factor upper uncertainty Eq. (12)
of the paper with alpha fixed at 2
146-166 E21.14 10-7J detthresh Minimum Kepler flare energy in bin
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Byte-by-byte Description of file: cparam.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- EPIC K2 ID
12- 21 F10.6 deg RAdeg Right ascension (J2000)
24- 33 F10.6 deg DEdeg Declination (J2000)
35 I1 --- Campaign K2 Campaign
37- 40 A4 --- SpClass Dwarf spectral class
42- 46 I5 K Teff Effective temperature
48- 52 F5.3 [K] logTeff log10 effective temperature as in Pecaut and
Mamajek (2013, Cat. J/ApJS/208/9)
54- 58 F5.2 [10-7W] logL log10 luminosity as in Pecaut and Mamajek
(2013, Cat. J/ApJS/208/9)
60- 64 F5.2 mag Jmag 2MASS J band magnitude
66- 69 F4.2 mag Ksmag 2MASS Ks band magnitude
71- 75 F5.2 mag mbol Bolometric magnitude as in Pecaut and
Mamajek (2013, Cat. J/ApJS/208/9)
77- 81 F5.3 Rsun Rad Stellar radius as in Pecaut and Mamajek
(2013, Cat. J/ApJS/208/9)
83- 89 F7.2 mag u-g ?=-999 SDSS u-g color index
91- 97 F7.2 mag g-r ?=-999 SDSS g-r color index
99-105 F7.2 mag r-i ?=-999 SDSS r-i color index
107-113 F7.2 mag i-z ?=-999 SDSS i-z color index
115-121 F7.2 mag z-J ?=-999 SDSS-2MASS z-J color index
123-129 F7.2 mag J-H ?=-999 2MASS J-H color index
131-137 F7.2 mag H-K ?=-999 2MASS H-K color index
139-145 F7.2 mag JMAG ?=-999 Absolute J magnitude as in Pecaut and
Mamajek (2013, Cat. J/ApJS/208/9)
147-164 F18.13 K e_Teff Uncertainty of effective temperature
166-171 F6.4 Rsun e_Rad Uncertainty on stellar radius
173-189 F17.15 mag e_mbol Uncertainty on bolometric magnitude
191-211 E21.14 10-7W Lquiet ?=-999 Quiescent Kepler luminosity
213-233 E21.14 10-7W Lquietbol Quiescent bolometric luminosity
235-255 E21.14 10-7W e_Lquiet ?=-999 Quiescent Kepler luminosity
uncertainty
257-277 E21.14 10-7W e_Lquietbol Quiescent bolometric luminosity uncertainty
279 I1 --- todrop [0/1] Light curve was dropped, yes is 1
281-295 A15 --- whydrop Reason why light curve was dropped
297-300 I4 --- nappaflares ?=-999 Number of flare in light curve
302-319 F18.13 d t ?=-999 Total observing time
321-323 A3 --- Cluster Cluster designation
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Acknowledgements:
Ekaterina Ilin, eilin(at)aip.de
(End) Patricia Vannier [CDS] 30-Dec-2018