J/A+A/637/A22 M dwarfs rotation-activity relations and flares (Raetz+, 2020)
Rotation-activity relations and flares of M dwarfs with K2 long- and
short-cadence data.
Raetz S., Stelzer B., Damasso M., Scholz A.
<Astron. Astrophys. 637, A22 (2020)>
=2020A&A...637A..22R 2020A&A...637A..22R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type; Stars, flare
Keywords: stars: late-type - stars: activity - stars: rotation - stars: flare
Abstract:
Using light curves obtained by the K2 mission, we study the relation
between stellar rotation and magnetic activity with a special focus on
stellar flares. Our sample comprises 56 bright and nearby M dwarfs
observed by K2 during campaigns C0-C18 in long and short cadence mode.
We derive rotation periods for 46 M dwarfs and measure photometric
activity indicators such as amplitude of the rotational signal,
standard deviation of the light curves, and the basic flare properties
(flare rate, flare energy, flare duration, flare amplitude). We found
1662 short cadence flares of which 363 have a long cadence counterpart
with flare energies up to 5.6*1034erg. The flare amplitude, duration
and flare frequency derived from the short cadence LCs differ
significantly from the ones derived from the long cadence data. The
analysis of the short cadence light curves results in a 4.6 times
higher flare rate than the long cadence data. We confirm the abrupt
change of the activity level in the rotation-activity relation at a
critical period of ∼10d when photometric activity diagnostics are
used. This change is most drastic in the flare duration and the flare
frequency for short cadence data. Our flare studies revealed that the
highest flare rates are not found among the fastest rotators and that
the stars with the highest flare rates do not show the most energetic
flares. We found a ∼2 times larger superflares frequency
(>5*1034erg) for the fast rotating M stars than for solar like stars
in the same period range. By fitting the cumulative flare frequency
distribution we derived a power-law index of alpha=1.84±0.14
consistent with previous M dwarf studies and the value found for the
Sun.
Description:
Stellar parameters, rotation period and activity indicators obtained
in short and long cadence LCs for all 56 stars in our K2 M dwarf
sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 86 56 Stellar parameters for all stars in our sample
tableb2.dat 72 56 Rotation period and activity indicators obtained
in short and long cadence LCs for all 56 stars
in our K2 M dwarf sample
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See also:
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- EPIC EPIC identification number
11- 17 A7 --- Campaign K2 observing campaign
19- 23 F5.2 mag Kpmag Apparent magnitude in the Kepler band
25- 29 F5.2 [10-7W] logL(Kp0) Quiescent luminosity in the Kepler band,
logL(Kp,0)
31- 34 F4.2 mag KsMAG Absolute magnitude in the 2MASS K-band
36- 39 F4.2 mag e_KsMAG Uncertainty on MKs
41- 44 F4.2 Rsun Rs Stellar radius
46- 49 F4.2 Rsun e_Rs Uncertainty on stellar radius
51- 55 F5.3 Msun Ms Stellar mass
57- 61 F5.3 Msun e_Ms Uncertainty on stellar mass
63- 66 I4 K Teff Effective temperature
68- 69 I2 K e_Teff Uncertainty on effective temperature
71- 75 F5.2 pc d Distance
77- 80 F4.2 pc e_d Uncertainty on distance
82- 86 F5.2 --- SpType Spectral type given as subclass of M dwarfs
(negative values correspond to spectral types
earlier than M)
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Byte-by-byte Description of file: tableb2.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- EPIC EPIC identification number
11- 17 A7 --- Campaign K2 observing campaign
19- 23 F5.2 d Prot ? Stellar rotation period
25- 28 F4.2 % Rper ? Full amplitude of the rotation signal
30- 34 F5.2 [10-7J] logE(Fmax) ? Maximum flare energy, logE(F,max)
36- 40 I5 ppm Sph Standard deviation of the full light curve
42- 46 I5 ppm Sflat(SC) Standard deviation of the flattened and
cleaned short cadence light curve
48- 50 I3 --- Nflares(SC) Number of short cadence flares
52- 57 F6.4 d-1 nu(SC) ? Flare frequency in short cadence,
in Nfares/d unit
59- 62 I4 ppm Sflat(LC) Standard deviation of the flattened and
cleaned long cadence light curve
64- 65 I2 --- Nflares(LC) Number of long cadence flares
67- 72 F6.4 d-1 nu(LC) ? Flare frequency in long cadence,
in Nfares/d unit
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Acknowledgements:
Stefanie Raetz, raetz(at)astro.uni-tuebingen.de
(End) Stefanie Raetz [IAAT, Germany], Patricia Vannier [CDS] 19-Mar-2020