J/MNRAS/502/2033 Flares in the Kepler short cadence data (Jackman+, 2021)
Stellar flares from blended and neighbouring stars in Kepler short cadence
observations.
Jackman J.A.G., Shkolnik E., Loyd R.O.P.
<Mon. Not. R. Astron. Soc., 502, 2033-2042 (2021)>
=2021MNRAS.502.2033J 2021MNRAS.502.2033J (SIMBAD/NED BibCode)
ADC_Keywords: Stars, flare ; Effective temperatures ; Stars, diameters ;
Optical
Keywords: stars: flare - stars: low-mass
Abstract:
We present the results of a search for stellar flares from stars
neighbouring the target sources in the Kepler short cadence data.
These flares have been discarded as contaminants in previous surveys
and therefore provide an unexplored resource of flare events, in
particular high-energy events from faint stars. We have measured M
dwarf flare energies up to 1.5x1035erg, pushing the limit for flare
energies measured using Kepler data. We have used our sample to study
the flaring activity of wide binaries, finding that the lower mass
counterpart in a wide binary flares more often at a given energy. Of
the 4430 flares detected in our original search, 298 came from a
neighbouring star, a rate of 6.7±0.4 per cent for the Kepler short
cadence light curves. We have used our sample to estimate a 5.8±0.1
per cent rate of false positive flare events in studies using
Transiting Exoplanet Survey Satellite short cadence data.
Description:
In this work we have presented the results of a search for stellar
flares in the Kepler short cadence data. We specifically searched for
flares which came from stars neighbouring the target sources, which
have been excluded from previous surveys. From our search of the short
cadence light curves using the original Kepler apertures we initially
detected 4430 flares from 403 stars. We identified that 515 flares in
26 Kepler short cadence light curves were either due to a nearby
source, or due to there being flares from both the target star and a
close companion. From the 26 Kepler light curves there were 34
individual flaring stars, 26 of which were neighbouring the target
source. The remaining eight were cases when both stars in the postage
stamp flared. Further inspection with revised apertures, resulted in
an extra 68 flare detections from nearby stars, increasing the total
number of flares to 4498, with 583 flares from 34 stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 92 14 Best-fitting power-law parameters for the flare
occurrence rates of stars in our sample
table2.dat 96 4 Flare occurrence rate ratios for stars in wide
binaries where at least one component had a
measured flare occurrence rate
flares.dat 218 583 Supplementary stellar and flare information
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- --- [Gaia DR2]
10- 28 I19 --- GaiaDR2 Gaia DR2 source identifier
30 I1 --- f_GaiaDR2 [1/2]? Flag on Name (1)
32- 35 I4 K Teff Effective temperature
37- 39 I3 K E_Teff Upper error on Teff
41- 43 I3 K e_Teff Lower error on Teff
45- 48 F4.1 --- C Best fitting value of the normalization
constant C (2)
50- 53 F4.1 --- e_C Error on C
55- 58 F4.2 --- alpha Best fitting value of the power-law index
α (3)
60- 63 F4.2 --- e_alpha Error on alpha
65- 71 E7.2 10-7J Elim Minimum energy limit used when fitting the
power-law distribution
73- 79 E7.2 10-7J Emax Maximum flare energy
81 A1 --- f_Emax [*] Flag on Emax (4)
83- 84 I2 --- Nflares Number of flares used in the fitting
86- 92 F7.1 d Timewait Predicted waiting time to observe a flare
with an energy of 1033erg or greater
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Note (1): Flag as follows:
1 = Gaia DR2 2131725447350716032 and Gaia DR2 2131725451649506944 are both
components of the same wide binary
2 = Gaia DR2 2079073928612819840 and Gaia DR2 2079073928612821760 are both
components of the same wide binary
Note (2): The number of flares which occur with an energy greater than E can
then be written as logN(Efl>E)=C+βlogE, where C is a
normalization constant and β=1-α
Note (3): Previous studies have shown that flares occur with a power-law-like
distribution in energy, written as dN(E)∝E-αdE, where
N(E) is the number of flares in a given duration with energy E and
α is the power-law index
Note (4): Flag as follows:
* = This star had an upper energy limit of 2x1031erg imposed when fitting
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 28 A28 --- GaiaDR21 Gaia DR2 source identifier of the wide binary
first component
30- 33 I4 K Teff1 Effective temperature of the wide binary
first component
35- 37 I3 K E_Teff1 Upper error on Teff1
39- 41 I3 K e_Teff1 Lower error on Teff1
43- 70 A28 --- GaiaDR22 Gaia DR2 source identifier of the wide binary
second component
72- 75 I4 K Teff2 Effective temperature of the wide binary
second component
77- 79 I3 K E_Teff2 Upper error on Teff2
81- 83 I3 K e_Teff2 Lower error on Teff2
85- 91 E7.2 10-7J Eflare Flare energy (1)
93- 96 F4.1 --- Ratio Flare occurrence rate ratio of 1 to 2
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Note (1): The flare energy is the maximum measured energy for the less active
component. For non-equal mass binaries, this is the hotter component
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Byte-by-byte Description of file: flares.dat
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Bytes Format Units Label Explanations
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1- 28 A28 --- Name Star name
30- 44 F15.11 deg RAdeg Right ascension (ICRS) at Ep=2015.5
46- 59 F14.11 deg DEdeg Declination (ICRS) at Ep=2015.5
61- 67 F7.2 K Teff ? Effective temperature
69- 75 F7.2 K e_Teff ? Lower error on Teff
77- 83 F7.2 K E_Teff ? Upper error on Teff
85- 92 F8.6 Rsun Rad ? Star radius
94-101 F8.6 Rsun e_Rad ? Lower error on Rad
103-110 F8.6 Rsun E_Rad ? Upper error on Rad
112-119 F8.3 d Start Flare start time
121-128 F8.3 d End Flare end time
130-139 F10.8 mag Ampdet Detected flare amplitude
141-151 F11.8 mag Ampadj ? Adjusted flare amplitude
153-163 E11.6 10-7J Eflare ? Flare energy
165-175 E11.6 10-7J e_Eflare ? Lower error on Eflare
177-187 E11.6 10-7J E_Eflare ? Upper error on Eflare
189-196 F8.3 d Duration Observed duration
198-207 F10.8 --- DilKep ? Kepler dilution (1)
209-218 F10.8 --- DilTESS ? TESS dilution (1)
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Note (1): The dilution is calculated as the ratio of the flux from the flaring
stars to the flux from all stars within the aperture
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 30-Oct-2023