J/ApJ/906/40 Activity & Magnetic Analysis of Flare Stars. II. (Goodarzi+, 2021)
Flare Activity and Magnetic Feature Analysis of the Flare Stars.
II. Subgiant Branch.
Goodarzi H., Mehrabi A., Khosroshahi H. G, He H.
<Astrophys. J., 906, 40 (2021)>
=2021ApJ...906...40G 2021ApJ...906...40G
ADC_Keywords: Stars, F-type; Stars, G-type; Stars, diameters; Stars, masses;
Abundances, [Fe/H]; Effective temperatures ; Optical
Keywords: Magnetic stars ; Flare stars ; Stellar activity ; F subgiant
stars ; G subgiant stars ; K subgiant stars ; Main sequence ;
Starspots
Abstract:
We present an investigation of the magnetic activity and flare
characteristics of the subgiant stars mostly from F and G spectral
types and compare the results with the main-sequence (MS) stars. The
light curve of 352 stars on the subgiant branch (SGB) from the Kepler
mission is analyzed in order to infer stability, relative coverage,
and contrast of the magnetic structures and also flare properties
using three flare indexes. The results show the following. (I)
Relative coverage and contrast of the magnetic features along with
rate, power, and magnitude of flares increase on the SGB due to the
deepening of the convective zone and more vigorous magnetic field
production. (II) Magnetic activity of the F- and G-type stars on the
SGB does not show dependency on the rotation rate and does not obey
the saturation regime. This is the opposite of what we saw for the MS,
in which the G-, K-, and M-type stars show clear dependency on the
Rossby number. (III) The positive relationship between the magnetic
features' stability and their relative coverage and contrast remains
true on the SGB; though, it has a lower dependency coefficient in
comparison with the MS. (IV) Magnetic proxies and flare indexes of the
SGB stars increase with increasing relative mass of the convective
zone.
Description:
We select subgiant stars from the revised radii and evolutionary state
catalog (Berger+, 2018, J/ApJ/866/99). We choose the targets whose
flare activity was confirmed in either of the catalogs Davenport+,
2016, J/ApJ/829/23 or Van Doorsselaere+, 2017,J/ApJS/232/26 , and
their rotation period was determined in the catalog by McQuillan+,
2014, J/ApJS/211/24. We also remove all the binary candidates reported
by Berger+. Final sample contains 352 single-, flare-, subgiant stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 129 352 Parameters of Kepler subgiant flare stars
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/A+A/531/A8 : Activity indices and velocities for 890 stars (Jenkins+, 2011)
J/AJ/141/50 : White-light flares on cool stars from Kepler (Walkowicz+, 2011)
J/ApJ/743/48 : Stars with rotation periods & X-ray luminosity (Wright+, 2011)
J/ApJS/209/5 : Superflares of Kepler stars. I. (Shibayama+, 2013)
J/ApJ/776/67 : Rotational tracks (van Saders+, 2013)
J/ApJ/788/L9 : Stellar parameters of KIC planet-host stars (Bastien+, 2014)
J/A+A/572/A34 : Pulsating solar-like stars in Kepler (Garcia+, 2014)
J/ApJS/211/2 : Revised stellar properties Q1-16 Kepler targets (Huber+, 2014)
J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)
J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)
J/ApJ/834/207 : Periodicity & magnitude Kepler LCs variation (Mehrabi+, 2017)
J/ApJS/232/26 : Catalog of Kepler flare stars (Van Doorsselaere+, 2017)
J/ApJ/866/99 : Radii of KIC stars & planets using Gaia DR2 (Berger+, 2018)
J/ApJS/244/37 : Kepler flare star parameters from DR25 (Goodarzi+, 2019)
J/ApJS/241/2 : Ionization profiles of 8 Galactic H II regions (Luisi+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- KIC Kepler catalog identifier
10- 15 F6.3 d Per [0.21/36.4] Stellar rotation period
17- 25 F9.7 --- IAC [0.11/0.43] Auto-correlation index
27- 35 F9.7 --- Reff [0.0001/0.1] Effective range light curve variation
37- 45 F9.7 --- Rf [0.0007/0.03] Time occupation ratio of flares
47- 59 E13.7 --- Pf [2.58e+20/2.04e+23] Total power of flares
61- 73 E13.7 --- Mf [1.09e+23/2.7e+25] Average flux magnitude flares
75- 83 F9.7 --- Thr [0.0001/0.009] Threshold value of flare detection
85- 87 I3 --- Nf [38/672] Number of flares
89- 94 F6.4 Msun Mass [0.8/1.27] Stellar mass
96-100 F5.3 Rsun Rad [0.6/3.77] Stellar radius
102-107 F6.1 K Teff [5004/6709] Stellar effective temperature
109-113 F5.3 [cm/s2] logg [3.58/4.68] log stellar surface gravity
115-119 F5.2 [-] Fe/H [-1.54/0.56] Metallicity
121-129 F9.7 --- Ro [0.02/2.01] Rossby number
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History:
From electronic version of the journal
References:
Goodarzi et al. Paper I : 2019ApJS..244...37G 2019ApJS..244...37G
(End) Prepared by [AAS], Coralie Fix [CDS], 16-May-2022