J/MNRAS/492/3143 Rotation and spots in normal A and Am/Fm stars (Trust+, 2020)
Rotation and spots in normal A and Am/Fm stars.
Trust O., Jurua E., De Cat P., Joshi S.
<Mon. Not. R. Astron. Soc., 492, 3143-3155 (2020)>
=2020MNRAS.492.3143T 2020MNRAS.492.3143T (SIMBAD/NED BibCode)
ADC_Keywords: Stars, A-type ; Stars, Am ; Rotational velocities ;
Effective temperatures ; Stars, diameters ; Optical
Keywords: stars: chemically peculiar - stars: general - stars: rotation
Abstract:
Frequency analysis of long-term ultraprecise photometry can lead to
precise values of rotation frequencies of rotating stars with 'hump
and spike' features in their periodograms. Using these features, we
computed the rotation frequencies and amplitudes. The corresponding
equatorial rotational velocity (Vrot) and spot size were estimated.
On fitting the autocorrelation functions of the light curves with the
appropriate model, we determined the star-spot decay time-scale. The
Vrot agrees well with the projected rotational velocity (vsini) in
the literature. Considering a single circular and black spot, we
estimate its radius from the amplitude of the 'spike'. No evidence for
a significant difference in the average 'spike' amplitude and spot
radius was found for Am/Fm and normal A stars. Indeed, we derived an
average value of ∼21±2 and ∼19±2ppm for the photometric amplitude
and of 1.01±0.13 and 1.16±0.12RE for the spot radius (where RE
is the Earth radius), respectively. We do find a significant
difference for the average spot decay time-scale, which amounts to
3.6±0.2 and 1.5±0.2d for Am/Fm and normal A stars, respectively.
In general, spots on normal A stars are similar in size to those on
Am/Fm stars, and both are weaker than previously estimated. The
existence of the 'spikes' in the frequency spectra may not be strongly
dependent on the appearance of star-spots on the stellar surface. In
comparison with G, K, and M stars, spots in normal A and Am/Fm stars
are weak, which may indicate the presence of a weak magnetic field.
Description:
Of the 875 rotationally modulated main-sequence normal A stars studied
by Balona (2013MNRAS.431.2240B 2013MNRAS.431.2240B, Cat. J/MNRAS/431/2240) and the 15
Am/Fm stars from the nominal Kepler mission analysed by Balona et al.
(2015MNRAS.448.1378B 2015MNRAS.448.1378B), only the normal A and Am/Fm stars with 'hump
and spike' features in their frequency spectra were considered.
Additional Am/Fm stars with 'hump and spike' features in the frequency
spectra were derived from the sources analysed by Gray et al.
(2016AJ....151...13G 2016AJ....151...13G, Cat. J/AJ/151/13) under the LAMOST-Kepler
project (De Cat et al. 2015ApJS..220...19D 2015ApJS..220...19D, Cat. J/ApJS/220/19). A
total of 170 'hump and spike' stars were obtained of which 131 are
normal A stars reported by Balona (2013MNRAS.431.2240B 2013MNRAS.431.2240B, Cat.
J/MNRAS/431/2240), and 39 are normal Am/Fm stars from Balona et al.
(2015MNRAS.448.1378B 2015MNRAS.448.1378B) (3 stars) and from Gray et al.
(2016AJ....151...13G 2016AJ....151...13G, Cat. J/AJ/151/13) (36 stars).
For this study, we used the high-precision and almost continuous
photometric data obtained by the Kepler mission. The data are
available on the Barbara A. Mikulski Archive for Space Telescopes
(MAST) website (http://archive.stsci.edu/).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 140 131 List of normal A stars with 'hump and spike'
features in the frequency spectra
tablea2.dat 140 39 List of Am/Fm stars with 'hump and spike'
features in the frequency spectra
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/MNRAS/431/2240 : Activity in A-type stars from Kepler (Balona, 2013)
J/AJ/151/13 : LAMOST-Kepler MKCLASS spectral classification (Gray+, 2016)
J/ApJS/220/19 : LAMOST obs. in the Kepler field. I. (De Cat+, 2015)
J/ApJS/229/30 : Revised stellar properties of Q1-17 Kepler targets
(Mathur+, 2017)
Byte-by-byte Description of file: tablea1.dat tablea2.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- KIC KIC object identifier
10- 16 F7.5 d-1 frot Rotation frequency
18- 22 F5.3 mmag Arot Photometric amplitude
24- 28 F5.3 mmag e_Arot Error on Arot
30- 36 F7.5 d-1 fhar ? Frequency equivalent to 2*frot
38- 42 F5.3 mmag Ahar ? Amplitude associated to fhar
44- 48 F5.3 mmag e_Ahar ? Error on Ahar
50- 54 I5 K Teff Effective temperature (1)
56- 58 I3 K e_Teff Error on Teff
60- 64 F5.3 [cm/s2] logg Surface gravity
66- 70 F5.3 [cm/s2] e_logg Error on logg
72- 77 F6.3 [Lsun] logL Logarithm of the luminosity (2)
79- 83 F5.3 [Lsun] e_logL Error on logL
85- 88 F4.2 Rsun R Radius (3)
90- 93 F4.2 Rsun e_R Error on R
95- 97 I3 km/s Vrot Equatorial rotational velocity
99-100 I2 km/s e_Vrot Error on Vrot
102-104 I3 km/s vsini ? Projected rotational velocity
106-109 F4.2 Rgeo Rspot Radius of the spot (4)
111-114 F4.2 Rgeo e_Rspot Error on Rspot
116-120 F5.3 d PACF ? Stellar rotation period
122-127 F6.3 d e_PACF ? Error on PACF
129-134 F6.3 d tau Decay time-scale of the dominant active
region
136-140 F5.3 d e_tau ? Error on tau
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Note (1): We adopted the effective temperature from the revised catalogue of
Kepler targets for the Q1-17 by Mathur et al. (2017ApJS..229...30M 2017ApJS..229...30M,
Cat. J/ApJS/229/30)
Note (2): We derived the luminosity parameter from Gaia parallaxes
(Gaia Collaboration et al. 2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345)
Note (3): We used the mean stellar radius that we calculated from
log(R/R☉)=0.5log(L/L☉)-2.0log(Teff_)+7.52340473
Note (4): The radius of the spot is given by the standard relation
Rspot=Arotsqrt(R)
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 21-Mar-2023