J/A+A/556/A52 γ Dor stars from Kepler (Tkachenko+, 2013)
Detection of a large sample of gamma Dor stars from Kepler space photometry and
high-resolution ground-based spectroscopy.
Tkachenko A., Aerts C., Yakushechkin A., Debosscher J., Degroote P.,
Bloemen S., Papics P.I., de Vries B.L., Lombaert R., Hrudkova M.,
Fremat Y., Raskin G., Van Winckel H.
<Astron. Astrophys. 556, A52 (2013)>
=2013A&A...556A..52T 2013A&A...556A..52T
ADC_Keywords: Stars, variable ; Stars, F-type
Keywords: asteroseismology - stars: variables: general -
stars: fundamental parameters - stars: oscillations
Abstract:
The launches of the MOST, CoRoT, and Kepler missions opened up a new
era in asteroseismology, the study of stellar interiors via
interpretation of pulsation patterns observed at the surfaces of large
groups of stars. These space missions deliver a huge amount of
high-quality photometric data suitable to study numerous pulsating
stars.
Our ultimate goal is a detection and analysis of an extended sample of
γ Dor-type pulsating stars with the aim to search for
observational evidence of non-uniform period spacings and rotational
splittings of gravity modes in main-sequence stars typically twice as
massive as the Sun. This kind of diagnostic can be used to deduce the
internal rotation law and to estimate the amount of rotational mixing
in the near core regions.
We applied an automated supervised photometric classification method
to select a sample of 69 Gamma Doradus (γ Dor) candidate stars.
We used an advanced method to extract the Kepler light curves from the
pixel data information using custom masks. For 36 of the stars, we
obtained high-resolution spectroscopy with the HERMES spectrograph
installed at the Mercator telescope. The spectroscopic data are
analysed to determine the fundamental parameters like Teff, log g,
vsini, and [M/H].
We find that all stars for which spectroscopic estimates of Teff and
log g are available fall into the region of the HR diagram, where
the γ Dor and δ Sct instability strips overlap. The stars
cluster in a 700 K window in effective temperature; log g
measurements suggest luminosity class IV-V, i.e. sub-giant or
main-sequence stars. From the Kepler photometry, we identify 45
γ Dor-type pulsators, 14 γ Dor/δ Sct hybrids, and 10
stars, which are classified as "possibly γ Dor/δ Sct
hybrid pulsators". We find a clear correlation between the
spectroscopically derived vsini and the frequencies of independent
pulsation modes.
Description:
We base our analysis on high-quality photometric and spectroscopic
data. The light curves have been gathered by the Kepler space
telescope and are of micro-magnitude precision. For the analysis, we
use all publicly available data at the time of the analysis (Q0-Q8)
and our data from the Kepler Guest Observer data (GO, Still et al.
2011, BAAS, 43, #140.02). Instead of using the standard pre-extracted
light curves delivered through MAST (Mikulski Archive for Space
Telescopes), we have extracted the light curves from the pixel data
information using custom masks based on software developed by one of
us (SB, Bloemen et al., in prep).
We acquired high-resolution spectroscopy for the brightest targets
with the HERMES (High Efficiency and Resolution Mercator Echelle
Spectrograph) spectrograph attached to the 1.2-m Mercator telescope
(La Palma, Canary Islands). The spectra have a resolution of 85000 and
cover the wavelength range from 377 to 900nm. Typical S/Ns measured at
λλ5500Å are about 40 for each spectrum.
Files contain information on the detected in the Kepler curve
frequencies, their amplitudes and significance level, as well as
identification (independent or a combination).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
target.dat 126 69 Photometric classification and characterization
of the sample targets (table3 of the paper)
freq/* . 69 Individual list of statistically significant
frequencies
table70.dat 33 205 List of Delta Scuti stars extracted from
Rodriguez et al. (2000, Cat. J/A+AS/144/469) and
Uytterhoeven et al. (2011, Cat. J/A+A/534/A125)
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/A+AS/144/469 : Delta Scuti stars (Rodriguez+, 2000)
J/A+A/472/241 : UV Flux distributions of gamma Dor stars (Gerbaldi+, 2007)
J/AJ/133/1421 : BV diff. photometry of 11 gamma Dor stars (Henry+, 2007)
J/A+A/499/967 : Long-term monitoring of γ Dor stars (Cuypers+, 2009)
J/A+A/534/A125 : Variability of A- and F-stars from Kepler (Uytterhoeven+ 2011)
J/A+A/552/A60 : CoRoT 102918586 light curve and spectra (Maceroni+, 2013)
J/A+A/556/A56 : KIC 11285625: list of detected frequencies (Debosscher+, 2013)
Byte-by-byte Description of file: target.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [KIC]
4- 11 I8 --- KIC KIC number
13- 18 F6.4 d-1 Res Frequency resolution
20- 30 A11 --- FileName Name of the file with list of frequencies in
subdirectory freq
32- 35 F4.2 d-1 b_Freqd Lower value of frequency interval in d-1
37- 41 F5.2 d-1 B_Freqd Upper value of frequency interval in d-1
45- 48 F4.2 uHz b_FreqH Lower value of frequency interval in µHz
50- 55 F6.2 uHz B_FreqH Upper value of frequency interval in µHz
59- 62 F4.2 mmag b_Amp Lower value of amplitude range
64- 68 F5.2 mmag B_Amp Upper value of amplitude range
71- 77 F7.4 d-1 FreqHiD Frequency of the highest amplitude peak
in d-1
79- 86 F8.4 uHz FreqHiH Frequency of the highest amplitude peak
in µHz
88- 90 I3 --- N Total number of statistically significant
frequencies
92-121 A30 --- Class Photometric classification
126 A1 --- n_Class [*] * for Possibly γ Dor/δ Sct
hybrid
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Byte-by-byte Description of file: freq/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- F Frequency running number
5- 11 F7.4 d-1 Freq1 Frequency (in d-1) from Fourier analysis (1)
13- 20 F8.4 uHz Freq2 Frequency (in µHz) from Fourier analysis
22- 28 F7.4 mmag Amp Amplitude in mmag
30- 34 F5.4 mmag e_Amp rms uncertainty on Amp
40- 44 F5.1 --- SNR Frequency significance in terms of S/N
46- 63 A18 --- Comb Lowest order combination (2)
65- 66 I2 --- N [-1/11] Number of combinations that can be
built of the independent frequencies only (3)
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Note (1): Frequency uncertainty is given by Reyleigh limit
Note (2): "independent" stands for the independent frequency
Note (3): "-1" stands for the independent frequency. "0" means that that the
frequency of interest can only be represented as a combination of the
frequencies which themselves are combinations of the independent peaks.
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Byte-by-byte Description of file: table70.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Star designation
12- 18 F7.4 d-1 Freq1 Frequency in d-1
20- 27 F8.4 uHz Freq2 Frequency in µHz
29- 31 I3 km/s vsini Projected rotation velocity
33 I1 --- Ref [1/2] Literature source (1)
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Note (1): Source as follows:
1 = Rodriguez et al. (2000, Cat. J/A+AS/144/469)
2 = Uytterhoeven et al. (2011, Cat. J/A+A/534/A125)
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Acknowledgements:
Andrew Tkachenko,
History:
* 24-Jul-2013: On-line version
* 18-Feb-2015: target file (list + table3) added
(End) Andrew Tkachenko [IvS, Leuven], Patricia Vannier [CDS] 07-Jun-2013