J/A+A/525/A131Solar-like oscillations in Kepler red giants (Hekker+, 2011)

Solar-like oscillations in red giants observed with Kepler: comparison of global oscillation parameters from different methods. Hekker S., Elsworth Y., De Ridder J., Mosser B., Garcia R.A., Kallinger T., Mathur S., Huber D., Buzasi D.L., Preston H.L., Hale S.J., Ballot J., Chaplin W.J., Regulo C., Bedding T.R., Stello D., Borucki W.J., Koch D.G., Jenkins J., Allen C., Gilliland R.L., Kjeldsen H., Christensen-Dalsgaard J. <Astron. Astrophys., 525, A131 (2011)> =2011A&A...525A.131HADC_Keywords: Stars, giant ; Stars, late-type ; PhotometryKeywords: asteroseismology - stars: late-type - methods: observational - techniques: photometricAbstract: The large number of stars for which uninterrupted high-precision photometric timeseries data are being collected with Kepler and CoRoT initiated the development of automated methods to analyse the stochastically excited oscillations in main-sequence, subgiant and red-giant stars. We investigate the differences in results for global oscillation parameters of G and K red-giant stars due to different methods and definitions. We also investigate uncertainties originating from the stochastic nature of the oscillations.Description: For this investigation we use Kepler data obtained during the first four months of operation. These data have been analysed by different groups using already published methods and the results are compared. We also performed simulations to investigate the uncertainty on the resulting parameters due to different realizations of the stochastic signal.File Summary:

FileName Lrecl Records Explanations

ReadMe 80 . This file table7.dat 93 1295 Results for numax and Dnu from different methods

See also: V/133 : Kepler Input Catalog (Kepler Mission Team, 2009) J/A+A/399/271 : Oscillations in the PMS star V346 Ori (Pinheiro+, 2003) J/A+A/406/L23 : Solar-like oscillations in alpha Cen B (Carrier+, 2003) J/A+A/506/465 : Solar-like oscillations in red giants (Hekker+, 2009)Byte-by-byte Description of file: table7.dat

Bytes Format Units Label Explanations

1- 8 I8 --- KIC Star KIC (Cat. V/133) number 10- 15 F6.2 uHz nu1 ? COR frequency of maximum oscillation power (1) 17- 21 F5.2 uHz Dnu1 ? COR large frequency separation (1) 23- 28 F6.2 uHz nu2 ? CAN frequency of maximum oscillation power (1) 30- 34 F5.2 uHz Dnu2 ? CAN large frequency separation (1) 36- 41 F6.2 uHz nu3 ? A2Z frequency of maximum oscillation power (1) 43- 47 F5.2 uHz Dnu3 ? A2Z large frequency separation (1) 49- 54 F6.2 uHz nu4 ? SYD frequency of maximum oscillation power (1) 56- 60 F5.2 uHz Dnu4 ? SYD large frequency separation (1) 62- 67 F6.2 uHz nu5 ? DLB frequency of maximum oscillation power (1) 69- 73 F5.2 uHz Dnu5 ? DLB large frequency separation (1) 75- 80 F6.2 uHz nu6 ? OCTI frequency of maximum oscillation power (1) 82- 87 F6.2 uHz nu7 ? OCTII frequency of maximum oscillation power (1) 89- 93 F5.2 uHz Dnu6 ? OCT large frequency separation (1)

Note (1): Methods used: * COR: autocorrelation method described by Mosser & Appourchaux (2009A&A...508..877M). numax is obtained as the centroid of a Gaussian fit to the smoothed power spectrum. For the smoothing, a Gaussian with full width half maximum (FWHM) of 3<Dnu> is used. <Dnu> is determined from the first peak in the autocorrelation of the timeseries apodised with a Hanning filter, where the FWHM of the excess envelope is used to compute the mean value. * CAN: automated Bayesian Markov-Chain Monte Carlo algorithm (Kallinger et al. 2010A&A...509A..77K; Gruberbauer et al. 2009A&A...506.1043G). numax is defined as the centroid of a Gaussian fitted to the unsmoothed power spectrum. <Dnu> is obtained from peakbagging, i.e. from fitting a sequence of Lorentzian profiles spanning three radial orders to the background-corrected power spectrum, parameterised by the large and small frequency separations. * A2Z: method described by Mathur et al. (2010A&A...511A..46M) and adapted for the analysis of red giants, numax is defined from a Gaussian fit to the smoothed power spectrum. For the smoothing a boxcar of width 4 <Dnu> is used. <Dnu> is determined from the highest feature in the power spectrum of the power spectrum (PS@PS), which is computed over a range numax±numax/3. The results for <Dnu> are cross-checked with results from the autocorrelation method (Mosser & Appourchaux, 2009A&A...508..877M). * SYD: Huber et al. (2009, Commun. Asteroseismol., 160, 74) compute numax as the peak of the smoothed power spectrum. The smoothed power spectrum is computed using a Gaussian with a FWHM of 2 <Dnu>. <Dnu> is computed from the autocorrelation of the power spectrum in the frequency interval numax±5-7 <Dnu>_{exp}, where <Dnu>_{exp}is calculated using Eq. (2). * DLB: method of Buzasi, Preston, where numax is determined from a Gaussian fit to the smoothed power spectrum. The power spectrum is smoothed using a Gaussian filter with a width equal to 10uHz. <Dnu> is computed from the autocorrelation of the power spectrum in the range numax±numax/4. * OCT: method described by Hekker et al. (2010MNRAS.402.2049H) and adapted for red giants numax is determined in two ways. In the first method (OCT I), numax is defined as the centroid of a Gaussian fit to the smoothed power spectrum. In the second method (OCT II), numax is computed as the first moment of the area under the smoothed power envelope. The smoothing is obtained using a boxcar with a width of 2<Dnu>. <Dnu> is computed from the power spectrum of the power spectrum (PS@PS) of the full frequency range in which oscillation excess has been detected.

History: From electronic version of the journal(End)Patricia Vannier [CDS] 16-May-2011

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