J/MNRAS/482/616 Detecting solar-like oscillations (Bell+, 2019)
Coefficients of variation for detecting solar-like oscillations.
Bell K.J., Hekker S., Kuszlewicz J.S.
<Mon. Not. R. Astron. Soc., 482, 616-625 (2019)>
=2019MNRAS.482..616B 2019MNRAS.482..616B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Spectra, infrared
Keywords: methods: data analysis - methods: statistical - stars: oscillations
Abstract:
Detecting the presence and characteristic scale of a signal is a
common problem in data analysis. We develop a fast statistical test of
the null hypothesis that a Fourier-like power spectrum is consistent
with noise. The null hypothesis is rejected where the local
'coefficient of variation' (CV) - the ratio of the standard deviation
to the mean - in a power spectrum deviates significantly from
expectations for pure noise (CV∼1.0 for a Χ2-degrees-of-freedom
distribution). This technique is of particular utility for detecting
signals in power spectra with frequency-dependent noise backgrounds,
as it is only sensitive to features that are sharp relative to the
inspected frequency bin width. We develop a CV-based algorithm to
quickly detect the presence of solar-like oscillations in photometric
power spectra that are dominated by stellar granulation. This approach
circumvents the need for background fitting to measure the frequency
of maximum solar-like oscillation power, νmax. In this paper, we
derive the basic method and demonstrate its ability to detect the
pulsational power excesses from the well-studied APOKASC-2 sample of
oscillating red giants observed by Kepler. We recover the catalogued
νmax values with an average precision of 2.7 per cent for 99.4
per cent of the stars with 4yr of Kepler photometry. Our method
produces false positives for <1 per cent of dwarf stars with νmax
well above the long-cadence Nyquist frequency. The algorithm also
flags spectra that exhibit astrophysically interesting signals in
addition to single solar-like oscillation power excesses, which we
catalogue as part of our characterization of the Kepler light curves
of APOKASC-2 targets.
Description:
we use a CV-based strategy for detecting solar-like oscillations in
red giants and measuring νmax. The following method is
specifically designed for long-cadence Kepler light curves. It is
validated by null results for dwarf stars with super-Nyquist
νmax>500µHz, and by our recovery of catalogued νmax
values for the APOKASC giants. The second APOKASC catalogue
(APOKASC-2; Pinsonneault et al. 2018ApJS..239...32P 2018ApJS..239...32P, Cat.
J/ApJS/239/32) characterizes 6676 evolved stars with both Kepler light
curves and APOGEE spectra (Pinsonneault et al. 2014ApJS..215...19P 2014ApJS..215...19P,
Cat. J/ApJS/215/19). It includes νmax values combined from an
ensemble of pipelines. We use these as a benchmark for evaluating the
sensitivity, accuracy, and precision of our method of detecting
νmax from CV spectra.
Our νmax measurements from the CV spectra of the full sample of
6656 APOKASC-2 stars with KASOC data are tabulated in Table A1. We
also catalogue the associated flags and emphasize that the vast
majority of our νmax values are robust, even when accompanied by
flags.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 40 6756 CV-based νmax measurements for 6656 giants
in APOKASC
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- ID Star name (KIC NNNNNNNN)
14- 20 F7.3 uHz numaxmeas ? Frequency of maximum solar-like oscillation
power measured by the coefficient of
variation (CV) algorithm
22- 28 F7.3 uHz numaxcat ? Frequency of maximum solar-like oscillation
power from APOKASC-2 (Pinsonneault et al.
2018ApJS..239...32P 2018ApJS..239...32P)
30- 37 F8.3 uHz numaxFliPer Frequency of maximum solar-like oscillation
power from FliPer (Bugnet et al.
2017sf2a.conf...85B)
39- 40 I2 --- f_numaxmeas Flag on numaxmeas (1)
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Note (1): The binary bit flags returned by our algorithm are summed and
presented in this column. The individual flags are coded as follows:
1 = Additional significant, independent CVs
2 = CV spike exceeds solar-like expectation
4 = More than one numax candidate detected
8 = FliPer numax disagreement
16 = numax candidate near Nyquist frequency
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 22-Jun-2022