J/A+A/533/A4 CoRoT photometry of three O-type stars (Blomme+, 2011)
Variability in the CoRoT photometry of three hot O-type stars.
HD 46223, HD 46150 and HD 46966
Blomme R., Mahy L., Catala C., Cuypers J., Gosset E., Godart M.,
Montalban J., Ventura P., Rauw G., Morel T., Degroote P., Aerts C.,
Noels A., Michel E., Baudin F., Baglin A., Auvergne M., Samadi R.
<Astron. Astrophys. 533, A4 (2011)>
=2011A&A...533A...4B 2011A&A...533A...4B
ADC_Keywords: Stars, O ; Photometry
Keywords: stars: variables: general - stars: early-type -
stars: oscillations - stars: individual: HD 46223 -
stars: individual: HD 46150 - stars: individual: HD 46966
Abstract:
The detection of pulsational frequencies in stellar photometry is
required as input for asteroseismological modelling. The second short
run (SRa02) of the CoRoT mission has provided photometric data of
unprecedented quality and time-coverage for a number of O-type stars.
We analyse the CoRoT data corresponding to three hot O-type stars,
describing the properties of their light curves and we search for
pulsational frequencies, which we then compare to theoretical model
predictions. We determine the amplitude spectrum of the data, using
the Lomb-Scargle and a multifrequency HMM-like technique. Frequencies
are extracted by prewhitening, and their significance is evaluated
under the assumption that the light curve is dominated by red noise.
We search for harmonics, linear combinations and regular spacings
among these frequencies. We use simulations with the same time
sampling as the data as a powerful tool to judge the significance
of our results. From the theoretical point of view, we use the MAD
non-adiabatic pulsation code to determine the expected frequencies of
excited modes. A substantial number of frequencies is listed, but none
can be convincingly identified as being connected to pulsations. The
amplitude spectrum is dominated by red noise. Theoretical modelling
shows that all three O-type stars can have excited modes but the
relation between the theoretical frequencies and the observed spectrum
is not obvious. The dominant red noise component in the hot O-type
stars studied here clearly points to a different origin than the
pulsations seen in cooler O stars. The physical cause of this red
noise is unclear, but we speculate on the possibility of sub-surface
convection, granulation, or stellar wind inhomogeneities being
responsible.
Description:
We use a prewhitening technique to analyse the CoRoT photometry,
and list the frequencies, semi-amplitudes and phases (with their
respective error bars). The phases are defined with t=0 corresponding
to the first non-flagged data point. We also list the standard
deviation at each stage in the prewhitening and the significance of
the frequency under the assumption of red noise. Red-noise significant
frequencies are noted as well as those frequencies that remain present
if we split the data set in two halves.
Objects:
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RA (2000) DE Designation(s) (file)
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06 32 09.3 +04 49 25 HD 46223 = HIP 31149 (hd46223.dat)
06 31 55.5 +04 56 34 HD 46150 = HIP 31130 (hd46150.dat)
06 36 25.9 +06 04 59 HD 46966 = HIP 31567 (hd46966.dat)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
hd46223.dat 74 500 Frequencies, amplitudes, phases for HD 46223
(table 2 of the paper)
hd46150.dat 74 500 Frequencies, amplitudes, phases for HD 46150
(table 3 of the paper)
hd46966.dat 74 300 Frequencies, amplitudes, phases for HD 46966
(table 4 of the paper)
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See also:
B/corot : CoRoT observation log Release 7 (CoRoT, 2010)
Byte-by-byte Description of file: hd46150.dat hd46223.dat hd46966.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID Frequency ID (running number)
6- 12 F7.4 d-1 Freq Frequency
14- 20 F7.4 d-1 e_Freq Error on the frequency
22- 29 F8.3 ct Ampl Semi-amplitude
31- 38 F8.3 ct e_Ampl Error on semi-amplitude
40- 45 F6.3 rad Phase Phase
47- 52 F6.3 rad e_Phase Error on the phase
54- 62 F9.3 ct Stdev Standard deviation at this phase prewhitening
65- 70 F6.4 --- SigRed Significance under red noise conditions
72 A1 --- Red [R] 'R' if significant under red noise,
' ' otherwise
74 A1 --- Half [*] '*' if still present when data set is split
in two halves, ' ' otherwise
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Acknowledgements:
Ronny Blomme, Ronny.Blomme(at)oma.be
(End) Ronny Blomme [ROB, Belgium], Patricia Vannier [CDS] 02-Jul-2011