J/A+A/506/85 HD 50844 observed by CoRoT (Poretti+, 2009)
HD 50844: the new look of Delta Sct stars from CoRoT space photometry.
Poretti E., Michel E., Garrido R., Lefevre L., Mantegazza L., Rainer M.,
Rodriguez E., Uytterhoeven K., Amado J.P., Martin-Ruiz S., Moya A.,
Niemczura E., Suarez J.C., Zima W., Baglin A., Auvergne M., Baudin F.,
Catala C., Samadi R., Alvarez M., Mathias P., Paparo M., Papics P.,
Plachy E.
<Astron. Astrophys. 506, 85 (2009)>
=2009A&A...506...85P 2009A&A...506...85P
ADC_Keywords: Stars, variable ; Stars, F-type ; Spectroscopy
Keywords: stars: variables: delta Sct - stars: oscillations - stars: interiors -
stars: individual: HD 50844
Abstract:
This work presents the results obtained on HD 50844, the only delta
Sct star observed in the CoRoT Initial Run (57.6d). The aim of these
CoRoT observations was to investigate and characterize for the first
time the pulsational behaviour of a delta Sct star, when observed at a
level of precision and with a much better duty cycle than from the
ground. The 140016 datapoints were analysed using independent
approaches (SigSpec software and different iterative sine-wave
fittings) and several checks performed (splitting of the timeseries in
different subsets, investigation of the residual light curves and
spectra. A level of 10-5mag was reached in the amplitude spectra of
the CoRoT timeseries. The space monitoring was complemented by
ground-based high-resolution spectroscopy, which allowed the mode
identification of 30 terms. The frequency analysis of the CoRoT
timeseries revealed hundreds of terms in the frequency range
0-30d-1. All the cross-checks confirmed this new result. The initial
guess that delta Sct stars have a very rich frequency content is
confirmed. The spectroscopic mode identification gives theoretical
support since very high-degree modes (up to ell=14) are identified. We
also prove that cancellation effects are not sufficient in removing
the flux variations associated to these modes at the noise level of
the CoRoT measurements.
The ground-based observations indicate that HD 50844 is an evolved
star that is slightly underabundant in heavy elements, located on the
Terminal Age Main Sequence. Probably due to this unfavourable
evolutionary status, no clear regular distribution is observed in the
frequency set. The predominant term f1=6.92d-1 has been identified
as the fundamental radial mode combining ground-based photometric and
spectroscopic data. The CoRoT scientific programme contains other
delta Sct stars, with different evolutionary statuses. The very rich
and dense frequency spectrum discovered in the light curve of HD 50844
is the starting point for future investigations.
Description:
We compared the results from SigSpec and from the iterative-sine-wave
fitting, considering an error range of 0.005d-1 in frequency (i.e.,
a width 3.4 times narrower than 1/DeltaT).
The cross-checks show an almost complete agreement on the values of
the first 500 frequencies: 498 frequencies were found by both methods,
whose 438 (88%) have an amplitude within the 20% range of tolerance.
In particular, both methods correctly identified the first 462
frequencies within an interval of few units of 10-4d-1. These
frequencies are listed in Table 2.
Objects:
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RA (2000) DE Designation(s)
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06 54 50.1 -01 04 15 HD 50844 = 2MASS J06545011-0104148
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 23 462 Frequencies and amplitudes of the first 462
terms identified in the CoRoT data in 17 clusters
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See also:
B/corot : CoRoT observation log (CoRoT, 2009)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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2- 11 F10.7 d-1 Freq Frequency in cycles/day
15- 23 F9.6 mmag Amp Amplitude in millimag
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Acknowledgements:
Ennio Poretti,
References:
Reegen, 2007A&A...467.1353R 2007A&A...467.1353R, SigSpec. I. Frequency- and phase-resolved
significance in Fourier space.
Vanicek, 1971Ap&SS..12...10V 1971Ap&SS..12...10V, Further Development and Properties of the
Spectral Analysis by Least-Squares
(End) Ennio Poretti [INAF-OA Brera, Italy], Patricia Vannier [CDS] 13-Jun-2009