J/A+A/453/309 HARPS observations of nine galactic Cepheids (Nardetto+, 2006)
High resolution spectroscopy for Cepheids distance determination.
I. Line asymmetry.
Nardetto N., Mourard D., Kervella P., Mathias P., Merand A., Bersier D.
<Astron. Astrophys., 453, 309-319 (2006)>
=2006A&A...453..309N 2006A&A...453..309N
ADC_Keywords: Stars, variable ; Spectroscopy ; Radial velocities
Keywords: techniques: spectroscopic - stars: atmospheres - stars: oscillations -
stars: variables: Cepheids - stars: distances
Abstract:
The ratio of pulsation to radial velocity (the projection factor) is
currently limiting the accuracy of the Baade-Wesselink method, and in
particular of its interferometric version recently applied to several
nearby Cepheids.
This work aims at establishing a link between the line asymmetry
evolution over the Cepheids' pulsation cycles and their projection
factor, with the final objective to improve the accuracy of the
Baade-Wesselink method for distance determinations.
We present HARPS high spectral resolution observations (R=120000) of
nine galactic Cepheids: R Tra, S Cru, Y Sgr, beta Dor, zeta Gem,
Y Oph, RZ Vel, l Car and RS Pup, having a good period sampling
(P=3.39d to P=41.52d). We fit spectral line profiles by an asymmetric
bi-Gaussian to derive radial velocity, Full-Width at Half-Maximum in
the line (FWHM) and line asymmetry for all stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 51 9 Observed sample of Cepheids (sorted by
increasing period)
table345.dat 101 126 HARPS observations results
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name
10- 15 I6 --- HD HD number
17- 26 F10.7 d Per Pulsation period (1)
28- 39 F12.4 d T0 Reference Julian date (1)
41- 43 I3 --- Nsp Number of spectra
45- 46 I2 --- Nc Number of cycles
48- 51 F4.2 mag Vmag Visible magnitude from Berdnikov et al.
(2000, Cat. J/A+AS/143/211
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Note (1): For l Car, the reference Julian date (T0) and the pulsation period (P)
used to compute the phase are from Szabados (1989ApJ...337L..29S 1989ApJ...337L..29S).
For others stars we used ephemeris from Berdnikov et al.
(2001JAD.....7....3B 2001JAD.....7....3B).
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Byte-by-byte Description of file: table345.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name
10- 19 F10.2 d JD Average Julian data of observation
21- 24 F4.2 --- Phase Average pulsation phase of observation.
For ephemeris, see the Paper
26- 27 I2 --- Cycle Pulsating cycle of the star corresponding
to observation
29 I1 --- NSpec Number of spectra associated to observation (1)
31- 36 F6.2 km/s RVg Gaussian fit radial velocity
38- 41 F4.2 km/s e_RVg rms uncertainty on RVg
43- 48 F6.2 km/s RVm Minimum radial velocity (2)
50- 53 F4.2 km/s e_RVm rms uncertainty on RVm
55- 60 F6.2 km/s RVc Radial velocity corresponding to the first
moment of the spectral line
62- 65 F4.2 km/s e_RVc rms uncertainty on RVc
67- 71 F5.3 0.1nm FWHM Full-Width at Half Maximum (2)
73- 77 F5.3 0.1nm e_FWHM rms uncertainty to FWHM
79- 82 F4.2 --- D Line depth. Uncertainties are of about 10-4 (2)
84- 88 F5.1 % A Asymmetry (2)
90- 92 F3.1 % e_A Uncertainty corresponding to the asymmetry
94- 96 I3 --- SNR Observational spectral line signal to noise ratio
98-101 F4.1 --- Chi2 Reduced Chi2 factor corresponding to the
bi-Gaussian fit
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Note (1): Results corresponding to these spectra are averaged.
Note (2): Quantity derived from a bi-Gaussian fit. See paper for more detail.
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Acknowledgements: N. Nardetto, nardetto(at)mpifr-bonn.mpg.de
References:
Nardetto et al., Paper II 2007A&A...471..661N 2007A&A...471..661N
(End) Patricia Vannier [CDS] 16-Aug-2007