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
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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 51 9 Observed sample of Cepheids (sorted by increasing period) table345.dat 101 126 HARPS observations results
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
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
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). For others stars we used ephemeris from Berdnikov et al. (2001JAD.....7....3B).
Byte-by-byte Description of file: table345.dat
Bytes Format Units Label Explanations
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
Note (1): Results corresponding to these spectra are averaged. Note (2): Quantity derived from a bi-Gaussian fit. See paper for more detail.
Acknowledgements: N. Nardetto, nardetto(at)mpifr-bonn.mpg.de References: Nardetto et al., Paper II 2007A&A...471..661N
(End) Patricia Vannier [CDS] 16-Aug-2007
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