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. =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. -------------------------------------------------------------------------------- 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