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J/MNRAS/463/1707    l Car radial velocity curves              (Anderson, 2016)

Discovery of cycle-to-cycle modulated spectral line variability and velocity gradients in long-period Cepheids. Anderson R.I. <Mon. Not. R. Astron. Soc., 463, 1707-1739 (2016)> =2016MNRAS.463.1707A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Radial velocities Keywords: line: profiles - techniques: radial velocities - stars: individual: l Carinae = HD 84810 = HIP 47854 - stars: oscillations - stars: variables: Cepheids - distance scale Abstract: This work reports the discovery of cycle-to-cycle modulated spectral line and atmospheric velocity gradient variability in long-period Cepheids based on 925 high-resolution optical spectra of l Carinae (P∼35.5d) recorded during three heavy duty-cycle monitoring campaigns (in 2014, 2015, and 2016). Spectral line variability is investigated via cross-correlation functions (CCFs) computed using three sets of spectral lines (weak, solar, strong). A metallic line velocity gradient, δvr(t), is computed as the difference between weak and strong-line RVs. CCF shape indicators BIS (asymmetry), FWHM, and depth all exhibit clear phase-dependent variability patterns that differ from one pulsation cycle to the next. Weak-line CCFs exhibit these effects more clearly than strong-line CCFs. BIS exhibits the most peculiar modulated variability and can be used to identify the presence of cycle-to-cycle modulated line profile variations. δvr(t) clearly exhibits cycle-to-cycle differences that correlate very closely with modulated BIS variability, suggesting perturbations of the atmospheric velocity field as the cause for modulated spectral line variability. These perturbations are most significant during contraction and are not in phase with the pulsation, transmitting information between consecutive pulsation cycles. This work shows RV curve modulation to be a consequence of atmospheric velocity gradient perturbations. Possible origins of these perturbations and their impact on Cepheid RV measurements as well as the projection factor used in Baade-Wesselink-type distance determinations are discussed. Description: Line-of-sight (radial) velocities of the long-period classical Cepheid l Carinae were measured from 925 high-quality optical spectra recorded using the fiber-fed high-resolution (R∼60,000) Coralie spectrograph located at the Euler telescope at La Silla Observatory, Chile. The data were taken between 2014 and 2016. This is the full version of Tab. 2 presented partially in the paper. Line shape parameters (depth, width, asymmetry) are listed for the computed cross-correlation profiles (CCFs). Radial velocities were determined using different techniques (Gaussian, bi-Gaussian) and measured on CCFs computed using three different numerical masks (G2, weak lines, strong lines). Objects: ----------------------------------------------- RA (2000) DE Designation(s) ----------------------------------------------- 09 45 14.81 -62 30 28.5 l Car = = HD 84810 ----------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 93 925 Coralie radial velocities of l Carinae
See also: J/ApJ/824/1 : Timing data for the classical Cepheid l Car (Neilson+, 2016) J/MNRAS/455/4231 : Coralie radial velocities for l Car (Anderson+, 2016) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 12 F12.6 d BJD Barycentric Julian Date (BJD-2400000) 14- 17 F4.1 km/s FWHM FWHM of Gaussian fitted to CCF for G2 mask 19- 24 F6.3 km/s BIS CCF asymmetry parameter for G2 mask 26- 29 F4.1 % depth CCF contrast in percent for G2 mask 31- 37 F7.3 km/s RV Barycentric Gaussian RV for G2 mask 39- 43 F5.3 km/s e_RV Uncertainty on Gaussian RV for G2 mask 45- 51 F7.3 km/s RVbiG Barycentric bi-Gaussian RV for G2 mask 53- 59 F7.3 km/s RVw Barycentric Gaussian RV for weak lines 61- 65 F5.3 km/s e_RVw Uncertainty on Gaussian RV for weak lines 67- 72 F6.3 km/s BISw CCF asymmetry for weak lines 74- 80 F7.3 km/s RVs Barycentric Gaussian RV for strong lines 82- 86 F5.3 km/s e_RVs Uncertainty on Gaussian RV for strong lines 88- 93 F6.3 km/s BISs CCF asymmetry for strong lines
Acknowledgements: The assistance of many observers is acknowledged. RIA is grateful to the entire Euler team, the Geneva stellar variability group, and the Geneva exoplanet group for their assistance and support. The friendly and competent assistance by all ESO and non-ESO staff at La Silla Observatory was greatly appreciated. The Swiss Euler telescope is funded by the Swiss National Science Foundation. The ability to operate such long-term campaigns on a small telescope with high-quality instrumentation was crucial to this work's ability to illustrate the complex behaviour of Cepheid pulsations in this amount of detail. Richard I. Anderson, randerso(at)eso.org
(End) R. Anderson [Johns Hopkins Univ., USA], P. Vannier [CDS] 05-Feb-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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