Free Access
Volume 566, June 2014
Article Number L10
Number of page(s) 6
Section Letters
Published online 27 June 2014

Online material

Appendix A: Supporting figures

This appendix contains Figs. A.1A.3 that are analogous to Fig. 1. These figures unambiguously show the modulations discovered. The full dataset employed to create these figures is made publicly available through the CDS.

thumbnail Fig. A.1

New Coralie RV data for QZ Nor (N = 125). The large panel shows the phased RV curve, distinguishing data from different epochs by symbol style and color. The two right-hand panels provide close-ups around maximum (upper) and minimum RV (lower), and show the median RV uncertainty as a blue errorbar. The bottom panel shows residuals around an “average” Fourier series model fit to the combined data set (fit procedure described in Anderson et al. 2013).

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thumbnail Fig. A.2

Analogous to Fig. A.1 using RV data for V335 Puppis (N = 95).

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thumbnail Fig. A.3

Analogous to Fig. A.1 using RV data for RS Puppis (N = 439). RS Puppis also exhibits significant random cycle-to-cycle fluctuations in pulsation period (Berdnikov et al. 2009). As the close-up panels demonstrate, these random period fluctuations occur in addition to the modulation of the RV amplitude.

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Finally, Fig. A.4 shows the residuals of the models fit to the per-epoch data used to estimate the impact of modulation as a systematic uncertainty for Baade-Wesselink distances, cf. Table 1. The data were modeled as cubic splines for QZ Nor, Car, and RS Pup, and as a second-order Fourier series for the s-Cepheid V335 Pup.

thumbnail Fig. A.4

Fit residuals from the epochs (E1 and E2) used to estimate the impact on BW distances for all four Cepheids, cf. Table 1. For Car and RS Pup, both the cycle-to-cycle and longer timescales are shown. The earlier epoch is represented by green x markers, the later epoch by black open circles. For each epoch, the rms around the fit and median measurement uncertainty, σ, are printed in the corresponding panel, indicating excellent fits.

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© ESO, 2014

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