tokens: in Appendix B . The final result is plotted in Fig. 5 and the derived parameters are listed in Table 5 . The final rms is small with only 90 m s −1 . Our revised orbital parameters are in rather good agreement with the literature, within 1.5 σ ( Groenewegen 2013 ; Gorynya et al. 1995 ; Evans et al. 1990 ; Abt 1959 ). Fig. 5. Result of our combined fit of the orbital and radial pulsation velocity for FF Aql. Left panel : fitted (solid lines) and measured primary (blue dots) orbital velocity. Right panel : fitted (solid line) and measured (blue dots) radial pulsation velocity. Table 5. Pulsation and orbital parameters of the FF Aql system. Notes. Parameters are the same as in Table 4 . a 1 : semi-major axis of the Cepheid’s orbit relative to the centre of mass. f ( M ): the mass function. (a) Not fitted. (b) Uncertainty not given by the authors. (c) Gorynya et al. (1995) . We noticed a slight difference in the systemic velocity between our estimate and that from Gorynya et al. (1995) . This might be linked to the wide companion, however, this might also be from other non-astrophysical effects. We should be cautious when studying long-term variations of v γ , unless a clear pattern is observed. Differences in v γ of the order of 0.5–1 km s −1 might be caused, for instance, to the way RVs are determined (cross-correlation, bisector, ...), the mask used, and the instrument zero points. In this paper we did not perform such a long-term study as this is out of the scope of this paper and would require a complete analysis of all available literature data. U Car. The companion orbiting this Cepheid is below our detection level. Our datasets enable us however to exclude any companion with a flux ratio higher than 0.4%, which would correspond to a spectral type earlier than B2V (see Table 3 ). Y Car. Our possibly detected companion has a flux ratio of ∼0.94% and would correspond to a ∼A0V spectral type, which is in rather good agreement with the ∼B9V derived by Evans (1992c) . Although additional data are still necessary to confirm, this possible detection seems in a very close orbit as we measured a projected separation of ∼2.5 mas (∼3.5 au), as for S Mus. We first estimated the 3 σ detection limit using all observables and removing the possible companion (because we have a detection), and second using only the CPs but without removing it (because there is no detection). We noticed that the closure phases alone provide a contrast limit lower than 4 mag (see Table 3 ), which explains the non-detection with only this observable. With all observables we add more constraints in this case, which provide contrast limit of 5 mag (5.1 mag within 25 mas). This enables us to exclude at 3 σ any companion with a spectral type earlier than A0V. YZ Car. The faint companion orbiting this Cepheid is not detected from our observations. Our 3 σ detection limits (see Table 3 ) show that any companion with a spectral type later than B3V would not have been detected with
ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O