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Post Info TOPIC: FF Aquilae
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RE: FF Aquilae
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Title: The Pulsation Mode and Distance of the Cepheid FF Aquilae
Authors: D. G. Turner, V. V. Kovtyukh, R. E. Luck, L. N. Berdnikov

The determination of pulsation mode and distance for field Cepheids is a complicated problem best resolved by a luminosity estimate. For illustration a technique based on spectroscopic luminosity discrimination is applied to the 4.47d s-Cepheid FF Aql. Line ratios in high dispersion spectra of the variable yield values of <Mv>=-3.40±0.02 s.e.(±0.04 s.d.), average effective temperature Teff=6195+-24 K, and intrinsic colour (<B>-<V>)o = +0.506±0.007, corresponding to a reddening of E(B-V)=0.25±0.01, or E(B-V)(B0)=0.26±0.01. The skewed light curve, intrinsic colour, and luminosity of FF Aql are consistent with fundamental mode pulsation for a small amplitude classical Cepheid on the blue side of the instability strip, not a sinusoidal pulsator. A distance of 413±14 pc is estimated from the Cepheid's angular diameter in conjunction with a mean radius of <R>=39.0±0.7 solar radii inferred from its luminosity and effective temperature. The dust extinction towards FF Aql is described by a ratio of total-to-selective extinction of Rv=Av/E(B-V)=3.16±0.34 according to the star's apparent distance modulus.

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Blobrana


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Title: Mean angular diameters, distances and pulsation modes of the classical Cepheids FF Aql and T Vul - CHARA/FLUOR near-infrared interferometric observations
Authors: A. Gallenne, P. Kervella, A. Mérand, H. McAlister, T. ten Brummelaar, V. Coudé du Foresto, J. Sturmann, L. Sturmann, N. Turner, C. Farrington, P. J. Goldfinger

We report the first angular diameter measurements of two classical Cepheids, FF Aql and T Vulpeculae, that we have obtained with the FLUOR instrument installed at the CHARA interferometric array. We obtain average limb-darkened angular diameters of \theta_LD = 0.878 ± 0.013 mas and \theta_LD = 0.629 ± 0.013 mas, respectively for FF Aql and T Vul. Combining these angular diameters with the HST-FGS trigonometric parallaxes leads to linear radii R = 33.6 ± 2.2 Rsol and R = 35.6 ± 4.4 Rsol, respectively. The comparison with empirical and theoretical Period-Radius relations leads to the conclusion that these Cepheids are pulsating in their fundamental mode. The knowledge of the pulsation mode is of prime importance to calibrate the Period-Luminosity relation with a uniform sample of fundamental mode Cepheids.

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