The orbit and companions of the classical Cepheid FF AQL

Evans, Nancy Remage; Welch, D. L.; Scarfe, C. D.; Teays, T. J.

doi:10.1086/115442

Cited by 24 publications

(27 citation statements)

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“…From IUE spectra, Evans et al (1990) detected around FF Aql a companion with a spectral type between A9 V and F3 V. This corresponds to a magnitude difference with respect to the Cepheid ΔK ∼ 6.1-6.5 mag. Evans (1992) found that the companion of T Vul is a A0.8 V star, also estimated from IUE spectra, and corresponds to a magnitude difference ΔK ∼ 5.2 mag.…”

Section: Introductionmentioning

confidence: 93%

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Mean angular diameters, distances, and pulsation modes of the classical Cepheids FF Aquilae and T Vulpeculae

Gallenne¹,

Kervella²,

Mérand³

et al. 2012

A&A

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We report the first angular diameter measurements of two classical Cepheids, FF Aql and T Vul, that we obtain using observations with the FLUOR instrument installed at the CHARA interferometric array. We derive average limb-darkened angular diameters of θ LD = 0.878 ± 0.013 mas and θ 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 R and R = 35.6± 4.4 R , 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 this pulsation mode is of prime importance to calibrating the period-luminosity relation with a uniform sample of fundamental mode Cepheids.

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Section: Introductionmentioning

confidence: 93%

“…Among the published radial velocity data of FF Aql, we chose Evans et al (1990) for two reasons. First, the orbital motion caused by the presence of the companion had already been removed from measurements, leaving only the displacement due to the pulsating photosphere.…”

Section: Radial Velocity Integrationsmentioning

confidence: 99%

Mean angular diameters, distances, and pulsation modes of the classical Cepheids FF Aquilae and T Vulpeculae

Gallenne¹,

Kervella²,

Mérand³

et al. 2012

A&A

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“…For most of the known spectroscopic binaries the derived orbital parameters are close to literature values, cf. Evans et al (1990) for FF Aql, Imbert (1996) for Z Lac and U Vul, Evans et al (1999) for T Mon, Petterson et al (2004) for S Mus and V350 Sgr, Benedict et al (2007) for W Sgr, Gorynya et al (1995) for S Sge, Evans (1988) for SU Cyg. The only exceptions are VZ Cyg and SU Cas.…”

Section: Binary Cepheidsmentioning

confidence: 99%

Baade-Wesselink distances and the effect of metallicity in classical cepheids

Groenewegen

2008

A&A

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Context. The metallicity dependence of the Cepheid PL-relation is of importance in establishing the extra-galactic distance scale. Aims. The aim of this paper is to investigate the metallicity dependence of the PL-relation in V and K based on a sample of 68 Galactic Cepheids with individual Baade-Wesselink distances (some of the stars also have an HST-based parallax) and individually determined metallicities from high-resolution spectroscopy. Methods. Literature values of the V-band, K-band and radial velocity data have been collected for a sample of 68 classical cepheids that have their metallicity determined in the literature from high-resolution spectroscopy. Based on a (V − K) surface-brightness relation and a projection factor derived in a previous paper, distances have been derived from a Baade-Wesselink analysis. PL-and PLZ-relations in V and K are derived. Results. The effect of the adopted dependence of the projection factor on period is investigated. The change from a constant p-factor to one recently suggested in the literature with a mild dependence on log P results in a less steep slope by 0.1 unit, which is about the 1-sigma error bar in the slope itself. The observed slope in the PL-relation in V in the LMC agrees with both hypotheses. In K the difference between the Galactic and LMC slope is larger and would favour a mild period dependence of the p-factor. The dependence on metallicity in V and K is found to be marginal, and independent of the choice of p-factor on period. This result is severely limited by the small range in metallicity covered by the Galactic Cepheids.

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“…The present study makes use of the following references providing RV data: Anderson (2014), Barnes et al (2005), Bersier et al (1994b), Bersier (2002), Evans et al (1990), Gorynya et al (1998), Kiss (1998), Nardetto et al (2009), Petterson et al (2005, and Storm et al (2011).…”

Section: Radial Velocity Measurements From the Literaturementioning

confidence: 99%

“…The signature of orbital motion is clearly apparent in the RV curve, and was extensively studied by Evans et al (1990). We corrected all the data used in the present study (Evans et al 1990;Gorynya et al 1998;Kiss 1998)) with a modified version of the Wright & Howard formalism (Wright & Howard 2009), in which we included the pulsation of the star (see Gallenne et al 2013b). We solved for the spectroscopic orbital elements and pulsation parameters with uncertainties derived via the bootstrapping technique (with replacement and 10 000 bootstrap samples).…”

Section: Ff Aqlmentioning

confidence: 99%

Observational calibration of the projection factor of Cepheids

Breitfelder

Mérand

Kervella

et al. 2016

A&A

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Context. The distance to pulsating stars is classically estimated using the parallax-of-pulsation (PoP) method, which combines spectroscopic radial velocity (RV) measurements and angular diameter (AD) estimates to derive the distance of the star. A particularly important application of this method is the determination of Cepheid distances in view of the calibration of their distance scale. However, the conversion of radial to pulsational velocities in the PoP method relies on a poorly calibrated parameter, the projection factor (p-factor). Aims. We aim to measure empirically the value of the p-factors of a homogeneous sample of nine bright Galactic Cepheids for which trigonometric parallaxes were measured with the Hubble Space Telescope (HST) Fine Guidance Sensor. Methods. We use the SPIPS algorithm, a robust implementation of the PoP method that combines photometry, interferometry, and radial velocity measurements in a global modeling of the pulsation of the star. We obtained new interferometric angular diameter measurements using the PIONIER instrument at the Very Large Telescope Interferometer (VLTI), completed by data from the literature. Using the known distance as an input, we derive the value of the p-factor of the nine stars of our sample and study its dependence with the pulsation period. Results. We find the following p-factors: p = 1.20 ± 0.12 for RT Aur, p = 1.48 ± 0.18 for T Vul, p = 1.14 ± 0.10 for FF Aql, p = 1.31 ± 0.19 for Y Sgr, p = 1.39 ± 0.09 for X Sgr, p = 1.35 ± 0.13 for W Sgr, p = 1.36 ± 0.08 for β Dor, p = 1.41 ± 0.10 for ζ Gem, and p = 1.23 ± 0.12 for Car. Conclusions. The values of the p-factors that we obtain are consistently close to p = 1.324 ± 0.024. We observe some dispersion around this average value, but the observed distribution is statistically consistent with a constant value of the p-factor as a function of the pulsation period (χ 2 = 0.669). The error budget of our determination of the p-factor values is presently dominated by the uncertainty on the parallax, a limitation that will soon be waived by Gaia.

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The orbit and companions of the classical Cepheid FF AQL

Cited by 24 publications

References 0 publications

Mean angular diameters, distances, and pulsation modes of the classical Cepheids FF Aquilae and T Vulpeculae

Mean angular diameters, distances, and pulsation modes of the classical Cepheids FF Aquilae and T Vulpeculae

Baade-Wesselink distances and the effect of metallicity in classical cepheids

Observational calibration of the projection factor of Cepheids

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