Cepheid distances from infrared long-baseline interferometry

Kervella, P.; Nardetto, N.; Bersier, D.; Mourard, D.; Foresto, V. Coudé du

doi:10.1051/0004-6361:20031743

Cited by 104 publications

(137 citation statements)

References 64 publications

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“…The same limitation was also found by Kervella et al (2004) using interferometric data collected with VINCI at VLTI. We therefore only computed a mean physical radius of 53 ± 3 R by adopting the trigonometric parallax of 3.0 ± 0.18 mas from the HST (Benedict et al 2007).…”

Section: Angular Diametersupporting

confidence: 74%

“…Following Kervella et al (2004), we adopted the limb darkening (LD) intensity profile by Claret (2000). The radius r 1 only depends on the mean value of each visibility spectrum ( V 2 (λ) ), whose error bar we computed as the quadratic sum of the weighted average error plus the correlated component due to the TF variation 2 .…”

Section: Angular Diametermentioning

confidence: 99%

“…We therefore only computed a mean physical radius of 53 ± 3 R by adopting the trigonometric parallax of 3.0 ± 0.18 mas from the HST (Benedict et al 2007). In Table 3 we compared it with recent estimates from both optical interferometry (Kervella et al 2004) and InfraRed Surface Brightness (IRSB, Groenewegen, priv. comm.…”

Section: Angular Diametermentioning

confidence: 99%

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On the binarity of the classical Cepheid X Sagittarii from interferometric observations

Causi

Antoniucci

Bono

et al. 2012

A&A

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Context. Optical-infrared interferometry can provide direct geometrical measurements of the radii of Cepheids and/or reveal any unknown binary companions of these stars. Such information is very important for properly calibrating the period-luminosity relations and determining binary fraction among Cepheids. Aims. We observed the Cepheid X Sgr with VLTI/AMBER in order to confirm or disprove the presence of the hypothesized binary companion and to directly measure the mean stellar radius, possibly detecting its variation along the pulsation cycle. Methods. From AMBER observations in MR mode, we performed a binary model fitting on the closure phase and a limb-darkened model fitting on the visibility. Results. Our analysis indicates that there is a point-like companion at a separation of 10.7 mas, which is 5.6 mag K fainter than the primary and whose flux and position are sharply constrained by the data. The radius pulsation is not detected, whereas the average limb-darkened diameter results in 1.48±0.08 mas, corresponding to 53 ± 3 R at a distance of 333.3 pc.

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Section: Angular Diametersupporting

confidence: 74%

Section: Angular Diametermentioning

confidence: 99%

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On the binarity of the classical Cepheid X Sagittarii from interferometric observations

Causi

Antoniucci

Bono

et al. 2012

A&A

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“…Although we are not interested here in an unbiased estimate of the angular diameter θ LD , the best-fit values of θ LD ( Car) = 2.92 mas is only 2% smaller than the mean angular diameter of θ LD ( Car) = 2.99 ± 0.01 mas measured by Kervella et al (2004c) in the K band. For RS Pup, the agreement between the present best-fit value of θ LD (RS Pup) = 0.93 mas and the 1.02 mas prediction by Moskalik & Gorynya (2006) is also reasonably good.…”

Section: Spectral Energy Distributionmentioning

confidence: 71%

“…The best-fit effective temperatures T eff of Car and RS Pup are respectively 4860 K and 5040 K. One should note however that there is a correlation between T eff and the angular diameter in this fit. Following Kervella et al (2004c), we consider an effective gravity of log g = 1.5, typical of a long period Cepheid, but changing this parameter by ±1.0 dex does Table 5. Overview of the infrared photometry of Car and RS Pup from the present work and bibliography.…”

Section: Spectral Energy Distributionmentioning

confidence: 99%

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

Kervella¹,

Mérand

Gallenne

2009

A&A

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Context. Compact circumstellar envelopes (CSEs) have been detected around several Cepheids by interferometry. In particular, observations with the VINCI instrument revealed in 2006 a compact envelope around the long period Cepheid Car (P = 35.5 days). Another Cepheid, RS Pup (P = 41.4 days), presents a large (≈2 ) circumstellar nebula scattering the Cepheid light in the visible. These envelopes are particularly interesting for two reasons: their presence could impact the Cepheid distance scale, and they could imply stellar mass loss. Aims. Our goal is to establish the spatial and spectral properties of the CSEs of Car and RS Pup. This is done through a parametrization of the envelopes in terms of fractional flux (with respect to the star) and angular size. Methods. We retrieved archival Spitzer images of the two stars (λ = 3.5−70 μm), and obtained new diffraction-limited imaging with the VLT/VISIR camera in BURST mode (λ = 8.6−11.9 μm), as well as interferometric observations with the VLTI/MIDI beam combiner (λ = 8−13 μm). This combination of single-telescope and interferometric techniques allows us to probe the envelopes of the two Cepheids over a broad range of angular scales, from arcminutes to milliarcseconds. Results. The circumstellar envelope of RS Pup is resolved spatially at 24 and 70 μm by Spitzer, and around 10 μm by MIDI and VISIR. The envelope of Car appears much more compact, and is resolved only in the VISIR and MIDI observations. The infrared excesses we detect around RS Pup and Car are both very significant, but differ considerably in spectral and spatial properties. We detect a warm component in the CSE of both stars at a spatial scale of a few 100 to a few 1000 AU. In addition, RS Pup presents a very large (several 100 000 AU) and cold (≈40 K) dusty envelope. Conclusions. The observed properties of the CSEs lead us to propose that the cold dust content of the large reflection nebula surrounding RS Pup has an interstellar origin, while the warm CSEs of the two stars were created by ongoing stellar mass loss. We also speculate that the NGC 7023 reflection nebula surrounding the Herbig Be star HD 200775 is an analogue of RS Pup at an age of 100 000 years. The presence of CSEs around the two brightest long-period Cepheids is an indication that many long-period members of this class, if not all, could be surrounded by warm circumstellar envelopes created by mass loss. However, very large dusty envelopes such as that of RS Pup are probably less common, as according to our scenario, they require the presence of a high dust density in the interstellar medium (ISM) at the time of the formation of the Cepheid progenitor.

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VLTI Science Highlights

Perrin

2009

Astrophysics and Space Science Proceedings

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Cepheid distances from infrared long-baseline interferometry

Cited by 104 publications

References 64 publications

On the binarity of the classical Cepheid X Sagittarii from interferometric observations

On the binarity of the classical Cepheid X Sagittarii from interferometric observations

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

VLTI Science Highlights

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