Journal Article

Observations of the pulsation of the Cepheid ℓ Car with the Sydney University Stellar Interferometer

J. Davis, A. P. Jacob, J. G. Robertson, M. J. Ireland, J. R. North, W. J. Tango and P. G. Tuthill

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 394, issue 3, pages 1620-1630
Published in print April 2009 | ISSN: 0035-8711
Published online April 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.14433.x
Observations of the pulsation of the Cepheid ℓ Car with the Sydney University Stellar Interferometer

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Observations of the southern Cepheid ℓ Car to yield the mean angular diameter and angular pulsation amplitude have been made with the Sydney University Stellar Interferometer at a wavelength of 696 nm. The resulting mean limb-darkened angular diameter is 2.990 ± 0.017 mas (i.e. ± 0.6 per cent) with a maximum-to-minimum amplitude of 0.560 ± 0.018 mas corresponding to 18.7 ± 0.6 per cent in the mean stellar diameter. Careful attention has been paid to uncertainties, including those in measurements, in the adopted calibrator angular diameters, in the projected values of visibility squared at zero baseline, and to systematic effects. No evidence was found for a circumstellar envelope at 696 nm. The interferometric results have been combined with radial displacements of the stellar atmosphere derived from selected radial velocity data taken from the literature to determine the distance and mean diameter of ℓ Car. The distance is determined to be 525 ± 26 pc and the mean radius 169 ± 8 R. Comparison with published values for the distance and mean radius shows excellent agreement, particularly when a common scaling factor from observed radial velocity to pulsation velocity of the stellar atmosphere (the p-factor) is used.

Keywords: techniques: interferometric; stars: distances; stars: individual: ℓ Car, HR 3884

Journal Article.  9583 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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