Issue |
A&A
Volume 453, Number 1, July I 2006
|
|
---|---|---|
Page(s) | 155 - 162 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20054466 | |
Published online | 09 June 2006 |
Extended envelopes around Galactic Cepheids
II. Polaris and δ Cephei from near-infrared interferometry with CHARA/FLUOR
1
LESIA, UMR 8109, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France e-mail: antoine.merand@obspm.fr
2
Center for High Angular Resolution Astronomy, Georgia State University, PO Box 3965, Atlanta, Georgia 30302-3965, USA
3
National Optical Astronomy Observatories 950 North Cherry Avenue, Tucson, AZ 85719, USA
Received:
3
November
2005
Accepted:
11
March
2006
We present the results of long-baseline interferometric
observations of the classical Cepheids Polaris and δ Cep in the
near infrared K' band (1.9-2.3 μm), using the FLUOR instrument of
the CHARA Array. Following our previous detection of a circumstellar
envelope (CSE) around Car (Kervella et al. 2006), we report
similar detections around Polaris and δ Cep. Owing to the large
data set acquired on Polaris, in both the first and second lobes of
visibility function, we have detected the presence of a circum-stellar
envelope (CSE), located at
stellar radii, accounting for
% of the stellar flux in the K band. A similar model is
applied to the δ Cep data, which shows improved agreement
compared to a model without CSE. Finally, we find that the bias in
estimating the angular diameter of δ Cep in the framework of
the Baade-Wesselink method (Mérand et al 2005b) is of the order of
or less in the K band. A complete study of the influence of
the CSE is proposed in this context, showing that at the optimum
baseline for angular diameter variation detection, the bias is of the
order of the formal precision in the determination of the δ Cep
pulsation amplitude (
).
Key words: stars: variables: Cepheids / stars: circumstellar matter / stars: individual: Polaris (α Ursae Minoris) / stars: individual: δ Cephei / techniques: interferometric / techniques: high angular resolution
© ESO, 2006
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