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J/A+A/528/A21        Echelle spectroscopy of δ Vel    (Pribulla+, 2011)

The nearby eclipsing stellar system delta Velorum. II. First reliable orbit for the eclipsing pair. Pribulla T., Merand A., Kervella P., Vanko M., Stevens I.R., Chini R., Hoffmeister V., Stahl O., Berndt A., Mugrauer M., Ammler-von Eiff M. <Astron. Astrophys. 528, A21 (2011)> =2011A&A...528A..21P
ADC_Keywords: Stars, nearby ; Binaries, eclipsing ; Spectroscopy Keywords: binaries: eclipsing - binaries: spectroscopic - stars: individual: HD 74956 (delta Velorum) Abstract: The nearby multiple system delta Velorum contains a widely detached eclipsing binary and a third component. We take advantage of this system offering the opportunity to determine the set of fundamental parameters (masses, luminosities, and radii) of three coeval stars with sufficient precision to test models of stellar evolution. Extensive high-resolution spectroscopy is analyzed by the broadening function technique to provide the first spectroscopic orbit of the eclipsing pair. Simultaneous analysis of the spectroscopic data and the SMEI satellite light curve is performed to provide astrophysical parameters for the components. We use a modified Roche model assuming an eccentric orbit and asynchronous rotation. The observations show that components of the eclipsing pair rotate at about two-thirds of the break-up velocity, which excludes any chemical peculiarity and results in a non-uniform surface brightness. Although the inner orbit is eccentric, no apsidal motion is seen during the SMEI photometric observations. For the inner orbit, the orbital parameters are eccentricity e=0.290, longitude of the periastron passage omega=109°, and inclination 89.0°. The component masses of M(Aa)=2.53±0.11M, M(Ab)=2.37±0.10M, and M(B)∼1.5M combined with the inferred radii of the Aa and Ab components indicate that the eclipsing pair has already left the main sequence and that the estimated age of the system is about 400Myr. Description: The most important dataset used to determine parameters of the eclipsing pair are 63 echelle spectra obtained at the Cerro Armazones Observatory, Chile. The spectra are wavelength-calibrated and normalized to the continuum. The barycentric correction was added. The names of the FITS files containing the spectra are encoded as, where "yymmdd" gives the evening date and "nn" is number of the spectrum within that night. Objects: ------------------------------------------------ RA (2000) DE Designation(s) ------------------------------------------------ 08 44 42.2 -54 42 32 HD 74956 = V* del Vel ------------------------------------------------ File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 40 63 Journal of spectroscopic observations at Cerro Armazones Observatory sp/* 0 63 FITS files of spectra
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 12 A12 --- FileName Name of the FITS spectrum in subdirectory sp 14- 24 F11.5 d BJD Baricentric Julian date of mid-exposure 26- 31 F6.4 --- Phase Phase of mid-exposure (1) 33- 35 I3 --- S/N Signal to noise ratio (2) 37- 40 I4 s ExpTime Exposure time
Note (1): Phases of mid-exposures were computed using the following ephemeris for the primary minimum: 2447832.0075+45.15023xE. Note (2): S/N ratio was estimated from line-free continuum close to MgII(4481) line.
Acknowledgements: Theodor Pribulla, Astron. Institute, Slovak Academy of Sciences, pribulla(at)
(End) T. Pribulla [Astron. Institute, SAS], P. Vannier [CDS] 17-Jan-2011
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