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 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
yymmddnn.fit, where "yymmdd" gives the evening date and "nn" is number
of the spectrum within that night.
Objects:
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RA (2000) DE Designation(s)
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08 44 42.2 -54 42 32 HD 74956 = V* del Vel
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 40 63 Journal of spectroscopic observations at
Cerro Armazones Observatory
sp/* . 63 FITS files of spectra
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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
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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.
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Acknowledgements:
Theodor Pribulla, Astron. Institute, Slovak Academy of Sciences,
pribulla(at)ta3.sk
(End) T. Pribulla [Astron. Institute, SAS], P. Vannier [CDS] 17-Jan-2011