J/MNRAS/455/1275 Radial velocities of WR21a (Tramper+, 2016)
The mass of the very massive binary WR21a.
Tramper F., Sana H., Fitzsimons N.E., de Koter A., Kaper L., Mahy L.,
Moffat A.
<Mon. Not. R. Astron. Soc. 455, 1275 (2016)>
=2016MNRAS.455.1275T 2016MNRAS.455.1275T (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, spectroscopic ; Stars, Wolf-Rayet ; Radial velocities
Keywords: binaries: close - binaries: spectroscopic - stars: early-type -
stars: fundamental parameters - stars: individual: WR21a -
stars: Wolf-Rayet
Abstract:
We present multi-epoch spectroscopic observations of the massive
binary system WR21a, which include the 2011 January periastron
passage. Our spectra reveal multiple SB2 lines and facilitate an
accurate determination of the orbit and the spectral types of the
components. We obtain minimum masses of 64.4±4.8M_☉ and
36.3±1.7M_☉ for the two components of WR21a. Using disentangled
spectra of the individual components, we derive spectral types of
O3/WN5ha and O3Vz ((f*)) for the primary and secondary, respectively.
Using the spectral type of the secondary as an indication for its
mass, we estimate an orbital inclination of i=58.8±2.5° and
absolute masses of 103.6±10.2M_☉ and 58.3±3.7M☉, in
agreement with the luminosity of the system. The spectral types of the
WR21a components indicate that the stars are very young (1-2Myr),
similar to the age of the nearby Westerlund 2 cluster. We use
evolutionary tracks to determine the mass-luminosity relation for
the total system mass. We find that for a distance of 8kpc and an age
of 1.5Myr, the derived absolute masses are in good agreement with
those from evolutionary predictions.
Description:
All observations of WR21a have been obtained with the X-Shooter
spectrograph mounted on the European Southern Observatory's VLT. The
observational campaign has been designed to intensively cover the 2011
January periastron passage, as well as to provide coverage of the
orbit on longer time-scales.
Objects:
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RA (2000) DE Designation(s)
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10 25 56.50 -57 48 43.5 WR21a = AX J1025.9-5749
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 52 26 Observational log and RV measurements
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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- 2 I2 --- Epoch Epoch of observation
4- 12 F9.4 d HJD Heliocentric Julian date at mid-exposure
(HJD-2450000)
14 I1 --- Nexp Number of 90s exposures
16- 19 F4.2 --- Airmass Average airmass during observation
21- 22 I2 --- SNR Signal-to-noise ratio per wavelength
bin of 0.2 nm
24- 28 F5.3 --- Phase Orbital phase
30- 35 F6.1 km/s RVwr Radial velocity (RV) of the WR-star component
37- 40 F4.1 km/s e_RVwr 1 sigma error on the RV of the WR-star component
42- 47 F6.1 km/s RVo RV of the O-star component
49- 52 F4.1 km/s e_RVo 1 sigma error on the RV of the O-star component
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Acknowledgements:
Frank Tramper, F.Tramper(at)uva.nl
(End) Frank Tramper [UvA, Netherlands], Patricia Vannier [CDS] 09-Feb-2015