J/ApJ/908/L3 Radial velocity in a Wolf-Rayet/O-star couple (Richardson+, 2021)
The First Dynamical Mass Determination of a Nitrogen-rich Wolf-Rayet Star Using
a Combined Visual and Spectroscopic Orbit.
Richardson N.D., Lee L., Schaefer G., Shenar T., Sander A.A.C., Hill G.M.,
Fullard A.G., Monnier J.D., Anugu N., Davies C.L., Gardner T.,
Lanthermann C., Kraus S., Setterholm B.R.
<Astrophys. J., 908, L3 (2021)>
=2021ApJ...908L...3R 2021ApJ...908L...3R
ADC_Keywords: Stars, double and multiple; Stars, O; Stars, Wolf-Rayet;
Spectra, optical; Radial velocities
Keywords: Interferometric binary stars ; Wolf-Rayet stars ; Spectroscopic
binary stars ; WN stars ; O supergiant stars ; Massive stars
; Stellar masses
Abstract:
We present the first visual orbit for the nitrogen-rich Wolf-Rayet
binary, WR133 (WN5o+O9I), based on observations made with the CHARA
Array and the MIRC-X combiner. This orbit represents the first visual
orbit for a WN star and only the third Wolf-Rayet star with a visual
orbit. The orbit has a period of 112.8days, a moderate eccentricity of
0.36, and a separation of a=0.79 mas on the sky. We combine the visual
orbit with an SB2 orbit and Gaia parallax to find that the derived
masses of the component stars are MWR=9.3±1.6M☉ and
MO=22.6±3.2M☉, with the large errors owing to the nearly
face-on geometry of the system combined with errors in the
spectroscopic parameters. We also derive an orbital parallax that is
identical to the Gaia-determined distance. We present a preliminary
spectral analysis and atmosphere models of the component stars, and
find the mass-loss rate in agreement with polarization variability and
our orbit. However, the derived masses are low compared to the
spectral types and spectral model. Given the close binary nature, we
suspect that WR133 should have formed through binary interactions,
and represents an ideal target for testing evolutionary models given
its membership in the cluster NGC6871.
Description:
The observations were taken with the Dominion Astrophysical
Observatory 1.83m telescope (DAO), and had a resolution element of
1.33Å. In addition, we collected 34 more observations with the same
telescope and spectrograph configuration, so that our total data set
spans the years 1986-2013. The observations cover the wavelength range
of 5150-6000Å, allowing for measurement of the HeII λ5411
emission feature for the WR star, and the absorption features of HeII
λ5411, HeI λ5876, and OIII 5592 from the O star.
Objects:
-----------------------------------------------
RA (ICRS) DE Designation(s)
-----------------------------------------------
20 06 11.52 +35 45 53.9 NGC6871 = C 2004+356
20 05 57.32 +35 47 18.1 WR 133 = ** BU 440A
-----------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig2.dat 35 60 The spectroscopic orbits of the two component stars
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See also:
B/polarbase : PolarBase spectropolarimetric database (Petit+, 2014)
J/A+A/438/1163 : Catalogue of Open Cluster Data (COCD) (Kharchenko+, 2005)
J/AJ/137/3358 : Speckle interferometry of massive stars (Mason+, 2009)
J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)
J/PASP/126/469 : PolarBase catalogue of stellar spectra (Petit+, 2014)
J/ApJS/215/15 : SMaSH+; observations and companion detection (Sana+, 2014)
J/A+A/562/A135 : Northern Galactic OB stars vsini (Simon-Diaz+, 2014)
J/AJ/149/26 : Massive binary stars from HST/FGS survey (Aldoretta+, 2015)
J/A+A/579/A68 : CANDID code interferometric observations (Gallenne+, 2015)
J/AJ/152/213 : Interfer & spectroscopy of sigma Orionis (Schaefer+, 2016)
J/A+A/625/A104 : Stellar param of OB stars in SMC wing (Ramachandran+, 2019)
J/AJ/159/214 : UBVRI linear polarisation Wolf-Rayet winds (Fullard+, 2020)
J/MNRAS/493/1512 : Galactic Wolf-Rayet stars with Gaia DR2 I (Rate+, 2020)
Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 13 F13.4 d HJD [46658/58295] Heliocentric Juliand Date;
HJD-2400000
15- 19 F5.1 km/s RVelWR [25.2/144] Radial Velocity of the Wolf-Rayet
star
21- 24 F4.1 km/s e_RVelWR [3/49] Error in RVelWR
26- 30 F5.1 km/s RVelO [-42.3/2.6] Radial Velocity of the O star
32- 35 F4.1 km/s e_RVelO [1/19] Error in RVelO
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 26-Feb-2024