Mon. Not. R. Astron. Soc., 432, L26-L30 (2013/June-2)
R144 revealed as a double-lined spectroscopic binary.
SANA H., VAN BOECKEL T., TRAMPER F., ELLERBROEK L.E., DE KOTER A., KAPER L., MOFFAT A.F.J., SCHNURR O., SCHNEIDER F.R.N. and GIES D.R.
Abstract (from CDS):
R144 is a WN6h star in the 30 Doradus region. It is suspected to be a binary because of its high luminosity and its strong X-ray flux, but no periodicity could be established so far. Here, we present new X-shooter multi-epoch spectroscopy of R144 obtained at the ESO Very Large Telescope. We detect variability in position and/or shape of all the spectral lines. We measure radial velocity variations with an amplitude larger than 250 km s-1 in N iv and N v lines. Furthermore, the N iii and N v line Doppler shifts are anticorrelated and the N iv lines show a double-peaked profile on six of our seven epochs. We thus conclude that R144 is a double-lined spectroscopic binary. Possible orbital periods range from two to six months, although a period up to one year is allowed if the orbit is highly eccentric. We estimate the spectral types of the components to be WN5-6h and WN6-7h, respectively. The high luminosity of the system (logLbol/L☉ ~ 6.8) suggests a present-day total mass content in the range of about 200-300 M☉, depending on the evolutionary stage of the components. This makes R144 the most massive binary identified so far, with a total mass content at birth possibly as large as 400 M☉. We briefly discuss the presence of such a massive object, 60 pc away from the R136 cluster core in the context of star formation and stellar dynamics.
© 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2013)
binaries: spectroscopic - stars: early-type - stars: formation - stars: individual: RMC 144 - stars: Wolf-Rayet
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