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TOPIC: HDE 269928

Blobrana

L

Posts: 131433

Date: May 18 21:41 2013

R144	Permalink

Title: R144 revealed as a double-lined spectroscopic binary Authors: H. Sana, T. van Boeckel, F. Tramper, L.E. Ellerbroek, A. de Koter, L. Kaper, A.F.J. Moffat, O. Schnurr, F.R.N. Schneider, D.R. Gies 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 Xshooter multi-epoch spectroscopy of R144 obtained at the ESO Very Large Telescope (VLT). 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 in NIV and NV lines. Furthermore, the NIII and NV line Doppler shifts are anti-correlated and the NIV 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 2 to 6 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 (log Lbol/Lsun ~ 6.8) suggests a present-day total mass content in the range of about 200 to 300 solar masses, 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 solar masses. 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. Read more (213kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Jan 7 16:34 2009

HDE 269928	Permalink

Title: A first orbital solution for the very massive 30 Dor main-sequence WN6h+O binary R145 Authors: O. Schnurr, A.F.J. Moffat, A. Villar-Sbaffi, N. St-Louis, N.I. Morrell We report the results of a spectroscopic and polarimetric study of the massive, hydrogen-rich WN6h stars R144 (HD 38282 = BAT99-118 = Brey 89) and R145 (HDE 269928 = BAT99-119 = Brey 90) in the LMC. Both stars have been suspected to be binaries by previous studies (R144: Schnurr et al. 2008b; R145: Moffat 1989). We have combined radial-velocity (RV) data from these two studies with previously unpublished polarimetric data. For R145, we were able to establish, for the first time, an orbital period of 158.8 days, along with the full set of orbital parameters, including the inclination angle i, which was found to be i = 38 ± 9 deg. By applying a modified version of the shift-and-add method developed by Demers et al. (2002), we were able to isolate the spectral signature of the very faint-line companion star. With the RV amplitudes of both components in R145, we were thus able to estimate their absolute masses. We find minimum masses M_WR sin³i = (116 ± 33) Solar masses and M_O sin³i = (48 ± 20) Solar masses for the WR and the O component, respectively. Thus, if the low inclination angle were correct, resulting absolute masses of the components would be at least 300 and 125 Solar masses, respectively. However, such high masses are not supported by brightness considerations when R145 is compared to systems with known, very high masses such as NGC3603-A1 or WR20a. An inclination angle close to 90 degrees would remedy the situation, but is excluded by the currently available data. More and better data are thus required to firmly establish the nature of this puzzling, yet potentially very massive and important system. As to R144, however, the combined data sets are not sufficient to find any periodicity. Read more (166kb, PDF) __________________

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