arXiv:1108.4453v1 [astro-ph.SR] 22 Aug 2011 a iso rmwr rga ee ne h ai ui Inter Curie Marie the under Seven PIRG04-GA-2008-239335. Program Framework mission n xrce sn IRAF using The Chile. extracted Observatory, Campanas and Las at telescope Magellan meter tr,()tedtriaino yaia oe ii o h aso mass . indepe absolute the an expected for for the opportunity limit on great lower based a distance, dynamical present the t EBs a and (4) of formation and the determination progenitor for the models wit (3) stellar of stars, massive of test sample the small (2) the increase parameters, t to of im order parameters is in fundamental cluster etc.), the radii, of in determination systems the these (1) of study reasons: the Thus, stars. of radii 20)i -as hsmgea saso -a usrta sassume is that X-ray . slow progenitor a massive is a c from the This Bonanos in X-rays. discovered see in was WR77o, (2006) J164710.2-455216 CXO Wd36, as magnetar Wd13, supergiants, the (Wddeb, more, OB systems many yello variable, blue, binary as blue eclipsing such luminous stars, a d high-mass its stars, (1 evolved Wolf-Rayet in Westerlund rare extinction by interstellar of discovered high assortment was the an It to Myr. due recently 3-5 until of unstudied age an with galaxies, o eerhi srnm,Ic,udrcoeaieagreeme cooperative under Inc., Astronomy, in Research for ..Eio,BD dtr&CE dtr eds. Editor, C.E. & Editor B.D. 2011 Editor, 282, A.C. No. Symposium IAU Proceedings Tools Modelling Exoplanets: Essential to Binaries Interacting From aees tr:erytp,bnre:elpig stars: eclipsing, binaries: early-type, stars: rameters, o ihms o h rgntro h magnetar. the of progenitor Keywords. the for res mass Our high cluster. the a to for distance lowe independent dynamical an a masses obtain determine to to accurate and used measure be evolution further for to can constraints parameters is needed much goal provide which The stars, 1. Westerlund cluster Abstract. χ ‡ † ehv nlzdsetao l cisn iais ae n2007-20 in taken binaries, eclipsing 4 all of spectra analyzed have We binaries individual The 2. cisn iaispoieteol cuaewyfrtemeasuremen the for way accurate only the provide binaries Eclipsing etrud1i n ftems asv on lseskoni h L the in known clusters young massive most the of one is 1 Westerlund Introduction 1. epeetfnaetlprmtr f4msieelpigbi eclipsing massive 4 of parameters fundamental present We 2 RFi itiue yteNA,wihaeoeae yteAss the by operated are which NOAO, the by distributed is IRAF K&ABakoldersac n rvlspotfo h IAU the from support travel and research acknowledge AZB & EK iiiaintcnqe hc nsteleast the finds which technique, minimization udmna aaeeso Massive 4 of Parameters Fundamental cisn iaisi etrud1 Westerlund in Binaries Eclipsing ainlOsraoyo tes nttt fAtooy&As & Astronomy of Institute Athens, of Observatory National .Mtx a.Pvo t,Pli etl R126Athens, GR-15236 Penteli Palaia St., Pavlou Vas. & Metaxa I. pncutr n soitos niiul(etrud1) (Westerlund individual associations: and clusters open [email protected] .KupaadAZ Bonanos A.Z. and Koumpia E. ‡ o h eemnto fterda eoiisw adopted we velocities radial the of determination the For . , 1 [email protected] Wolf-Rayet χ

c 2 r oeso asv tr.Accurate stars. massive of models ary 01ItrainlAtooia Union Astronomical International 2011 lscnr n xedteevidence the extend and confirm ults rmteosre pcrmand spectrum observed the from twt h NSF. the with nt ii o h antrprogenitor magnetar the for limit r O:00.0000/X000000000000000X DOI: n ai ftercomponent their of radii and ainlRitgainGrant Reintegration national aisi h on massive young the in naries ecmoetsas(mass, stars component he † otn o h following the for portant eeouino massive of evolution he n e supergiants, red and w tr:fnaetlpa- fundamental stars: , dn esrmn of measurement ndent n h uoenCom- European the and caino Universities of ociation elkonphysical known well h utrb uoe al. et Muno by luster pcr eereduced were spectra trophysics, rcin tcontains It irection. 6) u remained but 961), Greece ela massive 4 as well ohv formed have to d fmse and masses of t 07.Further- 2007). h magnetar the f 8wt h 6.5 the with 08 clGopof Group ocal 2 Koumpia & Bonanos fixed synthetic TLUSTY models (Lanz & Hubeny 2003). For this purpose we used the narrow Helium lines (λλ6678, 7065), as they are less sensitive to systematics, rather than the broader hydrogen lines. The physical and orbital parameters of the members of the 4 systems (period, masses, radii, surface gravities of the components, eccentricity, inclination etc.), resulted from modelling light and curves using PHOEBE software (Prsa & Zwitter 2005). Our final results will be presented in Koumpia & Bonanos (in prep.). Wd13: is a semi-detached, double-lined spectroscopic binary (B0.5Ia+/WNVL and O9.5-B0.5I types, Ritchie et al. 2010) in a circular orbit (see Fig. 1). Its spectra show both absorption and emission lines. It provides the first dynamical constraint on the mass of the magnetar progenitor and has important implications for the threshold mass which gives rise to black holes versus neutron stars. Wd36: is an overcontact, double-lined spectroscopic binary system (OB-type) in a cir- cular orbit. WR77o: is probably a double contact binary system in an almost circular orbit. It is a single lined spectroscopic binary. The spectroscopic visible star is a Wolf-Rayet star of spectral type WN6-7 (Negueruela & Clark 2005), with line widths of 2000 km s−1. Wddeb: is a double-lined spectroscopic binary system (OB-type) with an eccentricity of almost 0.2. Being a detached system, it contains the first main-sequence stars detected in the cluster, yielding masses of 2 of the most massive unevolved stars in Wd1. 3. Conclusions Having obtained the physical and orbital parameters of each system, we confirm the high mass of Wd13 and therefore the high mass of the magnetar progenitor, also found by the independent study of Ritchie et al. (2010). We also compared our results with stellar models of evolution of single stars (Claret 2004).

Figure 1: Phased R light curve and radial velocity curve of Wd13, respectively. Radial velocity points from Ritchie et al. (2010) are also included (black squares). References Bonanos, A.Z. 2007, AJ, 133, 2696 Claret, A. 2004, A&A, 428, 1001 Lanz, T. & Hubeny, I. 2003, ApJS, 146, 417 Muno, M. P., Clark, J. S., Crowther, P. A. et al. 2006, ApJ, 636, 41 Negueruela, I. & Clark, J. S. 2005, A&A, 436, 541 Negueruela, I., Clark, J. S. & Ritchie, B. W. 2010, A&A, 516, 78 Prsa, A. & Zwitter, T. 2005, ApJ, 628, 426 Westerlund, B. 1961, AJ, 66, 57