Astron. Astrophys. 320, 500–524 (1997) ASTRONOMY AND ASTROPHYSICS

Fundamental parameters of Wolf-Rayet stars VI. Large Magellanic Cloud WNL stars?

P.A.Crowther and L.J. Smith Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK

Received 5 February 1996 / Accepted 26 June 1996

Abstract. We present a detailed, quantitative study of late WN Key words: stars: Wolf-Rayet;mass-loss; evolution; fundamen- (WNL) stars in the LMC, based on new optical spectroscopy tal parameters – galaxies: Magellanic Clouds (AAT, MSO) and the Hillier (1990) atmospheric model. In a pre- vious paper (Crowther et al. 1995a), we showed that 4 out of the 10 known LMC Ofpe/WN9 stars should be re-classified WN9– 10. We now present observations of the remaining stars (except the LBV R127), and show that they are also WNL (WN9–11) 1. Introduction stars, with the exception of R99. Our total sample consists of 17 stars, and represents all but one of the single LMC WN6– Quantitative studies of hot luminous stars in galaxies are im- 11 population and allows a direct comparison with the stellar portant for a number of reasons. First, and probably foremost, parameters and chemical abundances of Galactic WNL stars is the information they provide on the effect of the environment (Crowther et al. 1995b; Hamann et al. 1995a). Previously un- on such fundamental properties as the mass-loss rate and stellar published ultraviolet (HST-FOS, IUE-HIRES) spectroscopy are evolution. In the standard picture (e.g. Maeder & Meynet 1987) presented for a subset of our programme stars. mass-loss significantly affects the evolution of massive O stars We find observational evidence for lower metallicities in as they proceed through an Of phase, then an unstable Luminous LMC WNL stars compared to the Galaxy, though this is not re- Blue Variable (LBV) phase, before becoming late WN (WNL) flected in their stellar properties. For Galactic and LMC stars we stars. The current theory of driving mass-loss through radiation find: (i) a similar range in temperature and luminosity, in contrast pressure predicts mass-loss to scale as the square-root of the metallicity (Kudritzki et al. 1989). The evolution of massive to evolutionary. predictions; (ii) comparable wind performance values (Mv∞/[L/c]) and hydrogen composition, with a broad stars should therefore be strongly dependent on the local envi- correlation between increasing helium content and wind perfor- ronment (Maeder 1991; Maeder & Meynet 1994). Thus stud- mance number; (iii) a general trend to lower wind velocities at ies of massive stars at different metallicities should enable a lower stellar temperature, with possibly slower winds for LMC direct comparison of observations with evolutionary and radia- WN9–11 stars. Some 30 Dor WNL stars show exceptional prop- tion driven wind theory. The question of exactly how mass-loss erties: Brey 89 (HD 38282, WN6h) has the highest luminos- scales with metallicity is of enormous importance. For exam- . −1 ity (log (L/L )∼6.25) and mass-loss rate (log (M/(M yr )) ple, it affects the early chemical enrichment of galaxies, and ∼−3.6) known for any WR star, while Brey 80 (R135, WN7h) the evolution of starbursts containing many thousands of O and has an enormous wind performance number of 50. The observed Wolf-Rayet (WR) stars (e.g. Leitherer & Heckman 1995). physical properties of our sample of LMC WNL stars supports In this series of papers we have studied the physical and the Crowther et al. (1995c) evolutionary scheme for Galactic chemical nature of predominantly Galactic Wolf-Rayet stars by stars, in that the most massive O stars, exclusive to 30 Dor, combining detailed model atmosphere calculations with high evolve directly to O3 If/WN6 and subsequently WN6–7 stars quality, multi-wavelength observations. In particular, we have (e.g. Brey 89), without passing through an intermediate LBV investigated WNL stars (Crowther et al. 1995a,b,c, hereafter phase. In contrast, lower initial mass stars evolve through a Papers I–III), weak-lined, early WN (WNE) stars (Crowther et LBV phase, encompassing a WN9–11 stage (e.g. BE294), with al. 1995d) and intermediate WN/C stars (Crowther et al. 1995e). WN8 stars being their immediate successors. Other related studies have been conducted on LBVs (L.J. Smith et al. 1994), Of stars (Crowther & Bohannan 1997), an M33 Send offprint requests to: P.A.Crowther ([email protected]) WR star (L.J. Smith et al. 1995), and strong-lined WNE stars ? Based on observations collected at the Anglo-Australian and Mount in the infrared (Crowther & Smith 1996). WC and WNE stars Stromlo Observatories, Australia have not been widely investigated to date since we anticipate P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 501 that their parameters will be the most susceptible to the effects Table 1. A complete list of LMC WN6–8 and Ofpe/WN9 stars (exclud- of line blanketing, given their dense winds and high excitation. ing O3 If/WN6 stars). We preferentially use Breysacher (1981, Brey), In this, the final paper of the current series, we present a study Henize (1956, S) and Bohannan & Epps (1974, BE) catalogue numbers, of WNL stars in the Large Magellanic Cloud (LMC). These stars as indicated with an underline. Other catalogue references are Feast et have the distinct advantage over their Galactic counterparts in al. (1960, R), Westerlund & Smith (1964, WS), Sanduleak (1969, Sk), that they lie at a known distance and suffer only moderate in- Fehrenbach et al. (1976, FD), Azzopardi & Breysacher (1985, AB) terstellar extinction. It is thus much easier to determine reliable and Melnick (1985, Mk). WR spectral classifications are taken from absolute fluxes and mass-loss rates. A direct comparison with L.F. Smith et al. (1996), Melnick (1985) and herein Galactic WNL stars (Papers I–III) will allow us to investigate any differences in fundamental properties and evolution, as a result of the lower metallicity of the LMC, by a factor of 2– Brey HD(E) WS FD BE S R Sk/other Sp Type Note 3 (Spite & Spite 1991). The first quantitative comparison of 10b 9 −66◦40 WN10h ◦ the properties of LMC and Galactic WR stars was performed 13 33133 8 12 14 −66◦51 WN8h • by L.J. Smith & Willis (1983) who found no differences ex- 18 269227 12 17 543 91 84 −69◦79 WN9h ◦ cept that the LMC WN stars had stronger He ii emission lines. 24 18 23 28 −65◦55 WN6h • More recently, Koesterke et al. (1991) suggested that, while the 269445 261 30 99 −68◦73 Of/WN∗ • LMC WN stars showed no clear differences from their Galactic 26 36063 19 24 569 161 −71◦21 WN6(h)+? •† counterparts in mass-loss rates or wind velocities, they do have 36 27 32 280 108 −69◦141 WN8h • ◦ ∗ lower stellar luminosities. Nevertheless, it is well known that 269582 294 −69 142a Of/WN • 44a AB18 WN8–9∗ • our Galaxy and the LMC exhibit quite different WN:WC ratios; ◦ ∗ in the solar neighbourhood this ratio is 1:1 and in the LMC it is 269687 335 119 −69 175 Of/WN • 47 42 −68◦115 WN6h • 5:1. It has been suggested that this difference may be directly 57 53 WN7h+? (4) † attributed to metallicity effects (e.g. L.F. Smith 1991). It is also 58 AB4 WN5–6 (1) interesting to note that the frequency distribution of WN stars 64 381 WN9h ◦ among the subtypes is different between the two galaxies; in 65 269828 38 55 383 −69◦209a WN7+.. (2) † the Galaxy there is a broad peak between WN5–6 whereas the 269858f 397 128 127 −69◦220 Of/WN LMC shows a sharp peak at WN4 (L.F. Smith et al. 1996). 71 269883 60 −69◦233 WN7h • Our previous Galactic studies (Papers I–III; Crowther & Bo- 73 AB10 WN7+OB? (2) † hannan 1997) have led to the discovery of different evolutionary 75 63 134 WN6(h) • routes for the formation of WNL stars. In particular, we find 76a Mk37Wa WN7? (3) † 79 Mk49 WN6(h)+? (4) † that very massive early Of stars (≥ 60 M ) evolve to WN6–7 stars with an Ofpe or WNL+abs (hereafter WNLha following 80 64 135 WN7h • 81 Mk53 WN8(h)+? •† L.F. Smith et al. 1996) intermediate stage. For less massive pro- ◦ 82c 38268c 66 609 136c −69 241c WN7o?+OB (3) † genitors, evolution instead proceeds through an intermediate 89 38282 46 70 420 133 144 −69◦246 WN6h • LBV stage to the WN8 spectral type, with WN9–11 stars rep- 90 269928 47 71 421 145 −69◦248 WN6(h)+? •† resenting either dormant or post-LBVs. This evolutionary sce- 91 269927c −69◦249c WN9h ◦ nario naturally explains the observed dichotomy among WNL 470 142 −69◦297 Of/WN∗ • stars (Moffat 1989). However, this scenario is based principally 153 61 −67◦266 Of/WN∗ • on studies of Galactic objects, and it is therefore of interest to examine if it is viable in lower metallicity environments such •: programme star as the LMC. ◦: star previously studied in Paper I 00 In Sects. 2–3 we present and discuss new ultraviolet and op- †: object considered to be multiple at a spatial resolution ≥1 tical observations of a substantial sample of LMC WNL stars. ∗: programme Of/WN stars and AB18 are re-classified in Sect. 3 The fundamental parameters of our sample are derived and dis- References: (1) Breysacher (1981); (2) Walborn et al. (1995b); (3) Parker (1993); (4) see text cussed in Sect. 4. Finally in Sect. 5, we compare the results of this analysis with our Galactic sample and discuss the implica- tions of our results for radiatively-driven winds and evolutionary theories of massive stars. et al. (1996) which classifies WN stars on the basis of their he- lium line strengths and widths, and the presence of hydrogen 2. Observations (denoted by ‘h’). Our primary source of LMC WN stars is the catalogue of Breysacher (1981, 1986). Since we can only reli- We have sought to obtain observations of every bona-fide late ably derive parameters for single stars, we have excluded those WN star in the LMC. For the purposes of this paper, we de- stars which are believed to be multiple (Brey 82 (R136), Brey 65 fine a WNL star as being of spectral type WN6 or later and (HDE 269828), Brey 73 (AB10) and Brey 76a (Mk37Wa)). Our containing hydrogen. Throughout this paper, we have adopted own unpublished spectra suggest that Brey 57 (WN7h) and the new three-dimensional classification scheme of L.F. Smith Brey 79 (WN6(h)) suffer significant contamination from un- 502 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI known companions, and these stars have also been excluded. The Mount Stromlo observations were taken with the coude´ From our sample, Brey 26 and Brey 90 show radial velocity spectrograph, 32 in. camera and Tektronix CCD (2048×2048, variability (Moffat 1989), suggestive of unseen companions, 24µm pixels). We used the 300 and 600 l mm−1 gratings, both while Parker (1993) found Brey 81 to be multiple, although its blazed at 5000A,˚ resulting in dispersions of 0.96A˚ pixel−1 and companion is also not seen spectroscopically. Some stars in the 0.49A˚ pixel−1 and spectral resolutions of 2.0A˚ and 1.0A,˚ re- Breysacher catalogue have been recently re-classified to earlier spectively, as measured from the widths of Cu-Ar arc lines. WN spectral types (Brey 56 to WN5h?+OB; Brey 92 to WN4– This dataset extended our wavelength coverage further into the 6h?pec; L.F. Smith et al. 1996) or to Of spectral type (Brey 86 red for our brightest objects, enabled higher spectral resolu- to O6 Iaf) and thus these have also been omitted. We provide tion observations of He i λ5876 and Hα for programme Of/WN what we consider to be the complete list of LMC WNL stars in stars, and allowed observations of two previously unobserved Table 1, and give their various catalogue names. From a known stars (Brey 75, 81) to be made (see Table 4). These data were LMC population of 19 WN6–8 stars (including AB18), we are reduced in an identical manner to our AAT–RGO observations. left with 13 single stars suitable for a quantitative analysis, of Further AAT high resolution observations of S119 and R99 which we have observed 12 stars – only Brey 58 (WN5–6?) is were collected with the UCL echelle spectrograph (UCLES), missing. Following the recent literature, we preferentially utilise 31.6 lines mm−1 grating, and blue Thomson CCD (1024 × Breysacher (1981) catalogue names and spectral classifications 1024, 19µm pixels). A slit width of 100 yielded a spectral res- from L.F. Smith et al. (1996), Melnick (1985) or Breysacher olution in the extracted spectra of ∼0.10 A,˚ as measured from (1981, 1986). the widths of Th-Ar arc lines. Two overlapping settings were re- In Paper I we presented arguments for the re-classification quired for complete spectral coverage between λλ4070–5100. of spectrally composite Ofpe/WN9 stars to Wolf-Rayet stars, The CCD frames were first bias-subtracted, and the echelle at least for some members of this class. We have therefore in- orders were optimally extracted using the software package cluded in Table 1 the ten known LMC Ofpe/WN9 stars from echomop (Mills & Webb 1994). Subsequent analysis was Bohannan & Walborn (1989). We have observed the remain- again performed using the dipso package. ing five Ofpe/WN9 stars (excluding the LBV R127, Stahl et In addition to the new observations detailed above, we have al. 1983) from Paper I to verify their spectroscopic and evolu- made use of the atlas of low resolution flux calibrated WR spec- tionary status. Since no standard nomenclature exists for each tra of Torres-Dodgen & Massey (1988), of which eight are com- star, we follow the recent tradition of using Henize (1956) and mon to the programme stars. Bohannan & Epps (1974) catalogue numbers, in preference to the Feast et al. (1960), Sanduleak (1969) and HD catalogues 2.2. Ultraviolet observations (except for R99). Finally, for completeness, we note that we have omitted from this study the O3 If/WN6 stars introduced We have obtained short wavelength (SWP) high resolution by Walborn (1986) which show a normal O3 If spectrum plus (HIRES) IUE observations of Brey 13, 24, and 26 at the ESA relatively broad, strong He ii λ4686 emission. tracking station at Vilspa, Madrid during 1992–1993 (see Ap- pendix: Table 5) while archive observations of two further pro- gramme stars (Brey 89, and 90) were obtained from the World 2.1. Optical observations Data Centre at the Rutherford Appleton Laboratory and reduced iuedr We have obtained new optical spectra of our seventeen pro- using (Giddings et al. 1995). gramme LMC stars at the 3.9m Anglo-Australian Telescope All programme stars have previously been observed by IUE (AAT) between 1991 December–1994 December and at the at low resolution (LORES) between 1978–1993, with the excep- 1.9m telescope at the Mount Stromlo Observatory (MSO) in tion of AB18, Brey 75 and Brey 81. These observations were 1995 December. The journal of observations is given in the Ap- generally accessed via the Uniform Low-Dispersion Archive pendix (Table 4). (ULDA; Talavera 1988) and provided useful interstellar red- AAT optical observations were principally obtained with dening constraints. Hubble Space Telescope (HST) the RGO spectrograph, 25cm camera, Tektronix CCD (1024 We have also obtained Faint Object Spectrograph (FOS) observations of R99, BE294, × 1024, 24µm pixels), 1200V grating (1200B also for 1992 HST November) and a slit width of 200. The measured spectral reso- S119, and S61 from the data archive (see Appendix: − ◦ lution in the extracted spectra is 1.6–1.8A,˚ using the FWHMs of Table 5), additionally including the WN9h star Sk 69 249c the Cu-Ar arc spectra taken either before or after every stellar (=HDE 269927c) from Paper I These observations were carried exposure. Each object was observed at three spectrally over- out in 1993 by Dr C. Leitherer (see Table 5) using both the lapping settings covering in total 3670–6005A.˚ The CCD data G130H (λλ1153–1606), and G190H (λλ1573–2330) gratings. were bias-corrected, flat-fielded and then optimally extracted using the pamela (Horne 1986) routines within figaro (Mey- 3. Stellar spectra erdierks 1993). Photometric standards were observed each night 3.1. Optical classification to flux calibrate the stellar spectra. Once calibrated, the spectra were rectified using low order polynomials and measured within For spectral classifications of WN6–8 stars we follow the recent dipso (Howarth et al. 1995). L.F. Smith et al. (1996) scheme in preference to earlier classifi- P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 503

Fig.1.aA comparison of the emission equivalent widths (Wλ)ofHeiλ5876 ver- sus He ii λ4686 for Ofpe, WN6–11 stars in the Galaxy (open symbols) and LMC (filled-in symbols), with symbols defined below, in (b), except for the peculiar ob- ject R99 which is indicated by an aster- isk (see Sect. 3.6). Approximate bound- aries of spectral classes are shown as dot- ted lines, while Of (e.g. HD151804) and B supergiants (e.g. HDE 316285) lie off our scale, as indicated while for clarity not ev- ery Galactic object is labelled; b Compari- son of He ii λ4686 equivalent width (Wλ) with FWHM. While there is a strong corre- lation of FWHM versus Wλ for both WNL and Of stars, this relation is not a useful discriminant for individual sequences 504 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI cations since (i) the overall scheme based primarily on He i-ii little atmospheric hydrogen (H/He ≤0.10; Paper II), suggests line strengths is more quantitative and objective. For instance that (at least some) WN8 stars must be helium burning. it avoids the metallicity effect of using the N iii λλ4634–41 to Although our initial classification scheme for WN9–11 stars He ii λ4686 ratio as a criterion for WN8 subtypes; (ii) it is based was limited to the relative strengths of N ii-iv emission lines on modern CCD observations, including our own; and (iii) it in- (L.J. Smith et al. 1994), we have since discovered that use of cludes additional properties such as the presence or absence of He i-ii emission line strengths provides a fully consistent clas- hydrogen. Relative to previous schemes (e.g. Breysacher 1981) sification criterion (L.J. Smith et al. 1995). The advantage of the several stars are re-classified to WN6 from WN7 while Brey 47, latter is that for lower quality data and weaker-lined objects, rel- previously mis-classified as WN8 is now given a WN6 classifi- ative helium equivalent widths are more readily obtained than cation (L.F. Smith et al. 1996). those of nitrogen, and this forms a natural extension to the WN Turning to the Ofpe/WN9 stars (and AB18), we have pre- classification scheme of L.F. Smith et al. (1996). In Fig. 1a we viously argued that four such stars should be re-classified as present comparisons of measured emission equivalent widths WN9 or WN10 stars, based on the relative strengths of their ni- for He i λ5876 versus He ii λ4686 for our LMC programme trogen lines (Paper I). Similarly, the spectral classification of the stars. We also show values for the Galactic WN6–11 counter- Galactic LBV candidate He 3–519 was revised from Ofpe/WN9 parts, preferentially taken from Paper III and L.J. Smith et al. to WN11 by L.J. Smith et al. (1994). The purpose of this re- (1994), or our own measurements from Hamann et al. (1995b), classification is as follows: LMC WN9–10 stars from Paper I, and several Of stars includ- ing the prototype LMC O3 If/WN6 star Sk−67◦22. Using the 1. These objects form a natural, smooth extension to the WN relative strengths of the N ii–N iv emission lines as the primary morphological sequence at lower excitation, using the Wolf- classification criterion (Paper I), we are able to draw approxi- Rayet classification criteria from Conti (1973). mate boundaries to the spectral classes as shown in Fig. 1a, and 2. The surface chemistries of the WN9–11 stars are quantita- then use this diagram for classification purposes. We note that tively indistinguishable from stars of earlier WN spectral the boundary lines are not vertical because while the strength of type and so should also be included in the WR population He ii is primarily an excitation diagnostic, the strength of He i when comparing, e.g. theoretically predicted WR:O life- λ5876 also strongly depends on wind density. It is thus pos- times with observation. sible to have WN6 and WN8 stars with the same He ii λ4686 3. The (unintentional) implication that Ofpe/WN9 stars repre- line strength but vastly different He i λ5876 line strengths. In sent objects at a phase in their evolution directly between Fig. 1b we present He ii λ4686 equivalent width versus FWHM Ofpe and WN9 is misleading. For example, BE381 (pre- measurements for Galactic and LMC WNL and Of stars. While viously Ofpe/WN9) is apparently progressing between a WNL stars within both galaxies obey a tight relation between LBV and a classical WN8 phase (Paper I). Similarly, He 3– He ii λ4686 line strength and width (Bohannan 1990), this line 519 (WN11, previously Ofpe/WN9) is probably a dormant alone is not a useful discriminator between WN9–11 and Of LBV, showing a visual excitation more representative of a stars (L.J. Smith et al. 1995; Crowther & Bohannan 1997) al- B supergiant than a late Of star (L.J. Smith et al. 1994). In though it is useful for identifying candidate WNL binaries. contrast, HD 152408 (O8 :Iafpe) appears to be advancing From Fig. 1a, we re-classify Brey 75 as WN6, Brey 81 as directly between an Of and a Wolf-Rayet stage and shows WN8, AB18 (marginally) as WN9, BE294 as WN10 and the a spectral morphology quite distinct from LMC WN9–11 three Henize objects S119, S61, S142 as WN11. Following stars (Crowther & Bohannan 1997). L.F. Smith et al. (1996) we further refine spectral classifica- 4. An extension of the WN sequence to lower excitation also tions of these stars to incorporate hydrogen contents, as sum- mirrors the existing WC sequence. The Planetary Neb- marised in Table 1. No additional WN9 stars are found here ula central star CPD−56◦ 8032, classified [WC10], has al- from the sample of Bohannan & Walborn (1989) since those most identical He i-ii line strengths to the WN10 star S9 objects showing the strongest He ii emission (i.e. highest exci- (Crowther et al. 1996). tation) were all discussed in Paper I. Relative to the Ofpe/WN9 subgroup structure of Walborn (1982), all Group A members One indirect effect of our re-classification is that objects with are identified as WN9 stars, with Group B stars assigned either substantial hydrogen (XH≈20–40%) at their surfaces may not WN10 or WN11 classifications. The spectral appearance of the be consistent with the usual core helium burning definition of a sole Group C member R99 from Walborn (1982) is found to Wolf-Rayet star (Smith 1973). At present, however, the critical be inconsistent with a Wolf-Rayet classification since it lacks link between the observed H/He ratio (when it is greater than the He i P Cygni profiles characteristic of WNL stars and is zero), and the state of the core (hydrogen or helium burning) discussed separately (Sect. 3.6). Wolf-Rayet catalogue numbers is not known. Therefore, while still representing the final phase for these new additions are Brey 37a (BE294), Brey 45a (S119), in massive star evolution, Wolf-Rayet spectral classifications Brey 97a (S142) and Brey 99a (S61). We note that BE294 has may not necessarily imply core helium burning. We note that been identified as a LBV (Bohannan 1989), while S119 has been Galactic hydrogen-rich WN6–7ha (or WN6–7+abs) stars have proposed as a LBV by Nota et al. (1994) because of the simi- been proposed as core hydrogen burning objects (e.g. Rauw et larity of its circumstellar nebula with established LBVs (R127, al. 1996), yet the existence of WR 123, a WN8 star with very AG Car). This is consistent with the findings from Paper I and P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 505

Fig. 2. A spectral comparison of selected rectified AAT–RGO observations of LMC WNL stars including BE381 (WN9h) from Paper I. Successive stars are shifted vertically by 1.5 continuum units, and strong He ii λ4686 profiles are omitted for clarity 506 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI

Fig. 3. Ultraviolet flux cal- ibrated, radial velocity cor- rected, spectra of represen- tative LMC WN6 (Brey 89, IUE), WN8 (Brey 13, IUE), WN9 (Sk−69◦249c, HST) and WN10 stars (BE294, HST). The broad depression in WN9–10 stars is due to Fe iv (Schaerer & Schmutz 1992)

L.J. Smith et al. (1994) that WN9–11h stars generally represent becomes visible. Overall the ultraviolet spectral appearance of either dormant LBVs or the immediate progenitors of classical Brey 89 (WN6h) is similar to the Galactic WN6ha star WN24 Wolf-Rayet (WN8) stars. (HD93131, Paper III), while that of Brey 13 (WN8h) resembles the Galactic WN8 star WR40 (HD 96548, Paper III), except for weaker Fe iv-v lines, and stronger N iv] λ1486 and He ii λ1640 3.2. Optical and ultraviolet spectroscopy emission. In Fig. 2 we present new blue and yellow spectroscopy of se- The ultraviolet spectra of some LMC WN9–10 stars have lected LMC programme WN6–11 stars, sorted by spectral type. previously been discussed by Shore & Sanduleak (1984) and in We show BE381 (Brey 64) from Paper I in preference to AB18 Paper I, but at lower spectral resolution. From Fig. 3 the broad iv1 since its line strengths are more representative of WN9. The pro- depression between λ1500–1700 due to Fe is readily appar- gression to narrower, lower excitation spectral features at later ent. Shore & Sanduleak (1984) gave a UV classification of B1 I ii spectral type is clearly demonstrated; compare He ii λ5412 to for S61, although as for R84 and S9 (Paper I), He λ1640 emis- He i λ5876 or N iv λ4058 to N iii λλ4634–41. sion is present. Since the observed optical excitation of very late WN stars is closer to early B than late O supergiants, this UV Fig. 3 shows representative flux calibrated ultraviolet spec- classification is anticipated. tra of LMC WN6–10 stars, including HST/FOS observations of the WN9h star Sk−69◦ 249c (HDE 269927c, Paper I). As in the optical we see a smooth progression to lower excitation, nar- 3.3. Nebular emission lines rower and weaker emission lines in the ultraviolet from WN6 Many LMC WN9–11 stars show nebular lines superimposed on to WN10. In particular, highly excited transitions such as N v their stellar spectra. Circumstellar nebulae have been discovered λλ1238–42, C iv λλ1548–51 and He ii λ1640 rapidly decrease in strength at later spectral type, while N iii] λλ1747–54 and 1 In Paper I this Fe iv depression (Schaerer & Schmutz 1992) was Si iv λλ1394–1402 increase in strength, and Al iii λλ1855–63 erroneously assigned to Fe ii (following Shore & Sanduleak 1984) P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 507

Fig. 4a and b. AAT-UCLES spectrum of the Hβ profile in S119 show- ing a the observed spectrum with nebular emission lines superimposed. The heavy line represents a Gaussian fit to the nebular and stellar com- ponents. b The underlying stellar emission profile with the nebular component subtracted

around R127 (Walborn 1982; Clampin et al. 1993), S61 (Wal- born 1982; Stahl 1987), S119 (Nota et al. 1994) and BE381 (Nota et al. 1996). In addition, R84, R99 and Sk −69◦249c Fig. 5. MSO observations of the WN11 stars S142, S119 and S61 in the region of Hα and [N ii] showing the stellar and nebular components of show nebular lines but further observations are required to de- ii the emission lines. Dotted-lines indicate underlying stellar components termine if they arise in circumstellar nebulae or H regions for S119 and S61 (Walborn 1982; Nota et al. 1996). While the presence of neb- ulae is of much interest for studying the evolutionary connec- tions between WN9–11, LBV and WN8 stars, and the properties lar lines included) give an erroneously high value of H/He≈4, of the central stars (e.g. L.J. Smith 1995), they pose a severe while the true ratio is H/He∼1.5. problem for the quantitative analysis of the stellar spectrum, We have examined the spectra of other WN9–11 stars in our particularly for determining the H/He ratio. Since the nebulae sample with the aim of assessing if nebular lines are present, are barely spatially resolved, it is very difficult to subtract the and if so, how much of a problem they pose for stellar analysis. nebular emission during data reduction. The best approach ap- In Paper I, we analysed the WN9h star Sk −69◦249c which has pears to be to resolve spectrally the nebular lines and to subtract nebular lines (Walborn 1982; Nota et al. 1996). Unpublished them using Gaussian fitting techniques. High resolution echelle high resolution spectra obtained at the AAT with UCLES show observations of the WN11 star (and LBV candidate) S119 in that the nebula contributes only ∼ 2% of the total flux at Hβ.For the region of Hβ are shown in Fig. 4. As described by Nota et most of the stars in our present sample with nebulae, we have al. (1994, 1996), the front and back of an expanding shell are MSO Hα observations at a spectral resolution of 1 A˚ which is clearly seen expanding at ∼ 26 km s−1. To remove the neb- just sufficient to separate the stellar and nebular components. ular emission, we have used the Gaussian fitting package elf The Hα region is shown in Fig. 5 for S142, S119 and S61. within dipso; Fig. 4a shows the three component Gaussian fit We detect weak [N ii] nebular lines in the spectrum of S142, and Fig. 4b shows the underlying Hβ emission with the nebu- indicating that any nebular contamination of the stellar Balmer lar lines removed. In the Appendix (Sect. A.14) the H/He ratio lines will be negligible. Further observations are required to for S119 is determined using intermediate and high resolution determine if the nebular emission arises in a circumstellar nebula spectra. We find that the intermediate resolution spectra (nebu- or an underlying H ii region. S119, as discussed previously, has 508 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI

Fig. 6. Comparison of recti- fied, radial velocity corrected ultraviolet (HST-FOS) and op- tical (AAT–RGO) spectra of R99 (HDE 249445) with the WN10h star BE294. The lat- ter is shifted vertically by 2 continuum units for clarity. These observations demon- strate the high wind velocity (∼1 050 km s−1), absence of the Fe iv ultraviolet depres- sion and unusual He i profiles for R99 very strong nebular lines. In Fig. 5 the Hα line is just resolved, estimate wind velocities. In the Appendix (Table 6) we present allowing us to separate the two contributions. S61 is known to measurements of wind velocities for our programme stars. Al- have an associated nebula (Walborn 1982; Stahl 1987). From the though wind velocities are not readily measured from low reso- Gaussian fits to Hα shown in Fig. 5, we find that ≥ 75% of the lution IUE data, measurements resulting from the approximate flux is nebular. We find that the true H/He ratio for S61 is ∼1.2 method of Prinja (1994) appear to be broadly consistent with whereas assuming that the Balmer lines are purely stellar gives those resulting from optical profiles. BE294 shows several for- H/He≈6 (Appendix, Sect. A.16). For the two remaining stars bidden transitions ([Fe iii] λ4658, λ5270, [N ii] λ5755) in its with known nebular lines R84 and BE381, the high resolution visual spectrum (Fig. 2). The measured half width at zero inten- spectra of Nota et al. (1996) show that the nebular emission is sity of these profiles is in excellent agreement with the veloci- negligible. Finally we note that IR analyses of LMC WN9–11 ties from He i P Cygni profiles, as was previously found for S9 stars based on line ratios involving a hydrogen line (e.g. Brγ) (Sk−66◦ 40, also WN10) in Paper I. For comparison in Table 6, should be treated with caution if the star has strong nebular lines we include measurements previously tabulated by Koesterke et (e.g. S119 and S61). al. (1991) and Rochowicz & Niedzielski (1995). In Sect. 4 mi- nor adjustments are made to these wind velocities in order to optimise line profile fits. 3.4. Line measurements and wind velocities In the Appendix (Table 7) we present equivalent width and Determinations of wind terminal velocities in hot luminous stars FWHM measurements for selected optical emission lines for are best suited to observations of UV metal resonance lines all programme stars (including those from Paper I) based on (Prinja et al. 1990) or infrared He i P Cygni profiles (Eenens & our AAT and MSO observations. Koesterke et al. (1991) have Williams 1994). For the few stars with high resolution UV obser- previously presented intermediate dispersion He i λ5876 and vations, we can measure terminal velocities from the bluemost He ii λ5412 profiles for four WN6–8 stars in common with our absorption edge of Si iv λλ1393–1402 or C iv λλ1548–1551. sample, while Nota et al. (1996) have recently presented high For the majority of our programme stars, for which we only have dispersion optical spectra for two WN10–11 programme stars. optical observations, we use instead the He i λ5876 profile to We find good agreement with the published equivalent widths P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 509 of Koesterke et al. (1991), while we obtain higher equivalent clearly absent in R99. Shore & Sanduleak (1984) commented widths than Nota et al. (1996), especially for strong optical lines. on its probable UV emission line variability and assigned an ultraviolet B0.5 supergiant classification. From its ultraviolet 3.5. Photometry and interstellar reddenings properties, R99 therefore appears to be of higher excitation, but lower wind density than typical WN9–11 stars. We will Since only eight programme stars have narrow band optical defer any further discussion to a future paper, but we note an photometry (Torres-Dodgen & Massey 1988) we utilise wide overall optical and near-infrared spectral similarity of R99 to the band B and V photometry taken from a variety of sources. peculiar LBV candidate HD 5980 (Sk 78) in the SMC during These are typically within 0.05 mag of narrow band measure- 1994 December. ments for WNL stars. Optical and infrared photometry is pre- sented in the Appendix (Table 8) for our programme stars. As in 4. Model results Paper I we have derived interstellar reddenings by combining theoretical energy distributions with UV, optical and IR pho- In this section we summarise the technique used while we de- tometry. For this a uniform Galactic foreground extinction of scribe the results of our model fits for individual stars in Ap- 0.05 mag was assumed, which was combined with the stan- pendix A. Further details of the model atmosphere used, diag- dard LMC extinction curve (Howarth 1983) and an extinction nostic lines employed, and the method adopted to obtain optimal ratio of R=AV/EB−V=3.2 (Olson 1975). Comparison between line profile matches are described at length in Paper I. the interstellar reddenings derived here and the arithmetic mean values resulting from the previous determinations of L.J. Smith 4.1. Technique & Willis (1983), Schmutz & Vacca (1991) and Morris et al. (1993a) shown in the Appendix (Table 8) is generally within The model calculations are based on the iterative technique of 0.02 mag. Hillier (1987, 1990) which solves the transfer equation in the For consistency with Paper I, we adopt the standard LMC co-moving frame subject to statistical and radiative equilibrium, distance of 51.2 kpc from Panagia et al. (1991), corresponding assuming an expanding, spherically-symmetric, homogeneous to a distance modulus of 18.55 mag. Use of the latest LMC and static atmosphere. The stellar radius (R∗) is defined as the distance estimate of 47.3 kpc by Gould (1995) would result in inner boundary of the model atmosphere and is located at Rosse- uniform reduction in MV by 0.18 mag. land optical depth of ∼20 with the stellar temperature (T∗) de- fined by the usual Stefan-Boltzmann relation. Similarly, the ef- 3.6. The peculiar emission line star R99 fective temperature (Teff ) relates to the radius (R2/3) at which the Rosseland optical depth equals 2/3. We adopt the usual β=1 Before we move onto our theoretical model results, we turn velocity law for all our analyses. briefly to the related LMC object R99. This star has received For the present application, the adopted model atom incor- considerable attention because of its emission line characteris- porates 10 levels of H i (n ≤10), 16 of He ii (n ≤16) and 39 tics in the ultraviolet (Shore & Sanduleak 1984), optical (Stahl et levels of He i (n ≤ 14), and is almost identical to that used al. 1984; Stahl 1986) and infrared (McGregor et al. 1988). R99 in Paper II. Although metal abundance determinations are not was recognised by Walborn (1977, 1982) as being unique in its considered here, we also incorporate simplified atoms of carbon spectral morphology due to the near-absence of optical absorp- (C iii-iv) and nitrogen (N ii-v) since these have a dominant ef- tion features and thus is essentially ‘unclassifiable’. Neverthe- fect on the cooling of the wind (Hillier 1988). For this study less, R99 was later included in the LMC Ofpe/WN9 subgroup we adopt carbon and nitrogen abundances of N/He=0.0025, by Bohannan & Walborn (1989). In Fig. 6, we compare our op- C/N=0.1 which represent mean values for the LMC WN9–10 tical observations of R99 with the WN10h star BE294. While stars from Paper I. In total, 95 individual levels and 521 non- the He i-ii and H i emission of R99 is consistent with a WN10h LTE transitions are simultaneously considered. classification, the observed He i profiles are peculiar in that the Following Papers I–III, diagnostic He i (λ5876), He ii usual sharp P Cygni absorption components are absent, but shal- (λ4686 or λ5412) and H i (Hβ,Hα) lines are used to deter- low, violet absorption extending to ∼1 050 km s−1 is observed. mine the stellar parameters. While the He ii diagnostic is usually AAT–UCLES observations of R99 prohibit a sharp, nebular ori- λ5412, we use λ4686 instead for very low excitation Wolf-Rayet gin for He i-ii or H i and confirm an asymmetric He ii λ4686 stars (WN9–11) because of the weakness of the former. As dis- feature, which can be reproduced with a double Gaussian com- cussed in Sect. 3.3, the availability of AAT–UCLES and MSO– prising a narrow He ii λ4686 feature with FWHM∼300 km s−1 coude´ observations for S119 and S61 allows a further test of our plus a broad component (FWHM∼600 km s−1) centered at results for those (typically WN11) stars with possible Balmer +340 km s−1. line nebular contamination. Radial velocities for individual stars HST-FOS observations of R99 are also presented in Fig. 6 are obtained from line profile fits (σ∼20 km s−1). and reveal strong, broad absorption profiles (e.g. C iv λλ1548– Uncertainties in the derived physical parameters for WNL 51), corresponding to an unusually high terminal wind velocity stars have previously been described in Papers I–II, in which we of ∼1 050 km s−1. The broad ‘depression’ between λλ1500– have also investigated the effect of line blanketing. In particu- 1700 due to Fe iv observed in WN9–11 stars (see Fig. 3) is lar, inconsistencies between hydrogen-helium and metal anal- 510 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI

Table 2. Derived stellar parameters for the programme LMC WN6–11 stars, including four WN9–10 stars from Paper I (indicated by ∗). Two entries are given for S119: Model A using our AAT–RGO spectra including Balmer nebular contributions and Model B, based on our AAT–UCLES and MSO–coude´ spectra,. with Balmer nebular contaminations removed. We include Lyman continuum ionising photons, Q0 and wind performance numbers, [(Mv∞)/(L∗/c)]

. . Star Alias Sp. T? R? Teff R2/3 log L log Mv∞H/He log Q0 Mv∞ (B−V)0 MV −1 −1 −1 Type kK R kK R? L M yr km s s L∗/c mag mag Brey 24 FD23 WN6h 36.4 12.6 32.9 1.22 5.40 −4.60 950 1.50 49.1 4.7 −0.30 −5.4 Brey 26 HD 36063 WN6(h) 35.3 16.9 31.0 1.30 5.60 −4.12 1500 0.40 49.3 13.8 −0.28 −6.0 Brey 47 FD42 WN6h 35.7 11.4 32.9 1.18 5.28 −4.70 900 1.30 49.0 4.7 −0.30 −5.1 Brey 75 R134 WN6(h) 33.1 25.9 30.8 1.15 5.86 −4.11 1300 0.20 49.5 6.8 −0.34 −6.7 Brey 89 R144 WN6h 31.8 43.9 26.7 1.42 6.25 −3.65 1500 1.00 49.9 9.3 −0.28 −7.7 Brey 90 R145 WN6(h) 31.8 39.5 28.5 1.25 6.16 −3.84 1350 0.70 49.8 6.6 −0.30 −7.4 Brey 71 HDE 269883 WN7h 39.4 9.4 29.4 1.79 5.28 −4.35 1000 1.00 49.0 11.6 −0.21 −5.1 Brey 80 R135 WN7h 36.1 15.2 24.6 2.15 5.55 −3.70 1800 0.80 49.2 49.9 −0.18 −6.2 Brey 13 HD 33133 WN8h 34.8 16.7 26.0 1.79 5.57 −4.14 850 1.45 49.2 8.2 −0.22 −6.1 Brey 36 FD32 WN8h 33.7 13.4 31.0 1.18 5.32 −4.74 650 1.70 48.9 2.8 −0.31 −5.4 Brey 81 AB11 WN8(h) 32.4 27.0 27.8 1.36 5.86 −4.02 850 0.20 49.5 5.5 −0.28 −6.8 R84∗ HDE 269227 WN9h 28.5 33.8 24.9 1.31 5.83 −4.40 400 2.50 49.3 1.2 −0.30 −7.0 AB18 Brey 44a WN9h 30.9 20.0 30.1 1.05 5.52 −5.01 520 1.90 49.0 0.8 −0.34 −6.0 BE381∗ Brey 64 WN9h 30.6 20.8 27.5 1.25 5.54 −4.65 375 2.00 49.1 1.2 −0.30 −6.2 Sk−69 249c∗ HDE 269927c WN9h 30.0 26.3 27.7 1.17 5.70 −4.51 500 1.75 49.2 1.5 −0.32 −6.6 S9∗ Sk−66◦ 40 WN10h 29.7 20.5 20.8 2.04 5.47 −4.47 300 3.50 48.9 1.7 −0.23 −6.2 BE294 HDE 269582 WN10h 29.2 30.3 22.0 1.76 5.78 −4.30 300 1.90 49.3 1.2 −0.25 −6.9 S119 HDE 269687 WN11h A 27.9 32.6 26.2 1.14 5.76 −4.87 230 (4.00) 49.2 0.3 −0.35 −6.9 B 27.8 34.0 27.0 1.06 5.80 −4.92 230 1.50 49.2 0.2 −0.33 −6.9 S142 BE470 WN11h 28.4 28.4 25.4 1.25 5.67 −4.80 220 3.00 49.1 0.4 −0.30 −6.6 S61 BE153 WN11h 28.3 33.3 27.6 1.05 5.76 −4.96 250 1.20 49.2 0.2 −0.33 −6.8

yses suggest that stellar temperatures and luminosities are un- here. As discussed in Paper II for Galactic WNL stars, bolomet- derestimated using non-blanketed hydrogen-helium models. In ric corrections incorporating hydrogen and metals are typically the extreme case of WR25 (HD 93162 WN6ha), use of a ni- ∼0.2 mag higher than pure helium models, while stellar and trogen rather than hydrogen-helium analysis, led to significant ionizing photon luminosities are ∼0.2 dex higher. increases in stellar luminosity (0.2 dex), bolometric correction (0.6 dex), H0 ionizing photon luminosity (0.5 dex), and stellar temperature (7 000K). It is hoped that future studies incorpo- 5. Discussion rating line blanketing will reconcile such differences. Never- In this section we compare various properties of LMC WNL theless, since we currently follow an identical approach to Pa- stars with their Galactic counterparts and discuss the evolution- pers I–II, we are confident that internal comparisons of funda- ary implications of our results. mental parameters for Galactic and LMC stars remain valid. Future photoionization model studies of WR nebulae (e.g. Es- teban et al. 1993) would provide a rigorous check on theoretical 5.1. Comparison of Galactic and LMC WNL stars predictions. We consider first if the LMC WNL stars show any evidence for Line profile fits to diagnostic lines are presented in the Ap- a lower metallicity in their observed spectra compared to the pendix (Figs. 7-10) where we also discuss individual objects, Galactic WNL stars. If we can demonstrate that the LMC stars arranged in increasing WNL subtype. in our sample are of lower metallicity, then we can investigate The derived stellar parameters for our programme stars are what effect this has on the parameters derived in Sect. 4. In presented in Table 2 and compared with previous Escape Proba- Fig. 7, we show the equivalent width ratio of N iii λ4640/N iv bility Method (L.J. Smith & Willis 1983) and pure helium stan- λ4058, which is purely an indicator of spectral excitation, plot- dard model (Koesterke et al. 1991, Vacca 1992) analyses in ted against the metallicity indicator N iii λ4640/He ii λ4686. Table 3. Overall we find slightly higher stellar luminosities rel- It is apparent that the LMC stars (particularly the WN6–7 sub- ative to pure helium analyses, although this effect is enhanced types) have weaker N iii/He ii ratios compared to their Galactic due to the somewhat higher absolute visual magnitudes obtained counterparts and thus appear to have lower metallicities. This P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 511

Table 3. Comparison of stellar parameters derived here (CS) with pre- vious analyses (L.J. Smith & Willis 1983 SW; Koesterke et al. 1991 KHSW; Vacca 1992 WDV)

. star T? T2/3 R? log L log M H/He v∞ MV −1 −1 kK kK R L M yr km s mag Brey 13 CS 35 26 17 5.6 −4.1 1.4 850 −6.1 SW 34 12 5.2 1.2 1300 KHSW 33 30 15 5.3 −4.4 1000 −5.8 WDV 32 17 5.4 −3.8 −5.9 Brey 24 CS 36 33 13 5.4 −4.6 1.5 950 −5.4 SW 36 11 5.3 1.1 1500 KHSW 33 32 13 5.2 −4.5 1200 −5.2 Brey 26 CS 35 31 17 5.6 −4.1 0.4 1500 −6.0 SW 38 14 5.5 0.8 2000 KHSW 33 31 17 5.5 −4.2 1600 −5.9 Brey 36 CS 34 31 13 5.3 −4.7 1.7 650 −5.3 WDV 31 15 5.2 −4.3 −5.4 Brey 47 CS 36 32 11 5.3 −4.7 1.3 900 −5.1 KHSW 34 33 10 5.1 −4.8 900 −4.7 Fig. 7. The equivalent width ratio of N iii λ4640/N iv λ4058 plot- WDV 31 10 5.0 −4.5 −4.6 ted against N iii λ4640/He ii λ4686 for Galactic (open) and LMC Brey 80 CS 36 25 15 5.5 −3.7 0.8 1800 −6.1 (filled-in) WN6–9 stars. Observational data for Galactic stars are from WDV 34 15 5.4 −3.7 −5.9 Paper III and our own measurements from Hamann et al. (1995b) Brey 89 CS 32 27 44 6.2 −3.6 1.0 1500 −7.7 SW 29 37 5.9 1.1 1300 Brey 90 CS 32 28 39 6.2 −3.8 0.7 1350 −7.4 SW 36 30 6.1 0.6 1300 rently one WN11 star (He 3-519). We note however that the distinction between WN8 and WN9 spectral classifications is often fairly subjective, as shown in Fig. 1a. For example, several Galactic WN8 stars (e.g. WR130, WR156) show N iii λ4640 a iv cannot be a result of the LMC stars having a different exci- factor of thirty times stronger than N λ4058 (recall Fig. 7), iv tation (i.e. weaker N iii) because they show the same range of but fail a WN9 classification because the strength of N λ4058 N iii/N iv ratios for a given subtype. Likewise, Fig. 1 shows that is non-negligible. WN9 classifications may therefore be more the LMC and Galactic stars have similar He ii λ4686 emission suitable for these objects. Another difficulty with accurately line strengths. This is in contrast to the study of L.J. Smith & classifying Galactic WN8 stars is that strong interstellar ex- iv Willis (1983) who found that He ii λ4686 in LMC WN stars tinction often prevents reliable N λ4058 measurements, in was twice as strong as that in Galactic WN stars. We find that contrast to the lightly reddened LMC stars. their equivalent widths for the five stars in common are 20– We now examine if the terminal velocities v∞ of the LMC 50% larger than those given in the Appendix (Table 7). This stars are lower than the Galactic WNL stars. Haser et al. (1994) coupled with the re-classification of their four LMC WN7 stars and Walborn et al. (1995a) have found that O stars in the LMC to WN6, and more measurements of Galactic WN8 stars (they have marginally slower winds than their Galactic counterparts, only used WR40 for comparison) appears to explain the dis- as anticipated from theory. In Fig. 8 we plot v∞ against stellar crepancy. The inference from Fig. 7 that the spectra of LMC temperature T∗. There is a definite trend (with a fair amount of WNL stars indicate a lower nitrogen content than Galactic stars scatter) for a decreasing v∞ with decreasing T∗. Stars with a is quantitatively confirmed in Paper I. We find that the average high v∞ for their T∗ are anomalous in some way. The Carina nitrogen mass fraction is 0.6% which is identical to that pre- WNLa stars appear to be on a different evolutionary track and dicted by Schaerer et al. (1993) for a WNL star with Z =0.008. are more like extreme O stars (Paper III). The four 30 Dor mem- In addition, the UV Fe iv-v line spectrum of Brey 13 (Fig. 3) bers, Brey 75, 80, 89 and 90 have very high luminosities, and is significantly weaker than Galactic WN8 stars. Brey 26 may be a close binary. Omitting these stars, there is no One interesting difference between the two galaxies is the evidence that the WN6–8 stars in the LMC have lower veloc- relative populations of WN9–11 and their evolutionary succes- ities than their Galactic counterparts. The cool WN9–11 stars sors, the WN8 stars. In the LMC we find only three WN8 stars with log (T∗/K)≤4.5 may have winds that are ∼ 40% slower compared to nine WN9–11 stars, whereas in the Galaxy, there but with only three Galactic WN stars in this group, this must are ∼12 WN8s, one normal WN9 star (WR105, NS4) and cur- be regarded as uncertain. 512 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI

Fig. 8. A comparison of terminal wind velocities (km s−1) versus stellar temperature for Galactic (open symbols) and LMC (filled-in symbols) WNL and LBVs. The adopted terminal velocity for WR66 (HD 134877, WN8(h)) is 650 km s−1 based on pre- viously unpublished optical spectroscopy, instead of 1500 km s−1 as adopted by Hamann et al. (1995a)

We now compare the luminosities of WNL stars in the LMC wind performance number2 is plotted against the atmospheric and Galaxy by showing their positions in the H-R diagram in hydrogen content. The two parameters show a reasonable corre- Fig. 9a. With the exception of the highly luminous 30 Dor WN6 lation in the sense that the wind performance number increases stars Brey 89 and 90, we see no separation between Galactic as the star becomes more evolved i.e. the amount of helium in and LMC WNL stars, in contrast to the claim of Koesterke et the wind increases. Stars with a hydrogen content of ≤ 20% are al. (1991) who found that the LMC stars were less luminous. If all WN6–8 stars and have high values of η from 3–20, and 50 we were to restrict our comparison to WN6–8 stars, however, in the case of the extreme 30 Dor star Brey 80. There appears excluding 30 Dor members because of potential multiplicity, it to be no difference between Galactic and LMC WN6–8 stars. is possible that the remaining LMC stars might possess lower Conversely, the region with XH ≥ 30% is occupied by LMC luminosities, although the distances to many Galactic WR stars, WN9–11 stars and two Galactic LBVs. All these stars have and hence their luminosities, remain uncertain. η ∼< 1 and can be considered to have radiatively-driven winds. Since He ii λ4686 line luminosity determinations are impor- It is also clear that the Galactic WNLa stars form a distinct tant for studies of WR starburst regions, we note that the aver- group with high performance numbers and hydrogen contents. This diagram can be interpreted as an evolutionary sequence age He ii λ4686 line luminosity is 415 L , (range 90–1 700 L ) based on 14 LMC WN6–9 stars. For comparison, from 11 Galac- with the wind performance number increasing with the helium content. Hamann et al. (1995a) suggested a relation between tic WN6–9 stars with known distances, the average He ii λ4686 . hydrogen mass fraction and log M−log L1.5 for Galactic WN line luminosity is 215 L (range 50–440 L ). Although the most luminous Galactic WNL stars show progressively weaker stars (their Fig. 7). Inclusion of LMC WN stars broadly con- emission lines, this is not true for LMC WNL stars (in contrast firms their derived relation, though with significant scatter. to Morris et al. 1993b). Current radiatively-driven wind theory (Kudritzki et al. 5.2. Stellar Evolution 1989) predicts that mass-loss should scale as the square-root of There are a number of well known problems in comparing cur- the metallicity. This suggests typical LMC WNL stars ought to rent single star evolutionary models with atmospheric analyses have mass-loss rates 0.2 dex lower than Galactic examples if the (see e.g. Hamann 1994). In addition, it is now recognised that WR winds are radiatively-driven, as has recently been found, rotational mixing has a significant effect on evolutionary mod- albeit marginally, for LMC O supergiants relative to Galactic els (Fliegner & Langer 1995; Langer, priv. comm.), allowing stars by Puls et al. (1996). Further, assuming that WR winds are for instance, surface chemical enrichment at a relatively early driven by multiple scattering, we might expect their momentum 2 . rates to scale with the number of optically thick lines, and so be The wind performance number (η=Mv∞/[L/c]) is the factor by proportional to metallicity (e.g. Gayley 1995). In Fig. 9b, the which the single scattering limit is exceeded P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 513

Fig.9.aObserved H-R diagram for Galactic (open symbols) and LMC (filled-in symbols) WNL and LBVs; b Derived wind performance numbers, η, for WNL stars versus surface hydrogen content (by mass). Physical parameters are taken preferentially from Pa- pers I–III, L.J. Smith et al. (1994), L.J. Smith et al. (1995), and supplemented by the analyses of Hamann et al. (1995a) post-main sequence phase for sufficiently massive stars. Nev- We have previously proposed that high initial mass stars ertheless, inspection of the results from the latest evolutionary (Minit∼>40M ) advance through a LBV stage, with WN9–11 models (Meynet et al. 1994) suggests that at low metallicities, probably dormant LBVs during their hot phase, before progress- WR formation should be restricted to higher initial mass, higher ing on to WN8 stars (Smith et al. 1994; Papers I, III). Consider- luminosity progenitors, because of lower mass-loss rates, with ing first the relationship between WN9–11 and LBV stars, we the WR lifetime also reduced. find that the stellar luminosities (log L ∼5.5–5.8) and helium 514 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI

Fig. 10a and b. Morphological sequences amongst post-main sequence massive stars between λλ4000–4900. a Sequence from the B supergiant LBV P Cygni through WN9–11 stars to the classical WN8 star Brey 36. b Sequence from the O3 supergiant HD 93129A, through Sk−67◦ 22 (O3 If/WN6) and WR25 (HD 93162, WN6ha) to the WN6h star Brey 89. LMC spectra are radial velocity corrected (for the purpose of comparison). H/He ratios are taken additionally from Papers I–II, Langer et al. (1994) and Kudritzki et al. (1991). All data are plotted to the same scale, shifted vertically for clarity P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 515 contents (55–75% by mass) of the WN9–11h stars (incorporat- Overall, we find that while there is observational evidence ing results from Paper I) are in close agreement with the LBV for a lower metal content in LMC WNL stars, this does not R71 in the LMC (Lennon et al. 1994). We note that BE294 seem to affect the stellar parameters in comparison to Galactic has been identified as a LBV (Bohannan 1989), while R127 WNLs. In particular the predicted dependence of metallicity on (HDE 269858f) was the prototype of the Ofpe/WN9 subclass in wind strength is not seen although the high performance num- 1977 (probably WN11h at that epoch) before its discovery as a bers of the WN6–8 stars question the application of radiation- LBV (Stahl et al. 1983). The association of circumstellar ejecta driven mass-loss theory to Wolf-Rayet stars. We find tentative nebulae with several LMC WNL stars allows further support of evidence that the radiatively-driven winds of the WN9–11 stars this evolutionary scenario. For example, the WN8 star Brey 13 have lower terminal velocities than the few Galactic examples. has an ejecta-type nebula (Garnett & Chu 1994), while LBV- The observed properties of LMC WNL stars support our previ- type nebulae associated with several WN9–11 stars (e.g. S119, ous evolutionary schemes involving direct evolution to WN6–7 S61) provide further evidence for a close link with LBVs (e.g. stars from the most massive O stars, located in starburst regions. R127). In contrast, less massive O stars advance through an intermedi- In Fig. 10a we illustrate this evolutionary sequence by show- ate LBV phase, with Ofpe/WN9 stars, now revised to WN9–11, ing the smooth progression of spectral morphology with in- representing a hot dormant LBV stage, and subsequently evolve creasing excitation and wind velocity (and decreasing hydro- to a classical WN8 star. gen content) between B-supergiant LBVs and WN11–8 stars. Observations of P Cygni were obtained at the William Herschel Acknowledgements. We thank John Hillier for providing both his stel- Telescope in 1993 October using the Utrecht echelle spectro- lar atmosphere code and useful IR photometry. We are grateful to Allan graph. We note that WN8–11 stars are found in the field in Willis and Lindsey Smith for their contributions to successful telescope applications, and to Ian Howarth and Angela Cotera who kindly let us the LMC (with the exception of the hydrogen-poor WN8 star take a peek at their IR spectra of Brey 89. PAC and LJS acknowledge Brey 81), suggesting that their initial masses are lower than the financial support from PPARC. Calculations have been performed at WN6–7 stars located in 30 Dor. the CRAY Y-MP8/128 of the RAL Atlas centre and at the UCL node of We find that the luminosities of LMC WNL stars span a the U.K. STARLINK facility. We appreciate the support of the staff of similar range to Galactic WNL stars, suggesting a similar range the Mount Stromlo and Anglo-Australian Observatories, particularly of initial masses. While stellar luminosities of most WN6–7 over two Christmas periods for the latter. We have used observations stars are unexceptional, the 30 Doradus WN6 stars Brey 89 made with the NASA/ESA Hubble Space Telescope, obtained from the and Brey 90 have extreme luminosities (log (L/L )∼6.2). The data archive at the Space Telescope Science Institute. STScI is oper- spectral synthesis study of 30 Dor by Vacca et al. (1995) has ated by the Association of Universities for Research in Astronomy, Inc. shown that the age of the starburst is at most ∼3 Myr. Examina- under the NASA contract NAS 5–26555. This work has also made use of the SIMBAD database, operated at the CDS, Strasbourg, France. tion of the evolutionary models of Meynet et al. (1994) implies that only stars with initial masses of ∼90–110 M will be WNL stars by this time. In Paper III we found that the Carina WNLha Appendix: results for individual stars stars, with high stellar luminosities, were closely related to, and A.1. Brey 24 (FD23, WN6h) directly descended from, massive Of stars, with WN6–7 suces- sors. This result has recently been supported by the direct mass Brey 24 whose spectral type has recently been revised from determination of ≥72 M by Rauw et al. (1996) for HD 92740 WN7 to WN6 (L.F. Smith et al. 1996) is located in the OB (WR22, WN7ha) and the presence of spectroscopically similar association LH45. The derived parameters (T∗∼36kK, log . −1 stars in the young cluster NGC3603 (Drissen et al. 1995). We (M/(M yr )) ∼−4.6, log (L/L )∼5.4) from our profile fits find similar evidence here that (at least some) WN6–7 stars are (Fig. 11) are fairly consistent with previous determinations as descended from very massive progenitors, probably involving shown in Table 3, while we obtain a slightly higher hydrogen direct evolution from O3 If/WN6 stars as proposed in Paper III. content of H/He∼1.5, relative to L.J. Smith & Willis (1983). The O3 If/WN6 stars, also located in and around 30 Dor (Wal- born 1994), probably represent LMC equivalents of the Galactic A.2. Brey 26 (HD 36063, WN6(h)) WNLha stars, due to their similar spectral morphologies and ex- treme stellar properties (Pauldrach et al. 1994). Brey 26 is another star whose spectral appearance has recently We illustrate the evolutionary sequence for the most massive been revised to WN6 from WN7 (L.F. Smith et al. 1996). Al- stars in Fig. 10b, which shows the progression of spectral mor- though Brey 26 closely resembles Brey 24, its wind is faster −1 . −1 phologies with increasing emission strength, width and helium (v∞∼1500 km s ), denser (log (M/(M yr )) ∼−4.1) and content between early Of stars and WN6–7 stars. Observations more enhanced in helium (H/He∼0.4) as shown in Fig. 11. of HD 93129A were obtained at the MSO 1.9m in 1995 June A comparison with previous studies is presented in Table 3. using the coude´ spectrograph, while those of Sk−67◦ 22 were Brey 26 shows rapid (∼1.9 days) radial velocity and photomet- taken at the AAT in 1994 December using the RGO spectro- ric variations (Moffat 1989; Seggewiss et al. 1991) indicating graph. Although the chemical content of Sk−67◦ 22 is uncer- either a close binary system or significant intrinsic variability. tain, other O3 If/WN6 stars show negligible helium enrichment Since no photospheric absorption lines are present, it is possible (Pauldrach et al. 1994; de Koter et al. 1994). that this star has a compact companion. In the absence of any 516 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI quantitative information about the possible companion, we have this star shows radial velocity variability. Moffat (1989) tenta- assumed that the visual spectrum of Brey 26 is entirely due to tively identified a long spectroscopic period of 25 days. Should the Wolf-Rayet star. this be confirmed, the stellar parameters of Brey 90 will require revision although given its visual magnitude (MV=−7.43), it is A.3. Brey 47 (FD42, WN6h) unlikely that the derived values would be significantly affected.

Brey 47, whose spectral type has recently been revised from A.7. Brey 71 (HDE 269883, WN7h) WN8 to WN6h (L.F. Smith et al. 1996) closely resembles Brey 24 both in its visual appearance (see Fig. 11) and Turning now to the WN7 stars, Brey 71 has been little studied . −1 derived parameters (T∗∼35kK, log (M/(M yr )) ∼−4.7, because of its location within the core of 30 Doradus. Brey 71 ii log (L/L )∼5.3). From Table 3 our results are broadly con- shows the strongest He signature of our programme stars sistent with Koesterke et al. (1991) and Vacca (1992). and therefore has the highest stellar temperature (T∗∼39kK), and smallest stellar radius, with typical mass-loss rate (log . −1 (M/(M yr )) ∼−4.4) and luminosity (log (L/L )∼5.3). De- A.4. Brey 75 (R134, WN6(h)) spite the high stellar temperature, the derived hydrogen content The spectral type of Brey 75 is revised from WN7 to WN6 in of H/He∼1.0 is typical of our WNL sample. Line profile fits are Sect. 3.1. This star, located within the core of 30 Doradus, is shown in Fig. 12. highly luminous (log (L/L )=5.9). Moffat (1989) was unable to find evidence for multiplicity in this object. Line profile fits A.8. Brey 80 (R135, WN7h) (Fig. 11) result in typical WN6 stellar parameters except for a Brey 80, also located within the core of 30 Doradus, has a pe- low hydrogen content of H/He=0.2±0.2. culiar spectral appearance among the WNL stars with strong, broad non-Gaussian profiles. The derived stellar parameters for A.5. Brey 89 (R144, WN6h) Brey 80 are unexceptional except for an enormous mass-loss . −1 rate (log (M/(M yr )) ∼−3.7). In particular, we find a wind Brey 89 is another 30 Doradus member and is visually the performance number of fifty for Brey 80 and a mechanical lumi- brightest single Wolf-Rayet star in the LMC with a spectral clas- . nosity ( 1 Mv2 ) of around 15% that of the radiative luminosity. sification recently revised from WN7 to WN6. Overall agree- 2 ∞ Such quantities have previously been exclusive to WNE and ment between theoretical and observed profiles is reasonably WC stars (Howarth & Schmutz 1992). Although profile fits are good (Fig. 11). While the spectrum of Brey 89 does not ap- reasonable (see Fig. 12), improved fits to He ii and H i (though pear to be unusual (Fig. 2) this star possesses an enormous not He i) can be achieved using a slower velocity law (β∼3) stellar luminosity (log (L/L )∼6.25), a factor of two greater which alters the derived stellar temperature and radius, though than the most luminous Galactic WNL star thus far analysed not the mass-loss rate or luminosity. The derived hydrogen con- (WR25, WN6ha; Paper II), and corresponding high mass-loss . −1 tent of H/He∼0.8 for Brey 80 is therefore less reliable than for rate of log (M/(M yr )) ∼−3.6. The radial velocity derived other WN6–7 stars due to the difficulty in modelling its Balmer for Brey 89 (Table 7) agrees well with that (267 km s−1) deter- profiles. mined by Moffat (1989), while H/He∼1.0 is unremarkable rel- ative to other LMC WNL stars. A comparison with the previous study of L.J. Smith & Willis (1983) is shown in Table 3. From A.9. Brey 13 (HD 33133, WN8h) 0 0 our present analysis we obtain H and He ionizing photon lu- Brey 13, the standard WN8 star of the LMC, is prob- −1 −1 minosities of log (Q0)=49.85 s and log (Q1)=49.05 s , typi- ably single (Moffat 1989) and has an ejecta ring neb- cal of an O5.5 supergiant (Vacca et al. 1996). Incidentally, our ula (Garnett & Chu 1994). The derived stellar parameters . −1 synthetic spectrum of Brey 89 also reproduces observed ultravi- (T∗∼34kK, log (M/(M yr )) ∼−4.1, log (L/L )∼5.6), ii i ii olet (He λ1640) and infrared (He 1.083µm, He 1.012µm, chemistry (H/He∼1.4 by number) and spectral appearance of 1.163µm) line profiles, the latter from I.D. Howarth (private Brey 13 are remarkably similar to the Galactic WN8 star WR40 communication). (HD 96548, Paper II), as is its ejecta plus wind blown nebula, enriched in nitrogen (L.J. Smith et al. 1985; Garnett & Chu A.6. Brey 90 (R145, WN6(h)) 1994). Profile fits are shown in Fig. 12 and show good agree- ment with observation, except for the weak P Cygni absorption Brey 90 located near to Brey 89 in 30 Doradus closely resem- component observed at He ii λ5412. Our results show reason- bles its neighbour and has also been revised to WN6 from WN7 able agreement with previous determinations (Table 3). by L.F. Smith et al. (1996). The stellar parameters of Brey 90 based on profile fits (Fig. 12) compare closely with Brey 89 ex- A.10. Brey 36 (FD32, WN8h) cept for a slightly lower luminosity (log (L/L )∼6.16), mass- . −1 loss rate (log (M/(M yr )) ∼−3.8) and hydrogen content Brey 36 is another well known LMC WN8 star. Relative to (H/He∼0.7), while Table 3 shows a comparison with the pre- Brey 13, the emission spectrum of Brey 36 is significantly vious analysis of L.J. Smith & Willis (1983). Unlike Brey 89, weaker and narrower, resulting in a low wind velocity (650 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 517

−1 . −1 km s ) and mass-loss rate (log (M/(M yr )) ∼−4.7), uses our AAT–RGO spectra including Balmer nebular con- although a similar stellar temperature and helium content tamination; and Model B is based on our AAT–UCLES and (H/He∼1.7) are derived (see Table 2). Our derived parameters MSO–coude´ spectra, with Balmer nebular contamination re- are fairly consistent with Vacca(1992) while we obtain a high ra- moved (see Fig. 4a and b). The derived stellar parameters for dial velocity of ∼350 km s−1 from our line profile fits (Fig. 12). both models of S119 are shown in Table 2, and profile fits are presented in Fig. 14. Overall, the narrow, weak emission line A.11. Brey 81 (AB11, WN8(h)) signature of S119 results in a low stellar temperature (∼28kK), . −1 mass-loss rate (log (M/(M yr )) ∼−4.9) and wind velocity Brey 81 represents the third (and final) LMC WN8 star. Another (∼230 km s−1) for both models with a wind momentum that Wolf-Rayet star close to the core of 30 Doradus, Brey 81 was does not exceed the single scattering limit. We are unable to si- found to be multiple by Parker (1993), although our observed multaneously reproduce the Balmer profiles in Model A since line strengths for this star do not indicate significant contamina- the relative stellar and nebular components behave differently tion by its (unseen) companion. Relative to the other LMC WN8 for different lines. Using Hγ, H/He≈4 is obtained for Model A, stars, Brey 81 shows a high luminosity (log (L/L )=5.9) and while a reliable value of H/He∼1.50 is obtained for Model B. Fi- very low hydrogen content of H/He∼0.2 (∼5% by mass), and nally, while Model B predicts marginally stronger He i 2.058µm is thus similar to the hydrogen-poor Galactic WN8 star WR123 emission than Brγ, the observed He i/Brγ flux ratio is 3 (Blum (HD 177230, Paper II). et al. 1995) which presumably includes a nebular contribution for Brγ. A.12. AB18 (Brey 44a, WN9h) This star, discovered by Azzopardi & Breysacher (1985) and A.15. S142 (BE470, WN11h) originally classified WN8–9, marginally falls into the WN9h S142 is another star revised from Ofpe/WN9 to WN11h with category. Relative to other LMC WN9 stars, this object shows somewhat stronger profiles than S119 (see Fig. 13) but very a weak emission line spectrum (see Fig. 13 for profile fits). similar stellar parameters, except for a lower luminosity (Ta- − ◦ The derived stellar parameters for AB18 resemble Sk 69 249c ble 2). While our observations do show weak [N ii] λλ6548– from Paper I except for a lower luminosity (log (L/L )∼5.5), 6583 emission (Fig. 5), contamination of the stellar Balmer fea- . −1 and mass-loss rate (log (M/(M yr )) ∼−5.0). The absence tures is negligible so that the derived chemical composition of ultraviolet observations means that the reddening is poorly (H/He∼3) should be accurate. While we are unaware of ex- constrained, and thus a rigorous MV determination is not pos- isting K-band spectroscopy of S142, our model predicts He i sible. 2.058µm ≈ Brγ emission.

A.13. BE294 (HDE 269582, WN10h) A.16. S61 (BE153, WN11h) BE294 has previously been classified as Ofpe/WN9 (Bohannan Finally, S61 is another star revised to WN11h from Ofpe/WN9 & Walborn 1989) and identified as a LBV (Bohannan 1989), whose spectrum and physical parameters (Fig. 13) closely and is now re-classified as WN10h. The optical morphology mimic S119, except for marginally stronger He ii λ4686. The of this star closely resembles the other LMC WN10 star S9 nebula surrounding S61 contributes ≥75% of the Hα line flux (Sk−66◦ 40, Paper I). While the stellar temperature (∼29kK) (Sect. 3.3; Fig. 5). After nebular subtraction, we obtain a rel- and wind velocity (∼300 km s−1) of BE294 are almost identi- atively low hydrogen content of H/He∼1.2. Indeed, as for cal to S9 (Table 2), it is more luminous and exhibits a more Model A for S119, assuming that the Balmer line strengths re- chemically processed surface composition (H/He∼1.9). Mc- sult purely from stellar emission would imply a huge hydrogen Gregor et al. (1988) estimated H/He=0.5–2 for BE294 from its content (H/He∼6). McGregor et al. (1988) obtained K-band K-band spectrum. Profile fits for BE294 are shown in Fig. 13. spectroscopy of S61 showing He i 2.058µm and Brγ emission of Our present model slightly underestimates the observed emis- comparable strength, and estimated H/He∼5. In common with sion strength of He i 2.058µm relative to Brγ (Blum et al. 1995), other WN10–11 stars studied here the predicted He i 2.058µm as was previously found for S9 in Paper I. Incidentally, BE294 emission is somewhat weaker than that observed, which we at- showed significant variability in the IR He i/Brγ flux ratio be- tribute to the neglect of line blanketing (Paper I; Najarro et al. tween 1987 January and 1993 September, when McGregor et 1994). al. (1988) recorded ∼3 and Blum et al. (1995) obtained ∼0.3.

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Table 4. Journal of intermediate to high dispersion optical spectroscopic observations collected at the 3.9m Anglo- Australian Telescope (AAT), and the 1.9m telescope at Mount Stromlo Observatory (MSO)

Star Spectral Telescope Spectrograph Epoch Wavelength Exposure Spectral Type +Detector Range (A)˚ Time (s) Res. (A)˚ Brey 24 WN6h AAT RGO + 1K Tek CCD 5-6 Nov 1992 3670–6000 2 600 1.7 Brey 26 WN6(h) AAT RGO + 1K Tek CCD 2-6 Nov 1992 3670–6000 2 800 1.7 MSO coude+´ 2K Tek CCD 3 Dec 1995 5730–6730 1 800 1.0 Brey 47 WN6h AAT RGO + 1K Tek CCD 26 Dec 1994 3670–6000 5 100 1.7 Brey 75 WN6(h) MSO coude+´ 2K Tek CCD 2 Dec 1995 4010–6710 2 700 2.0 Brey 89 WN6h AAT RGO + 1K Tek CCD 2-4 Nov 1992 3670–6000 1 580 1.7 MSO coude+´ 2K Tek CCD 2 Dec 1995 4740–6710 600 2.0 Brey 90 WN6(h) AAT RGO + 1K Tek CCD 4-5 Nov 1992 3670–6000 4 050 1.7 MSO coude+´ 2K Tek CCD 2 Dec 1995 4740–6710 600 2.0 Brey 71 WN7h AAT RGO + 1K Tek CCD 26 Dec 1994 3670–6000 2 700 1.7 Brey 80 WN7h AAT RGO + 1K Tek CCD 25 Dec 1994 3670–6000 1 310 1.7 MSO coude+´ 2K Tek CCD 2 Dec 1995 4740–6710 1 500 2.0 Brey 13 WN8h AAT RGO + 1K Tek CCD 2-6 Nov 1992 3670–6000 4 570 1.7 MSO coude+´ 2K Tek CCD 2 Dec 1995 4740–6710 900 2.0 Brey 36 WN8h AAT RGO + 1K Tek CCD 3-6 Nov 1992 3670–6000 3 300 1.7 Brey 81 WN8(h) MSO coude+´ 2K Tek CCD 2 Dec 1995 4010–5980 1 800 2.0 AB18 WN9h AAT RGO + 1K Tek CCD 25 Dec 1994 3670–6000 3 000 1.7 R99 Of/WN AAT UCLES+ 1K Thomson CCD 27 Dec 1991 4070–5100 7 200 0.1 AAT RGO + 1K Tek CCD 25 Dec 1994 3670–6770 1 320 1.7 BE294 Of/WN AAT RGO + 1K Tek CCD 25 Dec 1994 3670–6000 1 230 1.7 MSO coude+´ 2K Tek CCD 2 Dec 1995 4740–6710 1 200 2.0 MSO coude+´ 2K Tek CCD 3 Dec 1995 5730–6730 1 200 1.0 S119 Of/WN AAT UCLES+ 1K Thomson CCD 27 Dec 1991 4070–5100 3 600 0.1 AAT RGO + 1K Tek CCD 25 Dec 1994 3670–6000 1 550 1.7 MSO coude+´ 2K Tek CCD 2 Dec 1995 4740–6710 900 2.0 MSO coude+´ 2K Tek CCD 3 Dec 1995 5730–6730 1 200 1.0 S142 Of/WN AAT RGO + 1K Tek CCD 25 Dec 1994 3670–6000 1 400 1.7 MSO coude+´ 2K Tek CCD 2 Dec 1995 4740–6710 1 500 2.0 MSO coude+´ 2K Tek CCD 3 Dec 1995 5730–6730 1 800 1.0 S61 Of/WN AAT RGO + 1K Tek CCD 25 Dec 1994 3670–6000 1 050 1.7 MSO coude+´ 2K Tek CCD 2 Dec 1995 4740–6710 1 200 2.0 MSO coude+´ 2K Tek CCD 3 Dec 1995 5730–6730 1 200 1.0 520 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI

Fig. 11. Synthetic profile fits (dotted lines) to radial velocity corrected observations of WN6 stars (solid line) for He ii λ4686, λ5412, Hγ–α, He i λ5876. Observations are AAT–RGO except where indicated. Spikes observed in profiles of Brey 75 are caused by the poor removal of the 30 Dor nebular component P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 521

Fig. 12. Synthetic profile fits (dotted lines) to radial velocity corrected observations of WN6–8 stars (solid line) for He ii λ4686, λ5412, Hγ–β, He i λ4471, λ5876. Observations are AAT–RGO except where indicated. Spikes and data gaps observed in profiles of Brey 80 and Brey 90 are caused by the poor removal of the 30 Dor nebular component 522 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI

Fig. 13. Synthetic profile fits (dotted lines) to radial velocity corrected observations of WN8–11 stars (solid line) for He ii λ4686, λ5412, Hγ–α, He i λ4471, λ5876. Observations are AAT–RGO except where indicated P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI 523

Table4. Journal of high dispersion UV (IUE–HIRES, HST–FOS) spec- troscopic observations

Star Spect. Telescope Epoch Exposure Type Instrument Time (s) Brey 24 WN6h IUE/SWP 8 Aug 1993 17 700 Brey 26 WN6(h) IUE/SWP 10 May 1992 23 400 Brey 89 WN6h IUE/SWP 14 Feb 1979 18 000 IUE/SWP 16 Apr 1979 19 935 Brey 90 WN6(h) IUE/SWP 8 Jun 1993 19 500 IUE/SWP 10 Jul 1993 21 000 Brey 13 WN8h IUE/SWP 12 May 1992 24 000 R99 Of/WN HST/FOS 21 Oct 1993 10 150 BE294 Of/WN HST/FOS 6 Sep 1993 3 090 S119 Of/WN HST/FOS 29 Sep 1993 2 750 S61 Of/WN HST/FOS 15 Oct 1993 2 300

Table 5. Wind velocities (in km s−1) measured from UV P Cygni res- onance lines in high dispersion spectra following Prinja et al. (1990), UV low dispersion spectra following Prinja (1994, given in paren- thesis) or optical He i P Cygni profiles. Previous determinations by Koesterke et al. (1991, KHSW) using optical He i profiles and Ro- chowicz & Niedzielski (1995, RN) using UV low dispersion spectra are also shown for comparison

Star Spect. KHSW Si iv C iv He i v∞ Type (RN) 1393.8 1402.8 1548.2 5875.7 Brey 24 WN6h 1200 940 900 940 Brey 26 WN6(h) 1600 1430 1400 (1500) 1520 1520 Brey 47 WN6h 900 890 890 Brey 75 WN6(h) 1290 1290 Brey 89 WN6h (1475) 1310 1290 1460 1100 1460 Brey 90 WN6(h) (1515) (1500) 1350 1350 Brey 71 WN7h (1195) 1000 1000 Brey 80 WN7h (1295) (1430) 1830 1830 Brey 13 WN8h 1000 890 850 860 850 Brey 36 WN8h (780) 670 670 Brey 81 WN8(h) 830 830 AB18 WN9h 490 490 BE294 WN10h 350 390 360 320 320 S119 WN11h 330 370 240 230 230 S142 WN11h 250 250 S61 WN11h 360 340 230 250 250

Fig. 14. Synthetic profile fits (dotted lines) to radial velocity corrected observations of S119 (solid lines). Model A fits are to observations (AAT–RGO, MSO–coude)´ including Balmer nebula contamination while Model B fits are to observations (AAT–UCLES, MSO–coude)´ excluding nebula contamination. Data are AAT–RGO except where indicated 524 P.A.Crowther & L.J. Smith: Fundamental parameters of Wolf-Rayet stars. VI

−1 Table 6. Selected optical emission equivalent widths (Wλ,inA),˚ FWHM (in A)˚ and radial velocities (in km s ) for the programme LMC WN6–11 stars based on our new AAT and MSO observations (∗ indicates Hα data from MSO). Measurements for WN9–10 stars from Paper I are also shown (including new Hα MSO observations). The Balmer line strengths for S119 and S61 include a strong nebular contribution

Star Spectral Observations FWHM Wλ Wλ Wλ Wλ Wλ Wλ Wλ Wλ Wλ Wλ Radial Type He ii He i N iv Hγ He i N iii He ii Hβ He ii He i Hα vel. λ4686 λ3889 λ4058 λ4472 λ4640 λ4686 λ5412 λ5876 km s−1 Brey 24 WN6h AAT–RGO 12.5 2.7 5.4 7.1 0.7 16.2 62.8 18.5 10.0 6.8 – 280 Brey 26 WN6(h) AAT–RGO∗ 19.5 1.6 7.3 5.5 0.5 8.5 93.4 16.2 16.3 8.7 64.1 150 Brey 47 WN6h AAT–RGO 11.4 2.5 3.8 5.7 0.4 15.5 47.6 15.5 8.6 7.3 – 250 Brey 75 WN6(h) MSO–coude´ 16.5 – 4.1 3.5 0.4 12.3 61.6 9.5 11.9 7.2 45.4 260 Brey 89 WN6h AAT–RGO∗ 17.8 1.9 4.3 5.5 0.6 8.2 75.0 15.9 11.0 6.5 68.9 240 Brey 90 WN6(h) AAT–RGO∗ 16.8 1.1 3.7 2.1 0.5 7.4 55.2 10.7 8.8 5.0 55.4 260 Brey 71 WN7h AAT–RGO 13.7 8.8 8.8 13.7 4.4 23.2 92.5 30.1 16.9 19.3 – 280 Brey 80 WN7h AAT–RGO∗ 18.9 13.8 5.4 13.0 6.7 18.0 89.7 25.9 17.7 29.2 86.6 260 Brey 13 WN8h AAT–RGO∗ 11.8 10.2 6.0 12.2 5.0 26.9 58.6 27.5 10.2 26.8 100.0 260 Brey 36 WN8h AAT–RGO 8.1 4.4 2.0 6.0 2.3 14.7 27.4 15.1 4.4 12.4 – 350 Brey 81 WN8(h) MSO–coude´ 11.2 – 1.4 3.1 4.7 18.4 45.3 10.6 8.8 18.4 – 240 R84 WN9h AAT–RGO∗ 4.6 7.5 0.0 8.6 3.3 5.9 4.9 21.0 0.4 15.8 54.2 260 AB18 WN9h AAT–RGO 5.1 1.2 0.0 0.9 0.7 3.4 7.6 3.4 0.7 4.7 – 260 BE381 WN9h AAT–RGO∗ 4.3 5.2 0.0 7.2 2.5 4.9 7.5 12.5 0.4 14.6 56.1 300 Sk-69 249c WN9h AAT–RGO∗ 4.8 3.1 0.0 5.6 1.6 3.3 6.4 9.7 0.6 11.7 45.2 270 S9 WN10h AAT–RGO∗ 3.8 7.4 0.0 4.1 3.5 3.7 2.7 26.5 0.1 20.0 107.1 280 BE294 WN10h AAT–RGO∗ 4.0 8.9 0.0 8.3 3.9 4.5 3.9 20.6 0.3 24.1 102.8 270 S119 WN11h AAT–RGO∗ 3.8 2.0 0.0 2.3 0.5 0.2 0.7 7.6 0.0 5.4 32.3 140 AAT–UCLES 1.6 – – 0.9 0.6 0.4 0.3 4.3 – – – 160 S142 WN11h AAT–RGO∗ 3.3 2.9 0.0 3.3 1.2 1.4 1.1 9.2 0.0 8.6 43.6 290 S61 WN11h AAT–RGO∗ 3.7 2.0 0.0 2.7 0.5 0.7 1.1 9.3 0.0 5.4 82.6 280

Table 7. Optical and IR photometry and absolute magnitudes of the programme LMC stars. Since narrow band b, v (Smith 1968) optical photometry is available for only a subset of our programme stars we utilise wide band B, V Johnson photometry (typically within 0.05 mag of narrow band measurements for WNL stars). Our derived EB−V determination, including a 0.05 mag Galactic component, is compared with the previous values from L.J. Smith & Willis (SW, 1983), Schmutz & Vacca (SV, 1991) and Morris et al. (PWM, 1993a)

SW SV PWM Star Sp.Type V B−VU−B Ref. J H K Ref. EB−V EB−V EB−V EB−V MV mag mag mag mag mag mag mag mag mag mag mag Brey 24 WN6h 13.36 −0.22 −0.98 1 13.24 13.25 13.07 3 0.05 0.04 0.05 0.06 −5.36 Brey 26 WN6(h) 12.71 −0.25 −0.95 1 12.66 12.59 12.35 3 0.05 0.04 0.09 0.05 −5.98 Brey 47 WN6h 14.99 +0.30 −0.53 1 0.53 0.50 −5.10 Brey 75 WN6(h) 12.63 +0.03 −0.54 7 0.25 −6.72 Brey 89 WN6h 11.10 −0.12 −0.87 7 10.91 10.76 10.54 3 0.10 0.15 0.08 0.10 −7.75 Brey 90 WN6(h) 12.04 −0.01 −0.79 7 11.33 11.12 10.86 3 0.30 0.32 0.22 0.30 −7.43 Brey 71 WN7h 14.19 +0.05 −0.65 2 0.25 −5.12 Brey 80 WN7h 13.07 −0.17 −0.35 7 0.23 −6.18 Brey 13 WN8h 12.71 −0.23 −0.93 1 12.35 12.29 12.04 3 0.05 0.07 0.03 0.08 −6.08 Brey 36 WN8h 13.46 −0.20 −0.93 1 0.09 0.08 0.09 −5.36 Brey 81 WN8(h) 13.65 +0.39 −0.42 7 0.60 −6.82 AB18 WN9h 14.23 +0.23 −0.73 4 0.57 −6.07 BE294 WN10h 11.88 −0.04 −0.91 5 11.51 11.44 11.17 9 0.09 −6.94 S119 WN11h 11.90 −0.07 −0.97 6 11.73 11.65 11.58 8 0.10 −6.95 S142 WN11h 12.73 +0.11 −0.78 6 12.20 12.10 11.81 9 0.26 −6.61 S61 WN11h 12.02 −0.09 −1.00 5 11.90 11.90 11.71 8 0.05 0.10 −6.84

(1) Feitzinger & Isserstedt (1983); (2) Schild & Testor (1992); (3) Hillier (private communication); (4) Azzopardi & Breysacher (1985); (5) Stahl (1986); (6) Isserstedt (1975); (7) Parker (1993); (8) McGregor et al. (1988); (9) Gummersbach et al. (1995)