| Issue |
A&A
Volume 570, October 2014
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|---|---|---|
| Article Number | A38 | |
| Number of page(s) | 92 | |
| Section | Stellar atmospheres | |
| DOI | https://doi.org/10.1051/0004-6361/201423643 | |
| Published online | 13 October 2014 | |
Online material
Appendix A: Comments on individual objects
Here we describe the individual properties of the Of/WN and WNh stars in our sample (Sect. A.1). This is followed by a discussion of two peculiarities that occurred during the spectroscopic analysis (Sect. A.2).
Appendix A.1: Of/WN, WNh and WN(h) stars
We now give a short summary of individual stars and their characteristics.
VFTS 108 (BAT99-089/Brey71): a single WN7h-star with no noticeable variation in the peak intensity of the emission lines between the observed epochs. There are no absorption lines suitable for RV measurements to investigate the presence of a companion or the stars’s runaway status. The star is not located in a cluster and lies in the field surrounded by a few fainter objects. The quality of the model is reasonably good and the derived stellar parameters are well constrained (Fig. E.6).
VFTS 147 (BAT99-091/Brey73): the star has the spectral type WN6(h) and is not a known binary or multiple component system. According to Schnurr et al. (2008) it does not show any variability. However, the star is located in the Brey 73 cluster with a bright object nearby. In several epochs absorption features from a possible OB star are visible in the VFTS spectra. The presence/absence of these features is due to slightly different offsets of the MEDUSA fibre position and/or variations in the atmospheric seeing. The mass-loss rate and temperature estimation are uncertain. The low spatial resolution of the available optical photometry unrealistically high flux in the B and V bands. The continuum estimated from the near-IR VISTA photometry is less affected (or unaffected), which results in a negative extinction parameter E(V − Ks). The estimated luminosity is therefore based on the Ks magnitude. photometry (Sect. 3.4), but The luminosity might be up to ~0.2 dex too high depending on the uncertainties in the near-IR photometry and the near-IR flux of the nearby star. The star is excluded from the discussion (Fig. E.8).
VFTS 402 (BAT99-095/Brey80): this WN7(h) star has a probable OB companion. Schnurr et al. (2008) classified it as binary system with a short orbital period of ≈2 days. The model fit quality is very poor as a result of the presence of the secondary. The temperature, mass-loss rate and helium abundance determinations are highly uncertain (Fig. E.18). The impact of the secondary on the total continuum is not known, which leads to an incorrect luminosity. The star is excluded from the discussion.
VFTS 427 (BAT99-096/Brey81): a single star with no noticeable change in the peak intensity of the emission lines between the observed epochs. The WN8(h)-star is surrounded by a few nearby fainter objects, which do not considerably influence the spectra or the continuum. There are no photospheric absorption lines to study RV variations due to any possible secondary. The quality of the model is good and the derived stellar parameters are reasonably accurate (Fig. E.22).
VFTS 457 (BAT99-097): the star is classified as O3.5if*/WN7 and is not a known binary. Small LPVs are observed in the spectra which might be a result of the normalisation process. The fit to the nitrogen lines is poor, in particular for N iii. However, test calculations show that an increase of the nitrogen abundance, moving the starting point of clumping closer to the stellar surface to a wind velocity of 10 km s-1, and a higher value of the wind parameter β improved the fit quality, but does not fundamentally change the result (see Figs. E.26 and E.27). These different properties might be a result of an extended or asymmetric atmosphere, as a result of rotation. The terminal velocity is between 900 and 1100 km s-1 lower than the other Of/WN stars. Nevertheless, the derived stellar properties are robust.
VFTS 482 (BAT99-099/Brey78/Mk39): VFTS 482 is classified as O2.5if*/WN6. Massey et al. (2002) identified spectral variability while Massey et al. (2005) detected a composite in the spectra, but provided no classification of the secondary. According to Schnurr et al. (2008) it is a elliptical system with a period of 92.6 days (close to their detection limit). The quality of the fit is good. The temperature, mass-loss rate and He-abundance can be well determined (Fig E.29). The star is located in a relatively crowded field. The luminosity might be over estimated because of its unclear binary nature.
VFTS 509 (BAT99-103/Brey87): this WN5(h) star is part of a binary system with a separated early O star companion (Evans et al. 2011; Doran et al. 2013). Schnurr et al. (2008) give a period of 2.76 days. The fit quality is poor, but gives a fair hint of the actual stellar parameters (Fig. E.31). Still, the star is excluded from the discussion.
VFTS 542 (BAT99-113): this O2if*/WN5 star is a binary system with a period of 4.7 days (Schnurr et al. 2008). It is located in a crowded field. The quality of the model fit is good. The temperature, mass-loss and helium abundance can be determined (Fig. E.37). The luminosity is uncertain, because it is unclear how the continuum is affected by the secondary.
VFTS 545 (BAT99-114): as reported by Hénault-Brunet et al. (2012) there are weak RV variations in the spectra of this O2if*/WN5 star. There is no contamination of the stellar spectra; the fit is good and the results are robust (Fig. E.38).
VFTS 617 (BAT99-117/Brey88): this single star is classified as a WN5ha. The spectra show LPVs particularly in the Balmer series. The quality of the model is good. Ṁ varies as a result of the LPVs, but only within the error bars. (Fig. E.44).
VFTS 682: the WN5h-star is a newly discovered WR-star by the VFTS (Evans et al. 2011; Bestenlehner et al. 2011). The star appears to be single. The model fit is good and the results based on the grid are comparable with the parameters derived from Bestenlehner et al. (2011). The grid fit is shown in Fig. E.50.
VFTS 695 (BAT99-119/Brey90): this is a WR-star with spectral type of WN6h plus a companion. The binary system has a period of 158.8d (Schnurr et al. 2008). The spectra show LPVs in the Balmer series, in particular for Hα. The observations can be reasonably well reproduced by our model, however L⋆ might be over estimated (Fig. E.51).
VFTS 758 (BAT99-122/Brey91): this is a single WN5h-star. No noticeable line-profile and RV variations were found in the spectra. The fit quality regarding the grid resolution is good and the results are reasonably good (Fig. E.53).
VFTS 1001 (BAT99-100/Brey75): the WN6(h)-star is not a known binary. Hénault-Brunet et al. (2012) found possible LPVs in the He ii λ4542 line. The star is associated with an X-ray source. Portegies Zwart et al. (2002) suggested that these X-rays are potentially due to a wind-wind collision in a binary system. However, our model fits the observation well and we treat the object as if it is a single star (Fig. E.55).
VFTS 1017 (BAT99-104/Brey76): the O2 if*/WN5 spectra of this star show LPVs and weak RV variations (Hénault-Brunet et al. 2012). The possible companion does not impact the fit quality. The results are reliable with slightly larger uncertainties than most well fit stars in this study (Fig. E.57).
VFTS 1022: this star has been reclassified from O4 If+ (Massey & Hunter 1998) to O3.5 if*/WN7 by Crowther & Walborn (2011). The star shows small RV variations. Even though it is likely a binary, the derived stellar parameter are treated as if it were a single star (Fig. E.60).
VFTS 1025 (BAT99-112/Brey82/R136c): this WN5h-star is located in a crowded field and surrounded by multiple sources in HST observations by Massey & Hunter (1998). In their catalogue VFTS 1025 is designated as source No. 10 with MV = −6.8. One neighbouring HST source at an angular distance ≲0.5 arcsec is bright enough to affect our optical spectrum directly (source No. 57 with MV = −5.5, classified as O3 III(f*)). Furthermore the bright O star R136b (source No. 9, MV = −6.9, O4 If+) is relatively close at an angular distance of ≈1.3 arcsec. VFTS 1025 itself shows indications of binarity based on its strong X-ray emission (Guerrero & Chu 2008) and possible low-amplitude RV variations (Schnurr et al. 2009).
In our analysis we determine a significantly lower temperature than Crowther et al. (2010), mainly based on the He iλ4471 Å absorption line in the optical range. Our cooler temperature is further supported by the low terminal wind speed of VFTS 1025 compared to the other WN5(h) stars in R 136 analysed by Crowther et al. Their hotter temperature is based on the N v λ2.10 μm emission line in the IR. It is not clear if the He i line in our optical spectrum is intrinsic to VFTS 1025 or originates from a nearby star. We can exclude star No. 57 from Massey & Hunter as the origin of the He i line, based on the non-detection of strong enough He i in its HST spectrum. R136b has a weak He i absorption line and could possibly affect our spectrum. Hénault-Brunet et al. (2012) found LPVs for the prominent H and He ii emission lines but not for the He i absorption line in the spectrum of VFTS 1025. This is in line with a photospheric nature of the absorption line and wind variability in the emission lines as expected from our cool model, but also with a contribution from a nearby star.
Appendix A.2: Peculiarities
In this section we discuss three peculiarities that arose during our spectroscopic analysis. These peculiarities occurred as discrepancies between the observations and the model predictions. The plots of the model fits are shown in Appendix E.
Firstly, our models predict the C iii lines at λ4647/4650 Å in emission. Martins & Hillier (2012) discussed that these lines may appear in absorption or emission, depending on the detailed model assumptions. In our observations they appear in absorption for VFTS 171, 333, 532, and 669 and in emission for VFTS 216, 404, 422, 603, 608, and 797. Furthermore, VFTS 532 has a cooler companion that could contribute to the C iii absorption. In our analysis these lines are ignored.
Secondly, VFTS 208, 406, and 626 show He ii λ4686 Å emission profiles with a central absorption, which are characteristic for the fast rotating stars in the Onfp sub-class (see Walborn et al. 2010). This type of line profile has been modelled in 2D by Hillier et al. (2012). VFTS 406 has been classified as OVnn by Walborn et al. (2014) who find that its composite spectrum in the VFTS data is likely due to contamination by an adjacent WN spectrum on the detector. For VFTS 208 and 406 we only achieve a bad fit quality and the stars are excluded from our discussion.
Thirdly, for VFTS 259, 457, and 1021 the observed N iii λ4634/4640 Å lines are significantly stronger than in our theoretical models. Furthermore, there is a discrepancy between the diagnostic He i λ4471 Å line, and the N iii λ4634/4640 Å and N iv λ4058 Å lines for the effective temperature. To estimate the uncertainties we carried out test calculations for the O star 259 and Of/WN star 457. We found that the discrepancies can be significantly improved by simultaneously lowering log g by 0.5 dex, increasing the N-abundance by a factor 2, and moving the starting point of clumping closer to the surface (see Figs. E.26 and E.27 for the case of VFTS 457). The resulting parameters agree with those given in Table 3 within the given uncertainties.
Appendix B: Additional tables
Sources of spectroscopic data, line profile variation (LPV), and comments about binarity/multiplicity.
Aliases.
Adopted atomic model for the grid calculation.
The eight different abundances of our main grid given in mass fraction.
Appendix C: Temperature sensitivity and He-abundance
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Fig. C.1
Change of the line strengths of the helium and hydrogen emission lines with increasing temperature but constant luminosity and mass-loss rate. He ii shows a strong sensitivity at certain temperatures. The near-IR is more homogeneous, but slightly clumping dependent. For reasons of clarity the relative near-IR flux (F) is scaled to the power 3 (F3). |
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Fig. C.2
Change of the ratio of the helium and hydrogen emission lines with increasing helium abundance. The mass-loss rate of the models is 10-5M⊙ yr-1 and the temperature is ~ 50 000 K. For reasons of clarity, the relative near-IR flux (F) is scaled to the power 3 (F3). |
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Appendix D: The influence of log g on the stellar parameters
A variation of log g changes the density and ionisation balance in the stellar atmosphere. This can directly affect the derived temperature and helium abundance and with it the luminosity and the mass-loss rate. Here, we investigate the effect of varying surface gravity on the result for the O-type stars. For this purpose, we used our log g sub-grid with some additional smaller steps in helium abundance, and analysed a small sub-sample of O stars in that parameter space. More accurate parameters using a different stellar atmosphere code including a variable log g in the analysis will be provided by Ramirez-Agudelo et al. (in prep.) and Sabín-Sanjulián et al. (in prep.).
As shown in Figs. D.1 and D.2 a lower value of the surface gravity (Δlog g = 0.5 dex) requires a lower model temperature (ΔTeff = −0.025... − 0.03 dex) to match the main O star temperature diagnostic Hei λ4471. The transformed mass-loss rate is almost unchanged, within the given error bars. The lower Teff results in a lower luminosity (~ − 0.1 dex) and lower stellar mass. This gives a lower terminal velocity for the O stars using the relation by Lamers et al. (1995). These changes affect the mass-loss rates derived from Eq. (1) by about ~0.15 dex. The derived He-abundance decreases by 2...4%. The differences are larger for increasing temperature.
A variation of log g to values as low as 3.5 is only possible for the lowest Teff in our model grid. The reason is that for the hotter models the radiative flux (
) in the photosphere becomes so high that log grad exceeds 3.5, leading to a situation where Γ > 1 (cf. Eq. (3)) and no hydrostatic solution is possible. As Γ is generally high for the hotter models, and the spectroscopically relevant quantity is geff = g(1 − Γ), the log g needed to match the Hβ − δ line profiles of hot supergiants are not significantly lower than the log g of 4.0 adopted in our grid models. E.g., Evans et al. (2010) determined log g = 3.75 for VFTS 016 (O2 III-If*) in agreement with our own test computations.
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Fig. D.1
Left: the blue model has a lower log g of 0.5 dex compare to the red. Right: the temperature of the blue model is lower by 0.025 dex so that the line strength of the temperature diagnostic He i λ4471 matches the red model again. The differences in luminosity are around 0.1 dex, but the transformed mass-loss rate is unchanged. |
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Fig. D.2
Similar to Fig D.1, but at slightly higher temperature. He ii λ4686 increases significantly after lowering log g. The line strength is preserved after adjusting the temperature again. |
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Appendix E: Spectral modelling for each target star
In the appendix we show model fits for all our targets and describe how we obtained the stellar parameters. The first panel in the figures is the model SED (red solid line) fit to the optical and near-IR photometry (blue boxes). The reddening law and the RV is given in the bottom left corner. The following panels show the fits of the model spectra (red solid line) to the observations (blue solid line).
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Fig. E.1
VFTS 016 (O2 III-If*) is a known runaway (Evans et al. 2010). The temperature is based on the lines N iv λ4058, N v λ4604/4620, and on the absence of He i λ4471. Ṁ is based on the line shape of He ii λ4686. The blue wing of He ii λ4686 and the red wing of Hα is not properly reproduced by the model. However, the stellar parameters are in agreement with Evans et al. (2010). |
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Fig. E.2
VFTS 063 (O5 III(n)(fc)+ sec): the He i λ4471 line is a bit too broad possibly as a result of the star being a SB2. The N iii λ4634/4640 lines are a bit too weak whilst the C iii λ4647/4650 lines are too strong. N-abundance is between normal and enriched. |
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Fig. E.3
The temperature of VFTS 064 (O7.5 II(f)) is based on the He i λ4471 and N iii λ4634/4640 lines. Ṁ is based on the shape of the He ii λ4686 line. Nitrogen is enriched. |
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Fig. E.4
The temperature of VFTS 072 (O2 V-III(n)((f*))) is based on the lines N iii λ4634/4640, N iv λ4058, N v λ4604/4620, and on the absence of the He i λ4471 line. Ṁ is based on the line shape of He ii λ4686. Similar to Fig. E.1 the blue wing of He ii λ4686 and the red wing of Hα are not properly reproduced by the model. The star is nitrogen enriched and fast rotating. |
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Fig. E.5
He i λ4471 is too broad for VFTS 094 (O3.5 Inf*p + sec) possibly as a result of its status as a SB2. The fit quality is reasonably good for a SB2, but the luminosity is uncertain as the contribution of the secondary is unknown. N and He are enriched at the surface. The star is evolved with Hα and He ii λ4686 in emission. |
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Fig. E.6
The temperature of VFTS 108 (WN7h) is based on the lines He i λ4471, N iii λ4634/4640, N iv λ4058, N v λ4604/4620. The He mass fraction of the star is slightly lower than that in the 77.5% model. The N iv λ4058 and Hδ lines do not fit because of the normalisation. Even though the star is still relatively H-rich its position in the HRD suggests that the star is He-burning. Because of convergence difficulties the model had to be calculated with a lower log g. For emission lines log g does not affect the results. |
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Fig. E.7
The temperature of VFTS 145 (O8fp) is based on the lines He i λ4471, N iii λ4634/4640, and N iv λ4058. The He ii absorption lines are narrower than the models which suggests a lower log g value than 4.0. The spectrum shows weak RV variations and LPVs. The star is multiple in the HST observations and therefore the luminosity might be overestimated. N is enriched. He ii λ4686 is quite strong relative to Hα. The only way to increase the He ii emission line strength without increasing Ṁ is by increasing the He surface abundance. |
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Fig. E.8
The temperature of VFTS 147 (WN6(h)) is based on the lines He i λ4471, N iii λ4634/4640, N iv λ4058, N v λ4604/4620. The spectrum is contaminated by multiple nearby stars so as a result the obtained parameters are unreliable. The photometry is uncertain, too. Because of convergence difficulties the model has to be calculated with a lower log g. For emission lines log g does not affect the results. |
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Fig. E.9
The temperature of VFTS 151 (O6.5 II(f)p) is based on the lines He i λ4471, N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. The He ii absorption lines are slightly narrower than the models which suggests a log g value below 4.0. The spectrum shows weak RV variations and LPVs. The star is multiple in the HST observations and the luminosity might be overestimated. N is enriched. He ii λ4686 is in emission whilst Hα is in absorption which suggests He enrichment at the surface. |
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Fig. E.10
The temperature of VFTS 169 (O2.5 V(n)((f*))) is based on the lines He i λ4471, N iv λ4058, and N v λ4604/4620. Ṁ is based on He ii λ4686. The stellar rotation is high and the model spectrum is convolved with a rotation profile. N-abundance is normal. |
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Fig. E.11
The temperature of VFTS 171 (O8 II-III(f)) is based on the lines He i λ4471 and N iii λ4634/4640. Ṁ is based on the line shape of He ii λ4686, but Ṁ of the best fitting model is a bit high. We note that C iii λ4647/4650 is in emission in the models, but in absorption in the observations (Appendix A.2). N-abundance is between normal and enriched. |
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Fig. E.12
The temperature of VFTS 180 (O3 If*) is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. He i λ4471 is too strong in absorption, but it can be resolved by lowering log g which is suggested by the width of Hγ and Hδ. Ṁ is based on He ii λ4686 and Hα and is slightly too high for the best fitting model. |
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Fig. E.13
The temperature of VFTS 208 (O6(n)fp) is based on the absence of the N iv λ4058 line. The line wings of the observations are narrower and He i λ4471 is too strong, which suggests a significantly lower log g. The star is a fast rotator and the spectrum is peculiar (Appendix A.2). |
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Fig. E.14
The temperature of VFTS 216 (O4 V((fc))) is based on the lines He i λ4471 and N iv λ4058. Ṁ is based on the line shape of He ii λ4686. N is not enriched at the surface. |
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Fig. E.15
The temperature of VFTS 259 (O6 Iaf) is based on the absence of the N iv λ4058 line. The line wings of the observations are narrower and He i λ4471 is too strong, which suggests a lower log g ≈ 3.5. Nitrogen is enriched, but N iii λ4634/4640 can only be reproduced by increasing the abundance additionally by a factor of two. C iii λ4647/4650 are present in the spectrum. Test models show that a reduction of log g, enhancing N, and moving the starting point of clumping closer to the surface, improves the fit quality, but only slightly change the derived parameters. |
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Fig. E.16
The temperature of VFTS 267 (O3 III-I(n)f*) is based on the lines He i λ4471 and N iv λ4058. Ṁ is based on the line shape of He ii λ4686. N-abundance is between normal and enriched. |
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Fig. E.17
The temperature of VFTS 333 (O8 II-III((f))) is based on the lines He i λ4471 and N iii λ4634/4640. Ṁ is based on the line shape of He ii λ4686. We note that C iii λ4647/4650 is in emission in the models, but in absorption in the observations (Appendix A.2). N is not enriched at the surface. |
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Fig. E.18
The spectrum of VFTS 402 (WN7(h) + OB) shows the characteristic of a SB2. The temperature is based on the lines He i λ4471, N iii λ4634/4640, and N iv λ4058. Ṁ is based on He ii λ4686 and Hα. The fit quality is very poor as result of the secondary. The He mass fraction is between 85.0 and 92.5%. The optical photometry is contaminated by nearby stars which results in an unusually low RV = 0.85. |
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Fig. E.19
The spectrum of VFTS 404 (O3.5 V(n)((fc))) shows the characteristic of a SB1. The temperature is based on the lines He i λ4471, N iii λ4634/4640, and N iv λ4058. Ṁ is based on the line shape of He ii λ4686. N-abundance is normal. |
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Fig. E.20
The temperature of VFTS 406 (O6 nn(f)p) is based on the absence of the N iv λ4058 line. The line wings of the observations are narrower, which suggests a lower log g. The star is a fast rotator and the spectrum is peculiar (Appendix A.2). Nitrogen is enriched. |
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Fig. E.21
The spectrum of VFTS 422 (O4 III(f)) shows the characteristic of a SB1. The temperature is based on the lines N iii λ4634/4640 and N iv λ4058. The He i λ4471 line could not be used due to the strong nebular contamination. Ṁ is based on the line shape of He ii λ4686 and is a bit too high in the model. N-abundance is between normal and enriched. |
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Fig. E.22
The temperature of VFTS 427 (WN8(h)) is based on the lines He i λ4471, N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. Ṁ and He abundance are based on He ii λ4686, Hα. The fit quality is reasonably good for a late WNh star. |
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Fig. E.23
The spectrum of VFTS 440 (O6-6.5 II(f)) might be a SB1 or SB2. The temperature is based on the lines He i λ4471 and N iii λ4634/4640. Ṁ is based on the line shape of He ii λ4686 and is slightly too low in the model. Nitrogen is enriched at the stellar surface. |
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Fig. E.24
The spectrum of VFTS 445 (O3-4 V:((fc)): + O4-7 V:((fc)):) shows the characteristic of a SB2. The temperature is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. He i λ4471 could not be used due to the strong nebular contamination. Ṁ is based on the line shape of He ii λ4686. N-abundance is between normal and enriched. |
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Fig. E.25
The spectrum of VFTS 455 (O5: V:n) shows the characteristic of a SB1. The temperature is based on the lines He i λ4471 and N iv λ4058. Ṁ is based on the line shape of He ii λ4686. The star is a fast rotator. N-abundance is between normal and enriched. |
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Fig. E.26
The temperature of VFTS 457 (O3.5 If*/WN7) is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. Ṁ is based on He ii λ4686 and Hα. The best fitting model Ṁ is slightly too high. The star suggests an unusually high N abundance. The quality of the fit is not good, but can be easily improved (see Fig. E.27). |
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Fig. E.27
Improved test model for VFTS 457 (O3.5 If*/WN7) relative to Fig. E.26. The N abundance is twice that of our enriched models. In addition, the model differs by having a lower log g (3.5 dex) and by starting the clumping in the wind velocity law at 10 km s-1. Ṁ was reduced as well to compensate the line strength increases as a result of the lower log g. The difference in Ṁ is less than 0.1 dex. |
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Fig. E.28
VFTS 468 (O2 V((f*)) + OB) has stars nearby, is multiple in HST images, and has a composite spectrum. The temperature is based on the lines He i λ4471, N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. Ṁ is based on the line shape of He ii λ4686. N is enriched. |
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Fig. E.29
VFTS 482 (O2.5 If*/WN6) is surrounded by nearby stars, which could have an impact on the spectroscopy and photometry. The temperature is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. Ṁ and He-abundance are based on the lines He ii λ4686, Hα, He ii 2.19 μm, and |
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Fig. E.30
The temperature of VFTS 506 (ON2 V((n))((f*))) is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. The model temperature is slightly too low. Ṁ is based on the line shape of He ii λ4686. log g might be a bit higher, because the observations are a bit broader than the model. The star is fast rotating. N-abundance is between normal and enriched. |
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Fig. E.31
The spectrum of VFTS 509 (WN5(h) + early O) shows the characteristic of a SB2. The temperature is based on the lines N iii λ4634/4640, and N iv λ4058. Ṁ and He-abundance are based on He ii λ4686 and Hα. The fit quality is poor as result of the secondary. |
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Fig. E.32
The spectrum of VFTS 512 (O2 V-III((f*))) shows the characteristic of a SB1. The temperature is based on the lines He i λ4471, N iv λ4058, and N v λ4604/4620. Ṁ is based on the line shape of He ii λ4686. N-abundance is between normal and enriched. |
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Fig. E.33
The temperature of VFTS 518 (O3.5 III(f*)) is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. Ṁ is based on the line shape of He ii λ4686. C is reduced and N is enriched. |
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Fig. E.34
The spectrum of VFTS 527 (O6.5 Iafc + O6 Iaf) shows the characteristic of a SB2. The temperature and mass-loss rate are difficult to determine. We tried to fit the spectrum with a single model from our grid. The line width of the absorption lines suggests a lower log g. The fit quality is poor as result of the SB2 characteristic and the derived Teff, Ṁ and the luminosity are quite uncertain. No He enrichment at the stellar surface. Combining two single star models would improve the fit quality. |
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Fig. E.35
The temperature of VFTS 532 (O3 V(n)((f*))z + OB) is based on the lines He i λ4471 and N iv λ4058. Ṁ is based on the line shape of He ii λ4686. We note that C iii λ4647/4650 is in emission in the models, but in absorption in the observations (Appendix A.2). N is not enriched at the surface. The star is fast rotating. |
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Fig. E.36
The spectrum of VFTS 538 (ON9 Ia + O7.5 Ia(f)) shows the characteristic of a SB2. The temperature is based on the He i λ4471 line. Ṁ is roughly based on the line shape of He ii λ4686. The line width of the absorption lines suggests a lower log g. The fit quality is rather poor and Teff and Ṁ are quite uncertain. |
| Open with DEXTER | |
 |
Fig. E.37
VFTS 542 (O2 If*/WN5): the second (ARGUS) and third (MEDUSA) panel cover the same wavelength range and the spectra are similar (except for the degree of the nebular contamination). The temperature is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. Ṁ and He-abundance are based on the lines He ii λ4686, Hα, He ii 2.19 μm, and |
| Open with DEXTER | |
 |
Fig. E.38
The temperature of VFTS 545 (O2 If*/WN5) is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. Ṁ and He-abundance are based on He ii λ4686, Hα, He ii 2.19 μm, and |
| Open with DEXTER | |
 |
Fig. E.39
VFTS 562 (O4V): Hα is not observed. Hence, the He abundance is uncertain. The temperature is based on the lines He i λ4471, N iii λ4634/4640, and N v λ4604/4620. Ṁ is based on the line shape of He ii λ4686. The line width of the absorption lines suggests a lower log g. The presence of C suggests a He-abundance of 25% at the surface. |
| Open with DEXTER | |
 |
Fig. E.40
The temperature of VFTS 566 (O3 III(f*)) is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. Ṁ is based on the line shape of He ii λ4686. N is enriched. |
| Open with DEXTER | |
 |
Fig. E.41
The temperature of VFTS 599 (O3 III(f*)) is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. Ṁ is based on the line shape of He ii λ4686. N is enriched. |
| Open with DEXTER | |
 |
Fig. E.42
The spectrum of VFTS 603 (O4 III(fc)) shows the characteristic of a SB1. The temperature is based on the lines N iii λ4634/4640 and N iv λ4058. He i λ4471 is contaminated by nebular emission and is not used. Ṁ is based on the line shape of He ii λ4686. N-abundance is between normal and enriched. |
| Open with DEXTER | |
 |
Fig. E.43
The spectrum of VFTS 608 (O4 III(f)) shows the characteristic of a SB1. The temperature is based on the lines N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. He i λ4471 is contaminated by nebular emission and is not used. Ṁ is based on the line shape of He ii λ4686. Nitrogen is enriched. |
| Open with DEXTER | |
 |
Fig. E.44
The temperature of VFTS 617 (WN5ha) is based on the lines N iv λ4058, N v λ4604/4620, and N v λ4945. Ṁ and He-abundance are based on He ii λ4686 and Hα. |
| Open with DEXTER | |
 |
Fig. E.45
The temperature of VFTS 621 (O2 V((f*))z) is based on N iii λ4634/4640, N iv λ4058, and N v λ4604/4620. Ṁ is estimated using the line shape of He ii λ4686 and is uncertain. N is enriched. |
| Open with DEXTER | |
 |
Fig. E.46
The line profiles of VFTS 626 (O5-6 n(f)p) are broadened as a result of rotation. The temperature is based on the lines He i λ4471 and N iii λ4634/4640. Ṁ is based on the line shape of He ii λ4686 and Hα. The best fit has a He-abundance of 40%. N is enriched. |
| Open with DEXTER | |
 |
Fig. E.47
The temperature of VFTS 664 (O7 II(f)) is based on He i λ4471 and N iii λ4634/4640. Ṁ is based on the line shape of He ii λ4686. N is enriched. |
| Open with DEXTER | |
 |
Fig. E.48
The temperature of VFTS 669 (O8 Ib(f)) is based on the lines He i λ4471 and N iii λ4634/4640. Ṁ is based on the line shape of He ii λ4686. N is enriched and He might be as well. The absorption lines are narrower than the model, which suggests a lower log g. By lowering log g N iii λ4634/4640 would be stronger in emission and improve the fit (Fig. E.49). |
| Open with DEXTER | |
 |
Fig. E.49
Test model for VFTS 669 (O8 Ib(f)) to investigate the predicted changes in temperature, luminosity and mass loss (see Figs. D.1 and D.2). As predicted the transformed mass-loss rate is still the same while the temperature (−0.025 dex) and the luminosity (−0.08 dex) are lower. |
| Open with DEXTER | |
 |
Fig. E.50
The temperature of VFTS 682 (WN5h) is based on the lines N iv λ4058, N v λ4604/4620, and on the absence of the He i λ4471 line. Ṁ and He-abundance are based on He ii λ4686 and Hα. The fit quality is reasonably good for a WNh stars. Even though the best fitting grid model has a slightly too high Ṁ. The results are similar to those from Bestenlehner et al. (2011). |
| Open with DEXTER | |
 |
Fig. E.51
The spectrum of VFTS 695 (WN6h + ?) shows the characteristic of a SB1. The temperature is based on the lines He i λ4471, N iii λ4634/4640, and N iv λ4058. Ṁ and He-abundance are based on He ii λ4686 and Hα. The He-abundance is between 85.0 and 92.5%. |
| Open with DEXTER | |
 |
Fig. E.52
The temperature of VFTS 755 (O3 Vn((f*))) is based on the lines He i λ4471 and N iv λ4058. Ṁ is based on the line shape of He ii λ4686. N-abundance is normal. |
| Open with DEXTER | |
 |
Fig. E.53
The temperature of VFTS 758 (WN5h) is based on the lines N iv λ4058, N v λ4604/4620, and on the absence of the He i λ4471 line. Ṁ and He-abundance are based on He ii λ4686 and Hα. The fit quality is reasonably good for a WNh stars, although Hδ could not be properly reproduced. |
| Open with DEXTER | |
 |
Fig. E.54
The temperature of VFTS 797 (O3.5 V((n))((fc))) is based on the lines He i λ4471 and N iv λ4058. Ṁ is based on the line shape of He ii λ4686. N is not enriched at the stellar surface. |
| Open with DEXTER | |
 |
Fig. E.55
VFTS 1001 (WN6(h)): The temperature is based on the lines He i λ4471, N iii λ4634/4640, N iv λ4058, N v λ4604/4620. Ṁ and He-abundance are based on the lines He ii λ4686, Hα, He ii 2.19 μm, and |
| Open with DEXTER | |
 |
Fig. E.56
The temperature of VFTS 1014 (O3 V + mid/late O) is based on the lines N iv λ4058, N v λ4604/4620, and on the He i λ4471 line. Unfortunately, the resolution and S/N of the HST observation is very low and Ṁ is based on N iv λ4058 instead of He ii λ4686. The log g is at least ≳4 and the luminosity class is V, which suggests a young age and a He-abundance of ≈25%. (Second panel: HST/FOS, third panel: ARGUS). |
| Open with DEXTER | |
 |
Fig. E.57
The temperature of VFTS 1017 (O2 If*/WN5) is based on the lines N iv λ4058, N v λ4604/4620, and He i λ4471. Ṁ and He-abundance are based on the lines He ii λ4686, Hα, He ii 2.19 μm, and |
| Open with DEXTER | |
 |
Fig. E.58
The temperature of VFTS 1018 (O3 III(f*) + mid/late O) is based on the lines N iii λ4634/4640, N iv λ4058, and He i λ4471. Unfortunately, the resolution and S/N of the HST observation is very low and Ṁ is based on the lines N iv λ4058, He ii 2.19 μm, and |
| Open with DEXTER | |
 |
Fig. E.59
The temperature of VFTS 1021 (O4 If+) is based on the lines N iii λ4634/4640 and N iv λ4058, and He i λ4471. Ṁ and He-abundance are based on He ii 2.19 μm and |
| Open with DEXTER | |
 |
Fig. E.60
The temperature of VFTS 1022 (O3.5 If*/WN7) is based on the lines N iii λ4634/4640, N iv λ4058, and He i λ4471. Ṁ and He-abundance are based on the lines He ii λ4686, He ii 2.19 μm, and |
| Open with DEXTER | |
 |
Fig. E.61
The temperature of VFTS 1025 (WN5h) is based on the lines N iii λ4634/4640 N iv λ4058, N v λ4604/4620, and He i λ4471. Ṁ and He-abundance are based on the lines He ii λ4686, He ii 2.19 μm, and |
| Open with DEXTER | |
 |
Fig. E.62
The temperature of VFTS 1026 (O3 III(f*) + mid/late O) is based on the lines N iv λ4058 and He i λ4471. Ṁ is estimated on the basis of the strength of the N iv λ4058 line and is highly uncertain. N is enriched. (Second panel: HST/FOS, third panel: ARGUS). |
| Open with DEXTER | |
 |
Fig. E.63
The temperature of VFTS 1028 (O3 III(f*) or O4-5V) is based on the lines N iv λ4058 and He i λ4471. Ṁ is estimated on the basis of the strength of the N iv λ4058 line and is highly uncertain. N is enriched. (Second panel: HST/FOS, third panel: ARGUS). |
| Open with DEXTER | |
 |
Fig. E.64
The temperature of Mk42 (O2 If*) is based on the lines N iii λ4634/4640 N iv λ4058, N v λ4604/4620, and He i λ4471. Ṁ and He-abundance are based on the lines He ii λ4686, Hα, He ii 2.19 μm, and |
| Open with DEXTER | |
© ESO, 2014
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