On the Mass-Loss Rate of Massive Stars in the Low-Metallicity Galaxies Ic 1613, Wlm, and NGC 3109

Tramper, F.; Sana, H.; Koter, A. de; Kaper, L.

doi:10.1088/2041-8205/741/1/l8

Cited by 53 publications

(126 citation statements)

References 45 publications

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“…As a result, the MWM rate of this star was much higher than predicted by the Vink et al (2001) relationship for its luminosity and metallicity (note that if the star is contaminated by a companion, which is always a worry at far distances, the actual luminosity would be lower and thus the discrepancy with the theory larger). As indicated in the introduction, this result is similar to that found by Tramper et al (2011) for stars in IC 1613, WLM and NGC 3109, who also adopted β (with values from 0.80 to 0.95, depending on luminosity class). As surprising as the β value obtained in this work may look, it solves the problem of the high MWM of GHV-62024, because it reduces the mass-loss rate while keeping all other parameters (nearly) fixed.…”

Section: The Wind Momentum Of Ghv-62024supporting

confidence: 87%

“…A preliminary analysis of this star by Herrero et al (2011) resulted in a too high log D mom as expected from its metallicity and luminosity, which would challenge the theory of radiatively driven winds at low metallicities. An even more serious challenge is the very recent work by Tramper et al (2011). These authors analysed six O-stars in low-Z galaxies (four in IC 1613 and one in WLM and NGC 3109).…”

Section: Introductionmentioning

confidence: 99%

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A peculiar Of star in the Local Group galaxy IC 1613

Herrero¹,

García²,

Puls³

et al. 2012

A&A

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Context.Results from the theory of radiatively driven winds are nowadays incorporated in stellar evolutionary and population synthesis models, and are used in our interpretation of the observations of the deep Universe. Yet, the theory has been confirmed only until Small Magellanic Cloud metallicities. Observations and analyses of O-stars at lower metallicities are difficult, but much needed to prove the theory. Aims. We have observed GHV-62024, an O6.5 IIIf star in the low-metallicity galaxy IC 1613 (Z ≈ 0.15 Z ) to study its evolution and wind. According to a previous preliminary analysis that was subject to significant restrictions this star could challenge the radiatively driven wind theory at low metallicities. Here we present a complete analysis of this star. Methods. Our observations were obtained with VIMOS at VLT, at R ≈ 2000 and covered approximately between 4000 and 7000 Å. The observations were analysed using the latest version of the model atmosphere code FASTWIND, which includes the possibility of calculating the N iii spectrum. Results. We obtain the stellar parameters and conclude that the star follows the average wind momentum-luminosity relationship (WLR) expected for its metallicity, but with a high value for the exponent of the wind velocity law, β. Comparing this with values of other stars in the literature, we suggest that this high value may be reached because GHV-62024 could be a fast rotator seen at a low inclination angle. We also suggest that this could favour the appearance of the spectral "f"-characterictics. While the derived β value does not change by adopting a lower wind terminal velocity, we show that a wrong V ∞ has a clear impact on the position of the star in the WLR diagram. The N and He abundances are very high, consistent with strong CNO mixing that could have been caused by the fast rotation, although we cannot discard a different origin with present data. Stellar evolutionary model predictions are consistent with the star being still a fast rotator. We find again the well-known mass-discrepancy for this star. Conclusions. We conclude that the star follows the WLR expected for its metallicity. The results are consistent with GHV-62024 being a fast rotator seen close to pole-on, strongly contaminated at the surface with CNO products and with a wind structure altered by the fast rotation but without modifying the global WLR. We suggest that this could be a general property of fast rotators.

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Section: The Wind Momentum Of Ghv-62024supporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

A peculiar Of star in the Local Group galaxy IC 1613

Herrero¹,

García²,

Puls³

et al. 2012

A&A

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“…While both Mokiem et al (2005Mokiem et al ( , 2006Mokiem et al ( , 2007a and Tramper et al (2011Tramper et al ( , 2014 used the V-band magnitude as a photometric anchor, we choose to use the K-band magnitude (M K ) to minimise the impact of uncertainties on the individual reddening of the objects in our sample. We determined M K using the VISTA observed K-band magnitude (Rubele et al 2012), adopting a distance modulus to the Tarantula nebula of 18.5 mag (see Paper I) and an average K-band extinction (A K ) of 0.21 mag (Maíz-Apellániz et al, in prep.).…”

Section: Atmosphere Fittingmentioning

confidence: 99%

The VLT-FLAMES Tarantula Survey

Grin

Ramírez-Agudelo

Koter

et al. 2017

A&A

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Context. The Tarantula region in the Large Magellanic Cloud contains the richest population of spatially resolved massive O-type stars known so far. This unmatched sample offers an opportunity to test models describing their main-sequence evolution and massloss properties. Aims. Using ground-based optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to determine stellar, photospheric and wind properties of 72 presumably single O-type giants, bright giants and supergiants and to confront them with predictions of stellar evolution and of line-driven mass-loss theories. Methods. We apply an automated method for quantitative spectroscopic analysis of O stars combining the non-LTE stellar atmosphere model fastwind with the genetic fitting algorithm pikaia to determine the following stellar properties: effective temperature, surface gravity, mass-loss rate, helium abundance, and projected rotational velocity. The latter has been constrained without taking into account the contribution from macro-turbulent motions to the line broadening.Results. We present empirical effective temperature versus spectral subtype calibrations at LMC-metallicity for giants and supergiants. The calibration for giants shows a +1kK offset compared to similar Galactic calibrations; a shift of the same magnitude has been reported for dwarfs. The supergiant calibrations, though only based on a handful of stars, do not seem to indicate such an offset. The presence of a strong upturn at spectral type O3 and earlier can also not be confirmed by our data. In the spectroscopic and classical Hertzsprung-Russell diagrams, our sample O stars are found to occupy the region predicted to be the core hydrogen-burning phase by Brott et al. (2011) andKöhler et al. (2015). For stars initially more massive than approximately 60 M ⊙ , the giant phase already appears relatively early on in the evolution; the supergiant phase develops later. Bright giants, however, are not systematically positioned between giants and supergiants at M init ∼ > 25 M ⊙ . At masses below 60 M ⊙ , the dwarf phase clearly precedes the giant and supergiant phases; however this behavior seems to break down at M init ∼ < 18 M ⊙ . Here, stars classified as late O III and II stars occupy the region where O9.5-9.7 V stars are expected, but where few such late O V stars are actually seen. Though we can not exclude that these stars represent a physically distinct group, this behaviour may reflect an intricacy in the luminosity classification at late O spectral subtype. Indeed, on the basis of a secondary classification criterion, the relative strength of Si iv to He i absorption lines, these stars would have been assigned a luminosity class IV or V. Except for five stars, the helium abundance of our sample stars is in agreement with the initial LMC composition. This outcome is independent of their projected spin rates. The aforementioned five stars present moderate projected rotational velocities (i.e., e sin i < 200 km s −1 ) and hence do no...

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“…Solving the radiative transfer across the atmosphere of massive stars is a complex and demanding task, and adequate atmospheric codes became available only in the past decade. Complex radiative transfer models such as CMFGEN (Hillier & Miller 1998), PoWR (Hamann et al 2006), and FASTWIND (Puls et al 2006), that take into account the necessary physics to study the radiation transport across the atmosphere and wind, have been separately employed to analyze observations of O stars (e.g., Hillier et al 2003;Martins et al 2005;Bouret et al 2003Bouret et al , 2005Puls et al 2006;Marcolino et al 2009;Najarro et al 2011;Repolust et al 2004;Mokiem et al 2005Mokiem et al , 2007Tramper et al 2011), LBVs (e.g., Hillier et al 2001;Groh et al 2006Groh et al , 2009Groh et al , 2011Groh et al , 2012Najarro et al 2009), and WRs (e.g., Hillier & Miller 1999;Dessart et al 2000;Gräfener & Hamann 2005;Sander et al 2012). From the stellar evolution perspective, the main advances have been to include the effects of rotation and magnetic fields, and improve opacities and mass-loss recipes.…”

Section: Introductionmentioning

confidence: 99%

The evolution of massive stars and their spectra

Groh

Meynet

Ekström

et al. 2014

A&A

158

189

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For the first time, the interior and spectroscopic evolution of a massive star is analyzed from the zero-age main sequence (ZAMS) to the pre-supernova (SN) stage. For this purpose, we combined stellar evolution models using the Geneva code and stellar atmospheric/wind models using CMFGEN. With our approach, we were able to produce observables, such as a synthetic high-resolution spectrum and photometry, thereby aiding the comparison between evolution models and observed data. Here we analyze the evolution of a nonrotating 60 M star and its spectrum throughout its lifetime. Interestingly, the star has a supergiant appearance (luminosity class I) even at the ZAMS. We find the following evolutionary sequence of spectral types: O3 I (at the ZAMS), O4 I (middle of the H-core burning phase), B supergiant (BSG), B hypergiant (BHG), hot luminous blue variable (LBV; end of H-core burning), cool LBV (H-shell burning through the beginning of the He-core burning phase), rapid evolution through late WN and early WN, early WC (middle of He-core burning), and WO (end of He-core burning until core collapse). We find the following spectroscopic phase lifetimes: 3.22 × 10 6 yr for the O-type, 0.34 × 10 5 yr (BSG), 0.79 × 10 5 yr (BHG), 2.35 × 10 5 yr (LBV), 1.05 × 10 5 yr (WN), 2.57 × 10 5 yr (WC), and 3.80 × 10 4 yr (WO). Compared to previous studies, we find a much longer (shorter) duration for the early WN (late WN) phase, as well as a long-lived LBV phase. We show that LBVs arise naturally in single-star evolution models at the end of the MS when the mass-loss rate increases as a consequence of crossing the bistability limit. We discuss the evolution of the spectra, magnitudes, colors, and ionizing flux across the star's lifetime, and the way they are related to the evolution of the interior. We find that the absolute magnitude of the star typically changes by ∼6 mag in optical filters across the evolution, with the star becoming significantly fainter in optical filters at the end of the evolution, when it becomes a WO just a few 10 4 years before the SN explosion. We also discuss the origin of the different spectroscopic phases (i.e., O-type, LBV, WR) and how they are related to evolutionary phases (H-core burning, H-shell burning, He-core burning).

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On the Mass-Loss Rate of Massive Stars in the Low-Metallicity Galaxies Ic 1613, Wlm, and NGC 3109

Cited by 53 publications

References 45 publications

A peculiar Of star in the Local Group galaxy IC 1613

A peculiar Of star in the Local Group galaxy IC 1613

The VLT-FLAMES Tarantula Survey

The evolution of massive stars and their spectra

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