The Discovery of a Rare Wo-Type Wolf–rayet Star in the Large Magellanic Cloud

Neugent, Kathryn F.; Massey, Philip; Morrell, N.

doi:10.1088/0004-6256/144/6/162

Cited by 24 publications

(43 citation statements)

References 19 publications

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“…In addition to the 108 WN stars, only 24 WC stars plus two WR stars with prominent oxygen lines (WO stars) were discovered (Barlow & Hummer 1982;Neugent et al 2012). The composition of the WR population is thus very different from our Galaxy, where the ratio of WN to WC stars is close to unity.…”

Section: Sample Selectionmentioning

confidence: 68%

“…A list of the seven newly discovered WR stars, six of them WN-type stars, can be found in Table 3 of Neugent et al (2012). Thus, the number of known WN stars in the LMC amounts to 108, although two of these new detections are precarious.…”

Section: Sample Selectionmentioning

confidence: 99%

“…However, Foellmi et al (2003b) could not confirm this detection. Neugent et al (2012) also list LH 90β-6 as a new WN star. However, according to Massey et al (2000), this is an alias of TSWR 1, which was resolved into multiple components by Walborn et al (1999) and incorporated in the BAT99 catalog with the number BAT99 78.…”

Section: Sample Selectionmentioning

confidence: 99%

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The Wolf-Rayet stars in the Large Magellanic Cloud

Hainich

Rühling

Todt

et al. 2014

A&A

201

310

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Context. Massive stars, although being important building blocks of galaxies, are still not fully understood. This especially holds true for Wolf-Rayet (WR) stars with their strong mass loss, whose spectral analysis requires adequate model atmospheres. Aims. Following our comprehensive studies of the WR stars in the Milky Way, we now present spectroscopic analyses of almost all known WN stars in the LMC. Methods. For the quantitative analysis of the wind-dominated emission-line spectra, we employ the Potsdam Wolf-Rayet (PoWR) model atmosphere code. By fitting synthetic spectra to the observed spectral energy distribution and the available spectra (ultraviolet and optical), we obtain the physical properties of 107 stars. Results. We present the fundamental stellar and wind parameters for an almost complete sample of WN stars in the LMC. Among those stars that are putatively single, two different groups can be clearly distinguished. While 12% of our sample are more luminous than 10 6 L and contain a significant amount of hydrogen, 88% of the WN stars, with little or no hydrogen, populate the luminosity range between log (L/L ) = 5.3 ... 5.8. Conclusions. While the few extremely luminous stars (log (L/L ) > 6), if indeed single stars, descended directly from the main sequence at very high initial masses, the bulk of WN stars have gone through the red-supergiant phase. According to their luminosities in the range of log (L/L ) = 5.3 ... 5.8, these stars originate from initial masses between 20 and 40 M . This mass range is similar to the one found in the Galaxy, i.e. the expected metallicity dependence of the evolution is not seen. Current stellar evolution tracks, even when accounting for rotationally induced mixing, still partly fail to reproduce the observed ranges of luminosities and initial masses. Moreover, stellar radii are generally larger and effective temperatures correspondingly lower than predicted from stellar evolution models, probably due to subphotospheric inflation.

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Section: Sample Selectionmentioning

confidence: 68%

Section: Sample Selectionmentioning

confidence: 99%

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The Wolf-Rayet stars in the Large Magellanic Cloud

Hainich

Rühling

Todt

et al. 2014

A&A

201

310

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“…Spurred on by the discovery of a previously unknown WO-type Wolf-Rayet (WR) star in the Large Magellanic Cloud (LMC) by Neugent et al (2012a), we undertook a multi-year search for WRs in the Magellanic Clouds. So far we have imaged the entire optical disks of the Magellanic Clouds and discovered 16 new WRs (Massey et al 2014(Massey et al , 2017.…”

Section: Discoverymentioning

confidence: 99%

The Evolution and Physical Parameters of WN3/O3s: A New Type of Wolf–Rayet Star^*

Neugent

Massey

Hillier

et al. 2017

ApJ

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As part of a search for Wolf-Rayet (WR) stars in the Magellanic Clouds, we have discovered a new type of WR star in the Large Magellanic Cloud (LMC). These stars have both strong emission lines, as well as He ii and Balmer absorption lines and spectroscopically resemble a WN3 and O3V binary pair. However, they are visually too faint to be WN3+O3V binary systems. We have found nine of these WN3/O3s, making up ∼ 6% of the population of LMC WRs. Using cmfgen, we have successfully modeled their spectra as single stars and have compared the physical parameters with those of more typical LMC WNs. Their temperatures are around 100,000 K, a bit hotter than the majority of WN stars (by around 10,000 K) although a few hotter WNs are known. The abundances are what you would expect for CNO equilibrium. However, most anomalous are their mass-loss rates which are more like that of an O-type star than a WN star. While their evolutionary status is uncertain, their low mass-loss rates and wind velocities suggest that they are not products of homogeneous evolution. It is possible instead that these stars represent an intermediate stage between O stars and WNs. Since WN3/O3 stars are unknown in the Milky Way, we suspect that their formation depends upon metallicity, and we are investigating this further by a deep survey in M33, which posses a metallicity gradient.

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“…A large fraction of massive stars might also undergo interactions in close binaries (Sana et al, 2012), and thus follow a quite different evolutionary path. RSGs are easily seen in external galaxies (Lançon et al, 2009;Drout et al, 2012;Neugent et al, 2012) which makes them also interesting objects because they can be used as metallicity or distance indicators. Davies et al (2010) and Bergemann et al (2012) proposed the RSGs as metallicity indicators, showing that the determination of Z is robust even when only modest resolution (R = 1 − 3000) is available.…”

Section: Why Red Supergiants Are Interesting Objectsmentioning

confidence: 99%

Red supergiants and stellar evolution

Ekström

Georgy

Meynet

et al. 2013

EAS Publications Series

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Abstract. We review the significant role played by red supergiants (RSGs) in stellar populations, and some challenges and questions they raise for theoretical stellar evolution. We present how metallicity and rotation modify the way stars go to the red part of the HertzsprungRussell diagram or come back from it, and how RSGs might keep a trace of their main-sequence evolution. We compare theoretical population ratios with observed ones.

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The Discovery of a Rare Wo-Type Wolf–rayet Star in the Large Magellanic Cloud

Cited by 24 publications

References 19 publications

The Wolf-Rayet stars in the Large Magellanic Cloud

The Wolf-Rayet stars in the Large Magellanic Cloud

The Evolution and Physical Parameters of WN3/O3s: A New Type of Wolf–Rayet Star^*

Red supergiants and stellar evolution

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The Discovery of a Rare Wo-Type Wolf–rayet Star in the Large Magellanic Cloud

Cited by 24 publications

References 19 publications

The Wolf-Rayet stars in the Large Magellanic Cloud

The Wolf-Rayet stars in the Large Magellanic Cloud

The Evolution and Physical Parameters of WN3/O3s: A New Type of Wolf–Rayet Star*

Red supergiants and stellar evolution

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Product

Resources

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The Evolution and Physical Parameters of WN3/O3s: A New Type of Wolf–Rayet Star^*