An obstacle to the late evolution of massive stars

Jager, C. de; Nieuwenhuijzen, H.

doi:10.1093/mnras/290.3.l50

Cited by 48 publications

(48 citation statements)

References 1 publication

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“…Oudmaijer et al (1996) found that IRC +10 420 increased in temperature by >1000 K over the past twenty years, with similar behaviour inferred for HD 179821 (Patel et al 2008). In contrast HR 8752 has undergone two red loops in the HR diagram over the past thirty years, each of approximately 10 years duration (de Jager & Nieuwenhuijzen 1997). Similar excursions to cool temperatures have been observed for ρ Cas (Lobel et al 2003) although the duration of these events is significantly shorter (≤2 yrs).…”

Section: The Yellow Hypergiantssupporting

confidence: 70%

A serendipitous survey for variability amongst the massive stellar population of Westerlund 1

Clark¹,

Ritchie

Negueruela

2010

A&A

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Aims. Massive stars are known to demonstrate significant spectroscopic and photometric variability over a wide range of timescales. However the physical mechanisms driving this behaviour remain poorly understood. Westerlund 1 presents an ideal laboratory for studying these processes in a rich, coeval population of post-main sequence stars and we present a pathfinding study aimed at characterising their variability. Methods. To do this we utilised the large body of spectroscopic and photometric data that has accumulated for Wd1 during the past decade of intensive studies, supplemented with the sparser historical observations extending back to the early 1960s. Results. Despite the heterogeneous nature of this dataset, we were able to identify both spectroscopic and photometric variability amongst every class of evolved massive star present within Wd 1. Spectroscopic variability attributable to both wind asphericity and photospheric pulsations was present amongst both the hot and cool hypergiants and the former, also with the Wolf Rayets. Given the limitations imposed by the data, we were unable to determine the physical origin of the wind structure inferred for the OB supergiants, noting that it was present in both single pulsating and binary stars. In contrast we suspect that the inhomogineities in the winds of the Wolf Rayets are driven by binary interactions and, conversely, by pulsations in at least one of the cool hypergiants. Photospheric pulsations were found for stars ranging from spectral types as early as O9 I through to the mid F Ia + yellow hypergiants -with a possible dependence on the luminosity class amongst the hot supergiants. The spectroscopically variable red supergiants (M2-5 Ia) are also potential pulsators but require further observations to confirm this hypothesis. Given these findings it was therefore rather surprising that, with the exception of W243, no evidence of the characteristic excursions of both luminous blue variables and yellow hypergiants was found. Nevertheless, future determination of the amplitude and periodicity of these pulsations as a function of temperature, luminosity and evolutionary state holds out the tantalising possibility of constraining the nature of the physical mechanisms driving the instabilities that constrain and define stellar evolution in the upper reaches of the HR diagram. Relating to this, the lack of secular evolution amongst the cool hypergiants and the presence of both high-luminosity yellow hypergiants and red supergiants within Wd1 potentially place strong constraints on post-main sequence evolutionary pathways, with the latter result apparently contradicting current theoretical predictions for >25 M stars at solar metallicites.

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Section: The Yellow Hypergiantssupporting

confidence: 70%

A serendipitous survey for variability amongst the massive stellar population of Westerlund 1

Clark¹,

Ritchie

Negueruela

2010

A&A

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“…Once the luminosity was fixed , we explored a broad range in temperatures, which roughly corresponds to the domain of LBVs and Yellow Supergiants in the H-R diagram: 31 000 K-8000 K. This range is based on the works of Gummersbach et al (1995), Szeifert et al (1996) and de Jager & Nieuwenhuijzen (1997).…”

Section: Methodsmentioning

confidence: 99%

HR Carinae: New spectroscopic data and physical parameters

Machado

Araújo

Pereira

et al. 2002

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“…yellow hypergiants are hypothesised to evolve from the red to the blue, crossing the so-called Yellow Void, a hitherto fairly empty region in the HR diagram (de Jager & Nieuwenhuijzen 1997). Some of them have been observed to undergo strong mass-loss events, creating a pseudo-photosphere making them appear to cross this Yellow Void again, but now back to the red (e.g.…”

Section: The Origin Of the Na I Emissionmentioning

confidence: 99%

Neutral and ionised gas around the post-red supergiant IRC +10 420 at AU size scales

Oudmaijer

Wit

2013

A&A

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Context. IRC +10 420 is one of the few known massive stars in rapid transition from the red supergiant phase to the Wolf-Rayet or luminous blue variable phase. Aims. The star has an ionised wind and using the Brγ line we assess the mass-loss on spatial scales of ∼1 AU. Methods. We present new VLT Interferometer AMBER data which are combined with all other AMBER data present in the literature. The final dataset covers a position angle range of ∼180 • and baselines up to 110 m. The spectrally dispersed visibilities, differential phases and line flux are conjointly analysed and modelled. We also present the first AMBER/FINITO observations which cover a larger wavelength range and allow us to observe the Na i doublet at 2.2 μm. The data are complemented by X-Shooter data, which provide a higher spectral resolution view.Results. The Brγ emission line and the Na i doublet are both spatially resolved. After correcting the AMBER data for the fact that the lines are not spectrally resolved, we find that Brγ traces a ring with a diameter of 4.18 mas, in agreement with higher spectral resolution data. We consider a geometric model in which the Brγ emission emerges from the top and bottom rings of an hour-glass shaped structure, viewed almost pole-on. It provides satisfactory fits to most visibilities and differential phases. The fact that we detect line emission from a neutral metal like Na i within the ionised region, a very unusual occurrence, suggests the presence of a dense pseudo-photosphere. Conclusions. The ionised wind can be reproduced with a polar wind, which could well have the shape of an hour-glass. Closer in, the resolved Na i emission is found to occur on scales barely larger than the continuum. This fact and that many yellow hypergiants exhibit this comparatively rare emission hints at the presence of a "Yellow" or even "White Wall" in the Hertzsprung-Russell diagram, preventing them from visibly evolving to the blue.

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An obstacle to the late evolution of massive stars

Cited by 48 publications

References 1 publication

A serendipitous survey for variability amongst the massive stellar population of Westerlund 1

A serendipitous survey for variability amongst the massive stellar population of Westerlund 1

HR Carinae: New spectroscopic data and physical parameters

Neutral and ionised gas around the post-red supergiant IRC +10 420 at AU size scales

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