Asymmetrical nebula of the M33 variable GR290 (WR/LBV)

Maryeva, O. V.; Koenigsberger, Gloria; Карпов, С.; Lozinskaya, T. A.; Egorov, Oleg V.; Rossi, C.; Calabresi, M.; Viotti, R.

doi:10.1051/0004-6361/201936840

Cited by 6 publications

(9 citation statements)

References 30 publications

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“…The emission from its first-overtone bands arises in the K-band around 2.3 µm and has been detected in about 50% of the B[e]SGs [19]. Besides the main isotope 12 CO, emission from 13 CO is seen in considerable amounts [20,21], confirming that the matter from which the disks have formed contains processed material that must have been released from the stellar surface [22].…”

Section: B[e] Supergiantsmentioning

confidence: 98%

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Dense Molecular Environments of B[e] Supergiants and Yellow Hypergiants

et al. 2023

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Massive stars expel large amounts of mass during their late evolutionary phases. We aim to unveil the physical conditions within the warm molecular environments of B[e] supergiants (B[e]SGs) and yellow hypergiants (YHGs), which are known to be embedded in circumstellar shells and disks. We present K-band spectra of two B[e]SGs from the Large Magellanic Cloud and four Galactic YHGs. The CO band emission detected from the B[e]SGs LHA 120-S 12 and LHA 120-S 134 suggests that these stars are surrounded by stable rotating molecular rings. The spectra of the YHGs display a rather diverse appearance. The objects 6 Cas and V509 Cas lack any molecular features. The star [FMR2006] 15 displays blue-shifted CO bands in emission, which might be explained by a possible close to pole-on oriented bipolar outflow. In contrast, HD 179821 shows blue-shifted CO bands in absorption. While the star itself is too hot to form molecules in its outer atmosphere, we propose that it might have experienced a recent outburst. We speculate that we currently can only see the approaching part of the expelled matter because the star itself might still block the receding parts of a (possibly) expanding gas shell.

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Section: B[e] Supergiantsmentioning

confidence: 98%

“…This implies that the ring of CO gas around LHA 120-S 12 is stable on longer timescales. 13 CO values for LHA 120-S 12 and LHA 120-S 134 have been derived by [20,21], respectively. Our Phoenix spectra do not reach the wavelength region of the 13 CO bands.…”

Section: Modeling Of the Co Band And Pfund Line Emissionmentioning

confidence: 99%

Dense Molecular Environments of B[e] Supergiants and Yellow Hypergiants

et al. 2023

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“…Our allegation that the driving stellar object of NGC 6888 is not, despite the findings of Stock & Barlow (2014); Rubio et al (2020), a single star, is supported by the detection of periodical modulation in line emission from the Wolf-Rayet star WR 134, interpretable as an inhomogeneous outflow (Morel et al 1998) or as a trace of a so far undetected close companion (Meyer et al 2018). The close companions to evolved massive stars Koenigsberger & Schmutz (2020) and the circumstellar nebulae of extragalactic Wolf-Rayet stars such as GR290 in the Galaxy M33 (Maryeva et al 2018(Maryeva et al , 2020) also support our arguments. All this motivates further investigations of that problem.…”

Section: What Makes Ngc 6888 Asymmetric ?mentioning

confidence: 99%

On the bipolarity of Wolf-Rayet nebulae

Meyer

2021

Preprint

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Wolf-Rayet stars are amongst the rarest but also most intriguing massive stars. Their extreme stellar winds induce famous multi-wavelength circumstellar gas nebulae of various morphologies, spanning from circles and rings to bipolar shapes. This study is devoted to the investigation of the formation of young, asymmetric Wolf-Rayet gas nebulae and we present a 2.5dimensional magneto-hydrodynamical toy model for the simulation of Wolf-Rayet gas nebulae generated by wind-wind interaction. Our method accounts for stellar wind asymmetries, rotation, magnetisation, evolution and mixing of materials. It is found that the morphology of the Wolf-Rayet nebulae of blue supergiant ancestors is tightly related to the wind geometry and to the stellar phase transition time interval, generating either a broadened peanut-like or a collimated jet-like gas nebula. Radiative transfer calculations of our Wolf-Rayet nebulae for dust infrared emission at 24 µm show that the projected diffuse emission can appear as oblate, bipolar, ellipsoidal or ring structures. Important projection effects are at work in shaping observed Wolf-Rayet nebulae. This might call a revision of the various classifications of Wolf-Rayet shells, which are mostly based on their observed shape. Particularly, our models question the possibility of producing pre-Wolf-Rayet wind asymmetries, responsible for bipolar nebulae like NGC 6888, within the single red supergiant evolution channel scenario. We propose that bipolar Wolf-Rayet nebulae can only be formed within the red supergiant scenario by multiple/merged massive stellar systems, or by single high-mass stars undergoing additional, e.g. blue supergiant, evolutionary stages prior to the Wolf-Rayet phase.

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“…From our study, we expect that variability and phenomenology similar to that of classical S Dor LBVs could be present in other regions of the HR diagram. HD5980A (Koenigsberger et al 2010), MCA-1B (Smith et al 2020), and GR290 (Polcaro et al 2011;Clark et al 2012;Maryeva et al 2020) are possible representative examples of transitions involving the sonic points in the temperature range of the iron opacity bump, as indicated by the model atmospheres by Georgiev et al (2011). Their variations appear to share a quiescent phase at surface temperature ≈30 kK with the classical S Dor variables, but experience blueward rather than redward excursions as they potentially cross the iron-instead of the helium-minimum mass-loss rate (see Grassitelli et al 2018, who first introduced the iron-minimum mass-loss rate).…”

Section: Appendix C: Opacity Tablesmentioning

confidence: 99%

Wind-envelope interaction as the origin of the slow cyclic brightness variations of luminous blue variables

Grassitelli

Langer

Mackey

et al. 2021

A&A

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Luminous blue variables (LBVs) are hot, very luminous massive stars displaying large quasi-periodic variations in brightness, radius, and photospheric temperature on timescales of years to decades. The physical origin of this variability, called S Doradus cycle after its prototype, has remained elusive. We study the feedback of stellar wind mass-loss on the envelope structure in stars near the Eddington limit. We calculated a time-dependent hydrodynamic stellar evolution, applying a stellar wind mass-loss prescription with a temperature dependence inspired by the predicted systematic increase in mass-loss rates below 25 kK. We find that when the wind mass-loss rate crosses a well-defined threshold, a discontinuous change in the wind base conditions leads to a restructuring of the stellar envelope. The induced drastic radius and temperature changes, which occur on the thermal timescale of the inflated envelope, in turn impose mass-loss variations that reverse the initial changes, leading to a cycle that lacks a stationary equilibrium configuration. Our proof-of-concept model broadly reproduces the typical observational phenomenology of the S Doradus variability. We identify three key physical ingredients that are required to trigger the instability: inflated envelopes in close proximity to the Eddington limit, a temperature range where decreasing opacities do not lead to an accelerating outflow, and a mass-loss rate that increases with decreasing temperature, crossing a critical threshold value within this temperature range. Our scenario and model provide testable predictions, and open the door for a consistent theoretical treatment of the LBV phase in stellar evolution, with consequences for their further evolution as single stars or in binary systems.

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Asymmetrical nebula of the M33 variable GR290 (WR/LBV)

Cited by 6 publications

References 30 publications

Dense Molecular Environments of B[e] Supergiants and Yellow Hypergiants

Dense Molecular Environments of B[e] Supergiants and Yellow Hypergiants

On the bipolarity of Wolf-Rayet nebulae

Wind-envelope interaction as the origin of the slow cyclic brightness variations of luminous blue variables

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