The Asymmetric Nebula Surrounding the Extreme Red Supergiant Vy Canis Majoris

Smith, Nathan; Humphreys, R. M.; Davidson, Kris; Gehrz, R. D.; Schuster, Michael J.; Krautter, J.

doi:10.1086/318748

Cited by 144 publications

(265 citation statements)

References 57 publications

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“…This is consistent with its position further from the cluster centre than either W20 or W26. The derived massloss rate is comparable to the mass-loss rates found for field RSGs, which range from 10 −6 -10 −4 M yr −1 (Jura & Kleinmann 1990;Sylvester et al 1998), although transient rates as high as ∼10 −3 M yr −1 are seen in NML Cyg and VY Cma (Blöcker et al 2001;Smith et al 2001) and as low as a ∼few 10 −7 M in μ Cep (de Wit et al 2008) have been observed.…”

Section: The Red Supergiantssupporting

confidence: 76%

“…Of the Galactic examples, Schuster et al (2006) used the HST/WFPC2 to identify compact (r ≤ 0.003 pc) nebulae associated with NML Cyg, VX Sgr and S Per, with Morris & Jura (1983) also associating a much larger (>1 pc) H ii region with NML Cyg. de Wit et al (2008) report the presence a nebula around μ Cep at 25 microns (r ∼ 0.03 pc); a comparably sized nebulae surrounds VY CMa (r ∼ 0.04 pc in HST/WFPC2 images; Smith et al 2001). Finally Serabyn et al (1991) and Yusef-Zadeh & Morris (1991) report the presence of an asymmetric nebula (∼1pc in length) around the Galactic Centre RSG IRS7 at both near-IR and radio wavelengths.…”

Section: The Red Supergiantsmentioning

confidence: 99%

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Radio emission from the massive stars in the galactic super star cluster Westerlund 1

Dougherty

Clark

Negueruela

et al. 2010

A&A

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Aims. Current mass-loss rate estimates imply that main sequence line-driven winds are not sufficient to strip away the H-rich envelope to yield Wolf-Rayet (WR) stars. The rich transitional population of the young massive cluster Westerlund 1 (Wd 1) provides an ideal laboratory to observe and constrain mass-loss processes throughout the transitional phase of stellar evolution. Methods. We present an analysis of deep radio continuum observations of Wd 1 obtained with the Australia Telescope Compact Array at four frequency bands that permit investigation of the intrinsic characteristics of the radio emission. Results. We detect 18 cluster members, a sample dominated by the cool hypergiants, with additional detections amongst the hotter OB supergiants and WR stars. The radio properties of the sample are diverse, with thermal, non-thermal and composite thermal/nonthermal sources present. Mass-loss rates determined for stars with partially optically thick stellar winds are ∼10 −5 M yr −1 across all spectral types, insufficient to enable the formation of WRs during a massive star lifetime, and the stars must undergo a period of greatly enhanced mass loss. The sgB[e] star W9, the brightest radio source in Wd 1, may provide an example, with a current mass-loss rate an order of magnitude higher than the other cluster members, and an extended nebula interpreted as a wind from an earlier epoch with a density ∼3× the current wind. Such an envelope structure in W9 is reminiscent of luminous blue variables, and one that shows evidence of two eras of high, possibly eruptive mass loss. Surprisingly, three of the OB supergiants are detected, implying unusually dense winds, though they are embedded in more extended emission regions that may influence the derived parameters. They also may have composite spectra, suggesting binarity, which can lead to a higher flux than expected from a stellar wind. Spatially resolved nebulae are associated with three of the four RSGs and three of the six YHGs in the cluster, which are due to quiescent mass loss rather than outbursts. The extended nebulae of W20 and W26 have a cometary morphology, implying significant interaction with either the intracluster medium or cluster wind. For some of the cool star winds, the ionizing source may be a companion star though the cluster radiation density is sufficiently high to provide the necessary ionizing radiation. Five WR stars are detected with composite spectra, interpreted as arising in colliding-wind binaries.

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Section: The Red Supergiantssupporting

confidence: 76%

Section: The Red Supergiantsmentioning

confidence: 99%

Radio emission from the massive stars in the galactic super star cluster Westerlund 1

Dougherty

Clark

Negueruela

et al. 2010

A&A

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“…Additionally, these central to integrated flux ratios, as well as dedicated measurements in the spectra, reveal that the line to continuum ratios are constant to within 5% over the whole field of view, at all PACS wavelengths, the only exception being the [Cii] line at 157.74 μm, which has a stronger integrated flux due Smith et al (2001).…”

Section: Observational Resultsmentioning

confidence: 66%

PACS and SPIRE spectroscopy of the red supergiant VY CMa

Royer¹,

Decin

Wesson

et al. 2010

A&A

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With a luminosity >10 5 L and a mass-loss rate of ∼2 × 10 −4 M yr −1 , the red supergiant VY CMa truly is a spectacular object. Because of its extreme evolutionary state, it could explode as supernova any time. Studying its circumstellar material, into which the supernova blast will run, provides interesting constraints on supernova explosions and on the rich chemistry taking place in such complex circumstellar envelopes. We have obtained spectroscopy of VY CMa over the full wavelength range offered by the PACS and SPIRE instruments of Herschel, i.e. 55-672 micron. The observations show the spectral fingerprints of more than 900 spectral lines, of which more than half belong to water. In total, we have identified 13 different molecules and some of their isotopologues. A first analysis shows that water is abundantly present, with an ortho-to-para ratio as low as ∼1.3:1, and that chemical non-equilibrium processes determine the abundance fractions in the inner envelope.

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“…Very recently, precise parallax measurements by Choi et al (2008) and Zhang et al (2012) significantly improved the distance estimate to about 1.2 kpc, which together with recent accurate broad-band photometry by Smith et al (2001) points to a luminosity of about 3 × 10 5 L . VY CMa is embedded in a large optical nebula (Herbig 1972) and is also an extended object in the infrared (McCarthy & Low 1975).…”

Section: Introductionmentioning

confidence: 91%

Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry

Wittkowski¹,

Hauschildt

Arroyo-Torres

et al. 2012

A&A

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Aims. We investigate the atmospheric structure and fundamental properties of the red supergiant VY CMa. Methods. We obtained near-infrared spectro-interferometric observations of VY CMa with spectral resolutions of 35 and 1500 using the AMBER instrument at the VLTI. Results. The visibility data indicate the presence of molecular layers of water vapor and CO in the extended atmosphere with an asymmetric morphology. The uniform disk diameter in the water band around 2.0 μm is increased by ∼20% compared to the nearcontinuum bandpass at 2.20-2.25 μm, and in the CO band at 2.3-2.5 μm it is increased by up to ∼50%. The closure phases indicate relatively small deviations from point symmetry close to the photospheric layer, and stronger deviations in the extended H 2 O and CO layers. Making use of the high spatial and spectral resolution, a near-continuum bandpass can be isolated from contamination by molecular and dusty layers, and the Rosseland-mean photospheric angular diameter is estimated to 11.3 ± 0.3 mas based on a PHOENIX atmosphere model. Together with recent high-precision estimates of the distance and spectro-photometry, this estimate corresponds to a radius of 1420 ± 120 R and an effective temperature of 3490 ± 90 K. Conclusions. VY CMa exhibits asymmetric, possibly clumpy, atmospheric layers of H 2 O and CO, which are not co-spatial, within a larger elongated dusty envelope. Our revised fundamental parameters put VY CMa close to the Hayashi limit of recent evolutionary tracks of initial mass 25 M with rotation or 32 M without rotation, shortly before evolving blueward in the HR-diagram.

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The Asymmetric Nebula Surrounding the Extreme Red Supergiant Vy Canis Majoris

Cited by 144 publications

References 57 publications

Radio emission from the massive stars in the galactic super star cluster Westerlund 1

Radio emission from the massive stars in the galactic super star cluster Westerlund 1

PACS and SPIRE spectroscopy of the red supergiant VY CMa

Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry

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