RED SUPERGIANTS AS POTENTIAL TYPE IIn SUPERNOVA PROGENITORS: SPATIALLY RESOLVED 4.6 μm CO EMISSION AROUND VY CMa AND BETELGEUSE

Smith, Nathan; Hinkle, Kenneth H.; Ryde, Nils

doi:10.1088/0004-6256/137/3/3558

Cited by 181 publications

(187 citation statements)

References 126 publications

(175 reference statements)

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“…For instance, van Loon et al (2005) obtained that dust-enshrouded RSGs present mass-loss rates that are a factor of 3-50 times higher than the rate of de Jager et al (1988). Humphreys et al (1997Humphreys et al ( , 2005 and Smith et al (2009) also indicated that the RSG star VY CMa went through important episodic mass ejections 500-1000 years ago. Moriya et al (2011) reached similar conclusions, studying the luminosity curve of SNe with RSG progenitors.…”

Section: Discussion Of Various Possible Origins For the Low-luminositmentioning

confidence: 99%

Grids of stellar models with rotation

Georgy

Ekström

Meynet

et al. 2012

A&A

305

364

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Context. In recent years, many very interesting observations have appeared concerning the positions of Wolf-Rayet (WR) stars in the Hertzsprung-Russell diagram (HRD), the number ratios of WR stars, the nature of Type Ibc supernova (SN) progenitors, long and soft gamma ray bursts (LGRB), and the frequency of these various types of explosive events. These observations represent key constraints on massive star evolution. Aims. We study, in the framework of the single-star evolutionary scenario, how rotation modifies the evolution of a given initial mass star towards the WR phase and how it impacts the rates of Type Ibc SNe. We also discuss the initial conditions required to obtain collapsars and LGRB. Methods. We used a recent grid of stellar models computed with and without rotation to make predictions concerning the WR populations and the frequency of different types of core-collapse SNe. Current rotating models were checked to provide good fits to the following features: solar luminosity and radius at the solar age, main-sequence width, red-giant and red-supergiant (RSG) positions in the HRD, surface abundances, and rotational velocities. Results. Rotating stellar models predict that about half of the observed WR stars and at least half of the Type Ibc SNe may be produced through the single-star evolution channel. Rotation increases the duration of the WNL and WNC phases, while reducing those of the WNE and WC phases, as was already shown in previous works. Rotation increases the frequency of Type Ic SNe. The upper mass limit for Type II-P SNe is ∼19.0 M for the non rotating models and ∼16.8 M for the rotating ones. Both values agree with observations. Moreover, present rotating models provide a very good fit to the progenitor of SN 2008ax. We discuss future directions of research for further improving the agreement between the models and the observations. We conclude that the mass-loss rates in the WNL and RSG phases are probably underestimated at present. We show that up to an initial mass of 40 M , a surface magnetic field inferior to about 200 G may be sufficient to produce some braking. Much lower values are needed at the red supergiant stage. We suggest that the presence/absence of any magnetic braking effect may play a key role in questions regarding rotation rates of young pulsars and the evolution leading to LGRBs.

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Section: Discussion Of Various Possible Origins For the Low-luminositmentioning

confidence: 99%

Grids of stellar models with rotation

Georgy

Ekström

Meynet

et al. 2012

A&A

305

364

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“…3) shows a very extended (≈5 in diameter) asymmetric dusty envelope, with extensions in the southwestern, northwestern and northeastern directions, similar to the positions of the three plumes we observed with NACO. Smith et al (2009) recently found a mildly clumpy, spherical shell around Betelgeuse in CO emission, from spatially resolved spectroscopy at λ ≈ 4.6 μm. Some interesting structures were detected ≈1 west of the star, but their identification to a mass loss event or envelope asymmetry is unclear.…”

Section: Previous High Angular Resolution Observationsmentioning

confidence: 98%

The close circumstellar environment of Betelgeuse

Kervella¹,

Verhoelst

Ridgway

et al. 2009

A&A

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Context. Betelgeuse is one the largest stars in the sky in terms of angular diameter. Structures on the stellar photosphere have been detected in the visible and near-infrared as well as a compact molecular environment called the MOLsphere. Mid-infrared observations have revealed the nature of some of the molecules in the MOLsphere, some being the precursor of dust. Aims. Betelgeuse is an excellent candidate to understand the process of mass loss in red supergiants. Using diffraction-limited adaptive optics (AO) in the near-infrared, we probe the photosphere and close environment of Betelgeuse to study the wavelength dependence of its extension, and to search for asymmetries. Methods. We obtained AO images with the VLT/NACO instrument, taking advantage of the "cube" mode of the CONICA camera to record separately a large number of short-exposure frames. This allowed us to adopt a "lucky imaging" approach for the data reduction, and obtain diffraction-limited images over the spectral range 1.04−2.17 μm in 10 narrow-band filters. Results. In all filters, the photosphere of Betelgeuse appears partly resolved. We identify an asymmetric envelope around the star, with in particular a relatively bright "plume" extending in the southwestern quadrant up to a radius of approximately six times the photosphere. The CN molecule provides an excellent match to the 1.09 μm bandhead in absorption in front of the stellar photosphere, but the emission spectrum of the plume is more difficult to interpret. Conclusions. Our AO images show that the envelope surrounding Betelgeuse has a complex and irregular structure. We propose that the southwestern plume is linked either to the presence of a convective hot spot on the photosphere, or to the rotation of the star.

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“…Although the extended envelope of Betelgeuse is thought to be inhomogeneous and asymmetric close to the star, on much larger scales, and more importantly on the scales that we are interested in, the outflow is largely spherically symmetric (Smith et al 2009). Furthermore, as discussed in Harper (2010), the massloss mechanism for M supergiant winds is not well understood.…”

Section: The Stellar Windmentioning

confidence: 98%

3D simulations of Betelgeuse’s bow shock

Mohamed

Mackey²,

Langer³

2012

A&A

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Betelgeuse, the bright, cool red supergiant in Orion, is moving supersonically relative to the local interstellar medium. The star emits a powerful stellar wind that collides with this medium, forming a cometary structure, a bow shock, pointing in the direction of motion. We present the first 3D hydrodynamic simulations of the formation and evolution of Betelgeuse's bow shock. The models include realistic low-temperature cooling and cover a range of plausible interstellar medium densities of 0.3-1.9 cm −3 and stellar velocities of 28-73 km s −1 . We show that the flow dynamics and morphology of the bow shock differ substantially because of the growth of Rayleigh-Taylor or Kelvin-Helmholtz instabilities. The former dominate the models with slow stellar velocities resulting in a clumpy bow shock substructure, whereas the latter produce a smoother, more layered substructure in the fast models. If the mass in the bow shock shell is low, as seems to be implied by the AKARI luminosities (∼3 × 10 −3 M ), then Betelgeuse's bow shock is very young and is unlikely to have reached a steady state. The circular nature of the bow shock shell is consistent with this conclusion. Thus, our results suggest that Betelgeuse only entered the red supergiant phase recently.

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RED SUPERGIANTS AS POTENTIAL TYPE IIn SUPERNOVA PROGENITORS: SPATIALLY RESOLVED 4.6 μm CO EMISSION AROUND VY CMa AND BETELGEUSE

Cited by 181 publications

References 126 publications

Grids of stellar models with rotation

Grids of stellar models with rotation

The close circumstellar environment of Betelgeuse

3D simulations of Betelgeuse’s bow shock

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