CARMA CO(<i>J</i>= 2 – 1) OBSERVATIONS OF THE CIRCUMSTELLAR ENVELOPE OF BETELGEUSE

O’Gorman, Eamon; Harper, G. M.; Brown, J. M.; Brown, Alexander; Redfield, Seth; Richter, Matthew J.; Requeña-Torres, M. A.

doi:10.1088/0004-6256/144/2/36

Cited by 18 publications

(9 citation statements)

References 35 publications

(70 reference statements)

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“…However, there is no theoretical model available to explain these observations. The CO J = 2 − 1 transition in the CSE of Betelgeuse was observed with CARMA (O'Gorman et al 2012). Their restoring beam and spectral resolution were similar to our NOEMA observations of µ Cep.…”

Section: Comparison With Other Nearby Red Supergiant Starssupporting

confidence: 85%

NOEMA maps the CO J = 2 − 1 environment of the red supergiant $\mu$ Cep★

Montargès

Homan

Keller

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Red supergiant stars are surrounded by a gaseous and dusty circumstellar environment created by their mass loss which spreads heavy elements into the interstellar medium. The structure and the dynamics of this envelope are crucial to understand the processes driving the red supergiant mass loss and the shaping of the pre-supernova ejecta. We have observed the emission from the CO J = 2 − 1 line from the red supergiant star µ Cep with the NOEMA interferometer. In the line the synthesized beam was 0.92 × 0.72 arcsec (590 × 462 au at 641 pc). The continuum map shows only the unresolved contribution of the free-free emission of the star chromosphere. The continuum-subtracted channel maps reveal a very inhomogeneous and clumpy circumstellar environment. In particular, we detected a bright CO clump, as bright as the central source in the line, at 1.80 arcsec south-west from the star, in the blue channel maps. After a deprojection of the radial velocity assuming two different constant wind velocities, the observations were modelled using the 3D radiative transfer code lime to derive the characteristics of the different structures. We determine that the gaseous clumps observed around µ Cep are responsible for a mass loss rate of (4.9 ± 1.0) × 10 −7 M yr −1 , in addition to a spatially unresolved wind component with an estimated mass-loss rate of 2.0 × 10 −6 M yr −1 . Therefore, the clumps have a significant role in µ Cep's mass loss (≥ 25%). We cannot exclude that the unresolved central outflow may be made of smaller unresolved clumps.

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Section: Comparison With Other Nearby Red Supergiant Starssupporting

confidence: 85%

NOEMA maps the CO J = 2 − 1 environment of the red supergiant $\mu$ Cep★

Montargès

Homan

Keller

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…The 2019-2020 extreme dimming of Betelgeuse seems the only confirmed example for this star over the previous century. Previous observations of the circumstellar environment of Betelgeuse 8,[34][35][36][37] show a very inhomogeneous environment embedded in a smoother matrix. This may confirm that Betelgeuse and possibly other RSG experience two modes of mass loss 8,38,39 : a smooth homogeneous radial outflow mainly consisting of gas with at most partial dust nucleation farther away from the star; and an episodic localised ejection of clumps of gas where conditions are favorable for efficient dust formation while still close to the photosphere.…”

Section: /19mentioning

confidence: 99%

A dusty veil shading Betelgeuse during its Great Dimming

Montargès

Cannon

Lagadec

et al. 2021

Nature

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Red supergiants represent the most common final stage of the evolution of stars with initial masses between 8 and 30-35 times the mass of the Sun 1 . During this phase of lifetime lasting ≈ 10 5 yrs 1 , they experience substantial mass loss of unknown mechanism 2 . This mass loss can affect their evolutionary path, collapse, future supernova light curve 3 , and ultimate fate as a neutron star or a black hole 4 . From November 2019 to March 2020, the second closest red supergiant (RSG, 222 +48 −34 pc 5, 6 ) Betelgeuse experienced a historic dimming of its visible brightness, witnessed worldwide. Usually between 0.1 and 1.0 mag, it went down to 1.614 ± 0.008 mag around 7-13 February 2020 7 . Here we report high angular resolution observations showing that the southern hemisphere of the star was ten times darker than usual in the visible. Observations and modeling support the scenario of a dust clump recently formed in the vicinity of the star due to a local temperature decrease in a cool patch appearing on the photosphere. The directly imaged brightness variations of Betelgeuse evolved on a timescale of weeks. This event suggests that an inhomogeneous component of red supergiant mass loss 8 is linked to a very contrasted and rapidly changing photosphere.

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“…However, the strengths of optical TiO band heads may also be affected by temperature effects from the chromosphere (Lobel & Dupree 2000). Assuming the longer wavelength radio emission originates in the more extended atmosphere, one would expect a delay of ∼3-6 yr for a disturbance to propagate out from the photosphere to these radio formation regions, assuming a velocity of 10 km s −1 (e.g., O'Gorman et al 2012). Clearly, this is too long a timescale in comparison to the similar timescales between both the optical and the radio flux density variability that is evident in Fig.…”

Section: Radio Flux Density Versus Optical Photometrymentioning

confidence: 99%

Temporal evolution of the size and temperature of Betelgeuse’s extended atmosphere

O’Gorman

Harper

Brown

et al. 2015

A&A

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Spatially resolved multi-wavelength centimeter continuum observations of cool evolved stars can not only constrain the morphology of the radio emitting regions, but can also directly probe the mean gas temperature at various depths of the star's extended atmosphere. Here, we use the Very Large Array (VLA) in the A configuration with the Pie Town (PT) Very Long Baseline Array (VLBA) antenna to spatially resolve the extended atmosphere of Betelgeuse over multiple epochs at 0.7, 1.3, 2.0, 3.5, and 6.1 cm. The extended atmosphere deviates from circular symmetry at all wavelengths while at some epochs we find possible evidence for small pockets of gas significantly cooler than the mean global temperature. We find no evidence for the recently reported e-MERLIN radio hotspots in any of our multi-epoch VLA/PT data, despite having sufficient spatial resolution and sensitivity at short wavelengths, and conclude that these radio hotspots are most likely interferometric artefacts. The mean gas temperature of the extended atmosphere has a typical value of 3000 K at 2 R and decreases to 1800 K at 6 R , in broad agreement with the findings of the single epoch study from Lim et al. (1998, Nature, 392, 575). The overall temperature profile of the extended atmosphere between 2 R r 6 R can be described by a power law of the form T gas (r) ∝ r −0.6 , with temporal variability of a few 100 K evident at some epochs. Finally, we present over 12 yr of V band photometry, part of which overlaps our multi-epoch radio data. We find a correlation between the fractional flux density variability at V band with most radio wavelengths. This correlation is likely due to shock waves induced by stellar pulsations, which heat the inner atmosphere and ionize the more extended atmosphere through radiative means. Stellar pulsations may play an important role in exciting Betelgeuse's extended atmosphere.

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CARMA CO(J= 2 – 1) OBSERVATIONS OF THE CIRCUMSTELLAR ENVELOPE OF BETELGEUSE

Cited by 18 publications

References 35 publications

NOEMA maps the CO J = 2 − 1 environment of the red supergiant $\mu$ Cep★

NOEMA maps the CO J = 2 − 1 environment of the red supergiant $\mu$ Cep★

A dusty veil shading Betelgeuse during its Great Dimming

Temporal evolution of the size and temperature of Betelgeuse’s extended atmosphere

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