3D simulations of Betelgeuse’s bow shock

Mohamed, S.; Mackey, Jonathan; Langer, N.

doi:10.1051/0004-6361/201118002

Cited by 77 publications

(74 citation statements)

References 52 publications

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“…As a result, the Kelvin-Helmholtz instabilities are much greater, leading to a large-scale instability that changes the shape of the entire bow shock. This is contrary to the results of Mohamed et al (2012), who obtained a smooth bow shock for similar input parameters. This difference may be the result of a different numerical treatment (grid versus SPH), but may also result from the total timescale of the Fig.…”

Section: Warm Ambient Mediumcontrasting

confidence: 99%

“…4.2.1 yield a mass in the arcs of ∼0.1 M (including 90% CSM and 10% ISM material). According to Mohamed et al (2012), the observed low mass in the arcs might indicate that the bow shock created by the RSG wind has a very young age, of the order of 20 000 yrs, and may not yet have reached a steady state. But, the existence of (non-homogeneous) clumps in the inner wind travelling all the way to the bow shock region might also explain the low mass in the arcs as derived from the Herschel images.…”

Section: Mass Of the Arcs And Linear Barmentioning

confidence: 99%

“…Therefore, whereas the ambient medium is kept at a minimum temperature of 8000 K, the stellar wind, which is protected from UV-radiation by the ionized gas of the bow shock, has a minimum temperature of 100 K. -The fourth simulation (D) has the same ambient medium temperature as simulation C, but with lower ambient medium density (5 × 10 −25 g cm −3 ) and higher space velocity (v = 72.5 km s −1 ). This simulation was added to compare our results with the recent hydrodynamical models of Mohamed et al (2012). -For the fifth simulation (E), as for the first and second, we set the minimum temperature to 100 K throughout the entire domain.…”

Section: Constraints From Hydrodynamical Modellingmentioning

confidence: 99%

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The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed byHerschel

Decin

Cox

Royer

et al. 2012

A&A

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Context. The interaction between stellar winds and the interstellar medium (ISM) can create complex bow shocks. The photometers on board the Herschel Space Observatory are ideally suited to studying the morphologies of these bow shocks. Aims. We aim to study the circumstellar environment and wind-ISM interaction of the nearest red supergiant, Betelgeuse. Methods. Herschel PACS images at 70, 100, and 160 μm and SPIRE images at 250, 350, and 500 μm were obtained by scanning the region around Betelgeuse. These data were complemented with ultraviolet GALEX data, near-infrared WISE data, and radio 21 cm GALFA-HI data. The observational properties of the bow shock structure were deduced from the data and compared with hydrodynamical simulations. Results. The infrared Herschel images of the environment around Betelgeuse are spectacular, showing the occurrence of multiple arcs at ∼6-7 from the central target and the presence of a linear bar at ∼9 . Remarkably, no large-scale instabilities are seen in the outer arcs and linear bar. The dust temperature in the outer arcs varies between 40 and 140 K, with the linear bar having the same colour temperature as the arcs. The inner envelope shows clear evidence of a non-homogeneous clumpy structure (beyond 15 ), probably related to the giant convection cells of the outer atmosphere. The non-homogeneous distribution of the material even persists until the collision with the ISM. A strong variation in brightness of the inner clumps at a radius of ∼2 suggests a drastic change in mean gas and dust density ∼32 000 yr ago. Using hydrodynamical simulations, we try to explain the observed morphology of the bow shock around Betelgeuse. Conclusions. Different hypotheses, based on observational and theoretical constraints, are formulated to explain the origin of the multiple arcs and the linear bar and the fact that no large-scale instabilities are visible in the bow shock region. We infer that the two main ingredients for explaining these phenomena are a non-homogeneous mass-loss process and the influence of the Galactic magnetic field. The hydrodynamical simulations show that a warm interstellar medium, reflecting a warm neutral or partially ionized medium, or a higher temperature in the shocked wind also prevent the growth of strong instabilities. The linear bar is probably an interstellar structure illuminated by Betelgeuse itself.

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Section: Warm Ambient Mediumcontrasting

confidence: 99%

Section: Mass Of the Arcs And Linear Barmentioning

confidence: 99%

Section: Constraints From Hydrodynamical Modellingmentioning

confidence: 99%

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The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed byHerschel

Decin

Cox

Royer

et al. 2012

A&A

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“…At these phases, massive stars may undergo rapid transitions from red to blue supergiants and vice versa in the Hertzprung-Russell diagram, and the stellar wind velocities also change rapidly. Mohamed et al (2012) found that the bow shock formed by Betelgeuse is still young (<30 kyr). The total kinetic power is rather low, but the star is relatively close and a possible low X-ray luminosity can still be detectable.…”

Section: Betelgeusementioning

confidence: 98%

Modeling nonthermal emission from stellar bow shocks

Pereira

López‐Santiago

Miceli

et al. 2016

A&A

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Context. Runaway O-and early B-type stars passing through the interstellar medium at supersonic velocities and characterized by strong stellar winds may produce bow shocks that can serve as particle acceleration sites. Previous theoretical models predict the production of high-energy photons by nonthermal radiative processes, but their efficiency is still debated. Aims. We aim to test and explain the possibility of emission from the bow shocks formed by runaway stars traveling through the interstellar medium by using previous theoretical models. Methods. We applied our model to AE Aurigae, the first reported star with an X-ray detected bow shock, to BD+43 3654, in which the observations failed in detecting high-energy emission, and to the transition phase of a supergiant star in the late stages of its life. Results. From our analysis, we confirm that the X-ray emission from the bow shock produced by AE Aurigae can be explained by inverse Compton processes involving the infrared photons of the heated dust. We also predict low high-energy flux emission from the bow shock produced by BD+43 3654, and the possibility of high-energy emission from the bow shock formed by a supergiant star during the transition phase from blue to red supergiant. Conclusions. Bow shocks formed by different types of runaway stars are revealed as a new possible source of high-energy photons in our neighborhood.

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“…Subsequent attempts by van Marle et al (2011) and Decin et al (2012) to model the bow shock of α-Orionis showed large instabilities that would be observable with Herschel, if they exist. The absence of instabilities has been explained by Mohamed et al (2012) and Appendix A and associated movies are available in electronic form at http://www.aanda.org Mackey et al (2012) as evidence that the bow shock is still in an early stage of formation and that the instabilities have not yet had time to develop.…”

Section: Introductionmentioning

confidence: 99%

Can the magnetic field in the Orion arm inhibit the growth of instabilities in the bow shock of Betelgeuse?

Marle¹,

Decin²,

Méliani³

2014

A&A

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Context. Many evolved stars travel through space at supersonic velocities, which leads to the formation of bow shocks ahead of the star where the stellar wind collides with the interstellar medium (ISM). Herschel observations of the bow shock of α-Orionis show that the shock is almost free of instabilities, despite being, at least in theory, subject to both Kelvin-Helmholtz and Rayleigh-Taylor instabilities. Aims. A possible explanation for the lack of instabilities lies in the presence of an interstellar magnetic field. We wish to investigate whether the magnetic field of the ISM in the Orion arm can inhibit the growth of instabilities in the bow shock of α-Orionis. Methods. We used the code MPI-AMRVAC to make magneto-hydrodynamic simulations of a circumstellar bow shock, using the wind parameters derived for α-Orionis and interstellar magnetic field strengths of B = 1.4, 3.0, and 5.0 µG, which fall within the boundaries of the observed magnetic field strength in the Orion arm of the Milky Way. Results. Our results show that even a relatively weak magnetic field in the ISM can suppress the growth of Rayleigh-Taylor and Kelvin-Helmholtz instabilities, which occur along the contact discontinuity between the shocked wind and the shocked ISM. Conclusions. The presence of even a weak magnetic field in the ISM effectively inhibits the growth of instabilities in the bow shock. This may explain the absence of such instabilities in the Herschel observations of α-Orionis.

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3D simulations of Betelgeuse’s bow shock

Cited by 77 publications

References 52 publications

The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed byHerschel

The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed byHerschel

Modeling nonthermal emission from stellar bow shocks

Can the magnetic field in the Orion arm inhibit the growth of instabilities in the bow shock of Betelgeuse?

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