Wind nebulae and supernova remnants of very massive stars

ABSTRACT A very small fraction of (runaway) massive stars have masses exceeding $60\!-\!70\, \rm M_{\odot }$ and are predicted to evolve as luminous blue variable and Wolf–Rayet stars before ending their lives as core-collapse supernovae. Our 2D axisymmetric hydrodynamical simulations explore how a fast wind ($2000\, \rm km\, \rm s^{-1}$) and high mass-loss rate ($10^{-5}\, \rm M_{\odot }\, \rm yr^{-1}$) can impact the morphology of the circumstellar medium. It is shaped as 100 pc-scale wind nebula that can be pierced by the driving star when it supersonically moves with velocity $20\!-\!40\, \rm km\, \rm s^{-1}$ through the interstellar medium (ISM) in the Galactic plane. The motion of such runaway stars displaces the position of the supernova explosion out of their bow shock nebula, imposing asymmetries to the eventual shock wave expansion and engendering Cygnus-loop-like supernova remnants. We conclude that the size (up to more than $200\, \rm pc$) of the filamentary wind cavity in which the chemically enriched supernova ejecta expand, mixing efficiently the wind and ISM materials by at least $10{{\ \rm per\ cent}}$ in number density, can be used as a tracer of the runaway nature of the very massive progenitors of such $0.1\, \rm Myr$ old remnants. Our results motivate further observational campaigns devoted to the bow shock of the very massive stars BD+43°3654 and to the close surroundings of the synchrotron-emitting Wolf–Rayet shell G2.4+1.4.

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Non-thermal radio supernova remnants of exiled Wolf–Rayet stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab452 ◽

2021 ◽

Vol 502 (4) ◽

pp. 5340-5355

Author(s):

D M-A Meyer ◽

M Pohl ◽

M Petrov ◽

L Oskinova

Keyword(s):

Magnetic Field ◽

Supernova Remnants ◽

Supernova Explosion ◽

High Mass ◽

Mixing Efficiency ◽

Thermal Radio ◽

Thermal Radio Emission ◽

Characteristic Features ◽

Hydrodynamical Simulations ◽

Circumstellar Medium

ABSTRACT A signification fraction of Galactic massive stars (${\ge}8\, \rm M_{\odot }$) are ejected from their parent cluster and supersonically sail away through the interstellar medium (ISM). The winds of these fast-moving stars blow asymmetric bubbles thus creating a circumstellar environment in which stars eventually die with a supernova explosion. The morphology of the resulting remnant is largely governed by the circumstellar medium of the defunct progenitor star. In this paper, we present 2D magneto-hydrodynamical simulations investigating the effect of the ISM magnetic field on the shape of the supernova remnants of a $35\, \mathrm{M}_{\odot }$ star evolving through a Wolf–Rayet phase and running with velocity 20 and $40\, \rm km\, \rm s^{-1}$, respectively. A $7\, \mu \rm G$ ambient magnetic field is sufficient to modify the properties of the expanding supernova shock front and in particular to prevent the formation of filamentary structures. Prior to the supernova explosion, the compressed magnetic field in the circumstellar medium stabilizes the wind/ISM contact discontinuity in the tail of the wind bubble. A consequence is a reduced mixing efficiency of ejecta and wind materials in the inner region of the remnant, where the supernova shock wave propagates. Radiative transfer calculations for synchrotron emission reveal that the non-thermal radio emission has characteristic features reflecting the asymmetry of exiled core-collapse supernova remnants from Wolf–Rayet progenitors. Our models are qualitatively consistent with the radio appearance of several remnants of high-mass progenitors, namely the bilateral G296.5+10.0 and the shell-type remnants CTB109 and Kes 17, respectively.

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On the ring nebulae around runaway Wolf–Rayet stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1700 ◽

2020 ◽

Vol 496 (3) ◽

pp. 3906-3911

Author(s):

D M-A Meyer ◽

L M Oskinova ◽

M Pohl ◽

M Petrov

Keyword(s):

High Latitude ◽

Stellar Wind ◽

Near Infrared ◽

Moving Objects ◽

Galactic Plane ◽

Massive Stars ◽

Ambient Medium ◽

Bow Shock ◽

Fast Wind ◽

Bow Shocks

ABSTRACT Wolf–Rayet stars are advanced evolutionary stages of massive stars. Despite their large mass-loss rates and high wind velocities, none of them displays a bow shock, although a fraction of them are classified as runaway. Our 2.5-D numerical simulations of circumstellar matter around a $60\mbox{-}\rm M_{\odot }$ runaway star show that the fast Wolf–Rayet stellar wind is released into a wind-blown cavity filled with various shocks and discontinuities generated throughout the preceding evolutionary phases. The resulting fast-wind–slow-wind interaction leads to the formation of spherical shells of swept-up dusty material similar to those observed in the near-infrared at $24\, \rm \mu \rm m$ with Spitzer, which appear to be comoving with the runaway massive stars, regardless of their proper motion and/or the properties of the local ambient medium. We interpret bright infrared rings around runaway Wolf–Rayet stars in the Galactic plane as an indication of their very high initial masses and complex evolutionary history. Stellar-wind bow shocks become faint as stars run in diluted media, therefore our results explain the absence of bow shocks detected around Galactic Wolf–Rayet stars, such as the high-latitude, very fast-moving objects WR71, WR124 and WR148. Our results show that the absence of a bow shock is consistent with the runaway nature of some Wolf–Rayet stars. This questions the in situ star formation scenario of high-latitude Wolf–Rayet stars in favour of dynamical ejection from birth sites in the Galactic plane.

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Formation of the SMC WO+O binary AB8

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318008128 ◽

2018 ◽

Vol 14 (S346) ◽

pp. 78-82

Author(s):

Chen Wang ◽

Norbert Langer ◽

Götz Gräfener ◽

Pablo Marchant

Keyword(s):

Binary Systems ◽

Mass Loss Rate ◽

Vital Role ◽

Least Square ◽

High Mass ◽

Stellar Winds ◽

High Mass Loss ◽

Low Metallicity ◽

Binary Evolution ◽

Oxygen Ratio

AbstractWolf-Rayet (WR) stars are stripped stellar cores that form through strong stellar wind or binary mass transfer. It is proposed that binary evolution plays a vital role in the formation of WR stars in low metallicity environments due to the metallicity dependance of stellar winds. However observations indicate a similar binary fraction of WR stars in the Small Magellanic Cloud (SMC) compared to the Milky Way. There are twelve WR stars in the SMC and five of them are members of binary systems. One of them (SMC AB8) harbors a WO type star. In this work we explore possible formation channels of this binary. We use the MESA code to compute large grids of binary evolution models, and then use least square fitting to compare our models with the observations. In order to reproduce the key properties of SMC AB8, we require efficient semiconvection to produce a sufficiently large convective core, as well as a longer He-burning lifetime. We also need a high mass loss rate during the WN stage to assist the removal of the outer envelope. In this way, we can reproduce the observed properties of AB8, except for the surface carbon to oxygen ratio, which requires further investigation.

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The B[e] stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100004358 ◽

1989 ◽

Vol 113 ◽

pp. 117-120

Author(s):

F.-J. Zickgraf

Keyword(s):

Physical Properties ◽

Stellar Wind ◽

Main Sequence ◽

Massive Stars ◽

High Mass ◽

Sequence Evolution ◽

Two Component ◽

Show Evidence ◽

High Mass Loss ◽

General Appearance

AbstractB[e] supergiants show evidence for a non-spherical two-component stellar wind. The general appearance and the physical properties of the suggested disk-like configuration are discussed. The high mass-loss rates, the surprisingly large number and the location in the H-R diagram make these stars important for the understanding of the post-main-sequence evolution of massive stars.

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Observational connections between LBV’s and other stars, with emphasis on Wolf-Rayet stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100004498 ◽

1989 ◽

Vol 113 ◽

pp. 229-240

Author(s):

A. F. J. Moffat ◽

L. Drissen ◽

C. Robert

Keyword(s):

Mass Loss ◽

Massive Stars ◽

Underlying Mechanism ◽

High Mass ◽

Strong Line ◽

Essential Step ◽

High Mass Loss ◽

Loss Rates ◽

R Domain

Abstract.We suggest that the LBV mechanism is an essential step to “force” massive stars (M(ZAMS) ≥ 40M⊙) to finally enter the Wolf-Rayet (W-R) domain in the Hertzsprung-Russel diagram (HRD). Just as massive supergiants showincreasingvariability as theyapproachthe Humphreys-Davidson (H-D)instability limit (horizontally in the HRD diagram), so the W-R stars showdecreasingvariability as theyrecede fromthe H-D limit (at first horizontally into the WNL domain, then, with their high mass loss rates, plunging irreversably downwards as ever hotter, smaller and fainter, strong-line W-R stars). Among the W-R stars, the luminous WNL subtypes (especially WN8) are the most variable, probably as a consequence of blob ejection in the wind. The underlying mechanism which triggers this ejection is possibly related to wind instabilities and may thus be quite different from the source of variability in luminous supergiants or LBV’s in quiescence, where photospheric effects dominate.

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Modeling of hydrodynamic processes within high-mass X-ray binaries

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319000024 ◽

2018 ◽

Vol 14 (S346) ◽

pp. 197-201

Author(s):

Petr Kurfürst ◽

Jiří Krtička

Keyword(s):

Mass Loss Rate ◽

Compact Object ◽

Supernova Explosion ◽

High Mass ◽

Be Stars ◽

X Ray ◽

Hydrodynamic Processes ◽

Hydrodynamic Structure ◽

X Ray Binaries ◽

Circumstellar Environment

AbstractHigh-mass X-ray binaries belong to the brightest objects in the X-ray sky. They usually consist of a massive O or B star or a blue supergiant while the compact X-ray emitting component is a neutron star (NS) or a black hole. Intensive matter accretion onto the compact object can take place through different mechanisms: wind accretion, Roche-lobe overflow, or circumstellar disk. In our multi-dimensional models we perform numerical simulations of the accretion of matter onto a compact companion in case of Be/X-ray binaries. Using Bondi-Hoyle-Littleton approximation, we estimate the NS accretion rate. We determine the Be/X-ray binary disk hydrodynamic structure and compare its deviation from isolated Be stars’ disk. From the rate and morphology of the accretion flow and the X-ray luminosity we improve the estimate of the disk mass-loss rate. We also study the behavior of a binary system undergoing a supernova explosion, assuming a blue supergiant progenitor with an aspherical circumstellar environment.

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An ALMA view of SO and SO2 around oxygen-rich AGB stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa693 ◽

2020 ◽

Vol 494 (1) ◽

pp. 1323-1347 ◽

Cited By ~ 3

Author(s):

T Danilovich ◽

A M S Richards ◽

L Decin ◽

M Van de Sande ◽

C A Gottlieb

Keyword(s):

Mass Loss ◽

Loss Rate ◽

Mass Loss Rate ◽

Energy Levels ◽

High Mass ◽

High Angular Resolution ◽

Circumstellar Envelope ◽

Agb Stars ◽

Abundance Distribution ◽

High Mass Loss

ABSTRACT We present and analyse SO and SO2, recently observed with high angular resolution and sensitivity in a spectral line survey with ALMA, for two oxygen-rich AGB stars: the low mass-loss rate R Dor and high mass-loss rate IK Tau. We analyse 8 lines of SO detected towards both stars, 78 lines of SO2 detected towards R Dor, and 52 lines of SO2 detected towards IK Tau. We detect several lines of 34SO, 33SO, and 34SO2 towards both stars, and tentatively S18O towards R Dor, and hence derive isotopic ratios for these species. The spatially resolved observations show us that the two sulphur oxides are co-located towards R Dor and trace out the same wind structures in the circumstellar envelope. Much of the emission is well reproduced with a Gaussian abundance distribution spatially centred on the star. Emission from the higher energy levels of SO and SO2 towards R Dor provides evidence in support of a rotating inner region of gas identified in earlier work. The new observations allow us to refine the abundance distribution of SO in IK Tau derived from prior observations with single antennas, and confirm that the distribution is shell like with the peak in the fractional abundance not centred on the star. The confirmation of different types of SO abundance distributions will help fine-tune chemical models and allows for an additional method to discriminate between low and high mass-loss rates for oxygen-rich AGB stars.

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Luminous Blue Variables, cool hypergiants and some impostors in the H-R diagram

Symposium - International Astronomical Union ◽

10.1017/s0074180900211625 ◽

2003 ◽

Vol 212 ◽

pp. 38-46

Author(s):

Roberta M. Humphreys

Keyword(s):

Magnetic Fields ◽

Mass Loss ◽

Surface Activity ◽

Massive Star ◽

Massive Stars ◽

High Mass ◽

Luminous Blue Variables ◽

Star Evolution ◽

High Mass Loss ◽

Massive Star Evolution

Current observations of the S Dor/LBVs and candidates and the implications for their important role in massive star evolution are reviewed. Recent observations of the cool hypergiants are altering our ideas about their evolutionary state, their atmospheres and winds, and the possible mechanisms for their asymmetric high mass loss episodes which may involve surface activity and magnetic fields. Recent results for IRC+10420, ρ Cas and VY CMa are highlighted. S Dor/LBVs in eruption, and the cool hypergiants in their high mass loss phases with their optically thick winds are not what their apparent spectra and temperatures imply; they are then ‘impostors’ on the H-R diagram. The importance of the very most massive stars, like η Carinae and the ‘supernovae impostors’ are also discussed.

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Close binary models for Luminous Blue Variable stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100004449 ◽

1989 ◽

Vol 113 ◽

pp. 185-194

Author(s):

J. S. Gallagher

Keyword(s):

Mass Loss ◽

Binary Stars ◽

Mass Loss Rate ◽

Variable Stars ◽

High Mass ◽

Close Binary ◽

Close Binaries ◽

System A ◽

Close Binary Stars ◽

High Mass Loss

AbstractThe evolution of massive close binary stars inevitably involves mass exchange between the two stellar components as well as mass loss from the system. A combination of these two processes could produce the stellar wind-modulated behavior seen in LB Vs. The possibility that LBVs are powered by accretion is examined, and does not appear to be a satisfactory general model. Instead, identification of LBVs with close binaries in high mass-loss rate or common envelope evolutionary phases shows promise.

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