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201 Publications visible to you, out of a total of 201
Common-envelope evolution with an asymptotic giant branch star

Abstract

Not specified

Authors: Christian Sand, Sebastian T. Ohlmann, Fabian R. N. Schneider, Rüdiger Pakmor, Friedrich K. Röpke

Date Published: 1st Dec 2020

Publication Type: Journal

HOLISMOKES. I. Highly Optimised Lensing Investigations of Supernovae, Microlensing Objects, and Kinematics of Ellipticals and Spirals

Abstract

Not specified

Authors: S. H. Suyu, S. Huber, R. Cañameras, M. Kromer, S. Schuldt, S. Taubenberger, A. Yıldırım, V. Bonvin, J. H. H. Chan, F. Courbin, U. Nöbauer, S. A. Sim, D. Sluse

Date Published: 1st Dec 2020

Publication Type: Journal

VizieR Online Data Catalog: OB stars TESS phot. & high-resolution spectroscopy (Bowman+, 2020)

Abstract

Not specified

Authors: D. M. Bowman, S. Burssens, S. Simon-Diaz, P. V. F. Edelmann, T. M. Rogers, L. Horst, F. K. Ropke, C. Aerts

Date Published: 1st Oct 2020

Publication Type: Journal

Formation of sdB-stars via common envelope ejection by substellar companions

Abstract

Not specified

Authors: M. Kramer, F. R. N. Schneider, S. T. Ohlmann, S. Geier, V. Schaffenroth, R. Pakmor, F. K. Röpke

Date Published: 1st Oct 2020

Publication Type: Journal

Fully compressible simulations of waves and core convection in main-sequence stars

Abstract (Expand)

Context. Recent, nonlinear simulations of wave generation and propagation in full-star models have been carried out in the anelastic approximation using spectral methods. Although it makes long time … steps possible, this approach excludes the physics of sound waves completely and requires rather high artificial viscosity and thermal diffusivity for numerical stability. A direct comparison with observations is thus limited. Aims. We explore the capabilities of our compressible multidimensional Seven-League Hydro (SLH) code to simulate stellar oscillations. Methods. We compare some fundamental properties of internal gravity and pressure waves in 2D SLH simulations to linear wave theory using two test cases: (1) an interval gravity wave packet in the Boussinesq limit and (2) a realistic 3 M⊙ stellar model with a convective core and a radiative envelope. Oscillation properties of the stellar model are also discussed in the context of observations. Results. Our tests show that specialized low-Mach techniques are necessary when simulating oscillations in stellar interiors. Basic properties of internal gravity and pressure waves in our simulations are in good agreement with linear wave theory. As compared to anelastic simulations of the same stellar model, we can follow internal gravity waves of much lower frequencies. The temporal frequency spectra of velocity and temperature are flat and compatible with the observed spectra of massive stars. Conclusion. The low-Mach compressible approach to hydrodynamical simulations of stellar oscillations is promising. Our simulations are less dissipative and require less luminosity boosting than comparable spectral simulations. The fully-compressible approach allows for the coupling of gravity and pressure waves in the outer convective envelopes of evolved stars to be studied in the future.

Authors: L. Horst, P. V. F. Edelmann, R. Andrássy, F. K. Röpke, D. M. Bowman, C. Aerts, R. P. Ratnasingam

Date Published: 1st Sep 2020

Publication Type: Journal

Photometric detection of internal gravity waves in upper main-sequence stars

Abstract (Expand)

Context. Massive stars are predicted to excite internal gravity waves (IGWs) by turbulent core convection and from turbulent pressure fluctuations in their near-surface layers. These IGWs are extremely … efficient at transporting angular momentum and chemical species within stellar interiors, but they remain largely unconstrained observationally. Aims. We aim to characterise the photometric detection of IGWs across a large number of O and early-B stars in the Hertzsprung–Russell diagram, and explain the ubiquitous detection of stochastic variability in the photospheres of massive stars. Methods. We combined high-precision time-series photometry from the NASA Transiting Exoplanet Survey Satellite with high-resolution ground-based spectroscopy of 70 stars with spectral types O and B to probe the relationship between the photometric signatures of IGWs and parameters such as spectroscopic mass, luminosity, and macroturbulence. Results. A relationship is found between the location of a star in the spectroscopic Hertzsprung–Russell diagram and the amplitudes and frequencies of stochastic photometric variability in the light curves of massive stars. Furthermore, the properties of the stochastic variability are statistically correlated with macroturbulent velocity broadening in the spectral lines of massive stars. Conclusions. The common ensemble morphology for the stochastic low-frequency variability detected in space photometry and its relationship to macroturbulence is strong evidence for IGWs in massive stars, since these types of waves are unique in providing the dominant tangential velocity field required to explain the observed spectroscopy.

Authors: D. M. Bowman, S. Burssens, S. Simón-Díaz, P. V. F. Edelmann, T. M. Rogers, L. Horst, F. K. Röpke, C. Aerts

Date Published: 1st Aug 2020

Publication Type: Journal

Polluting the Pair-instability Mass Gap for Binary Black Holes through Super-Eddington Accretion in Isolated Binaries

Abstract (Expand)

The theory for single stellar evolution predicts a gap in the mass distribution of black holes (BHs) between approximately 45 and 130 $\,{M}_{\odot }$, the so-called "pair-instability mass gap." … We examine whether BHs can pollute the gap after accreting from a stellar companion. To this end, we simulate the evolution of isolated binaries using a population synthesis code, where we allow for super-Eddington accretion. Under our most extreme assumptions, we find that at most about 2% of all merging binary BH systems contains a BH with a mass in the pair-instability mass gap, and we find that less than 0.5% of the merging systems has a total mass larger than 90 $\,{M}_{\odot }$. We find no merging binary BH systems with a total mass exceeding 100 $\,{M}_{\odot }$. We compare our results to predictions from several dynamical pathways to pair-instability mass gap events and discuss the distinguishable features. We conclude that the classical isolated binary formation scenario will not significantly contribute to the pollution of the pair-instability mass gap. The robustness of the predicted mass gap for the isolated binary channel is promising for the prospective of placing constraints on (i) the relative contribution of different formation channels, (ii) the physics of the progenitors including nuclear reaction rates, and, tentatively, (iii) the Hubble parameter.

Authors: L. A. C. van Son, S. E. De Mink, F. S. Broekgaarden, M. Renzo, S. Justham, E. Laplace, J. Morán-Fraile, D. D. Hendriks, R. Farmer

Date Published: 1st Jul 2020

Publication Type: Journal

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