Article
Astronomy & Astrophysics
R. Ricci, E. Troja, G. Bruni, T. Matsumoto, L. Piro, B. O'Connor, T. Piran, N. Navaieelavasani, A. Corsi, B. Giacomazzo, M. H. Wieringa
Summary: Neutron star mergers create fast-moving ejecta that interact with surrounding medium, potentially producing isotropic radio remnants; Late-time radio observations of short duration gamma-ray bursts help constrain the model, ruling out the presence of a powerful magnetar as a merger remnant for certain ejecta mass ranges.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Peter B. Rau, Ira Wasserman
Summary: We investigated the stability of Hall magnetohydrodynamic with strong magnetic fields, focusing on the importance of Landau quantization of electrons. It was found that the strong-field Hall modes can become unstable due to the dependence of the differential magnetic susceptibility on magnetic field strength. The hydrodynamic instability, originating from thermodynamics and stabilized by magnetic domain formation, was analyzed using linear perturbation theory.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Peter B. Rau, Ira Wasserman
Summary: This study examines the magnetohydrodynamic stability of neutron star core matter under a strong magnetic field, finding that the magnetized fluid is unstable to a magnetosonic-type instability with growth times of the order of 10(-3) s under sufficiently strong magnetic field conditions. This instability is triggered by sharp changes in the second-order field derivative of the Lagrangian, influenced by Landau quantization of fermions and quantum electrodynamical effects.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Hao-Jui Kuan, Arthur G. Suvorov, Kostas D. Kokkotas
Summary: The study investigates the causes of precursor flares in merging quasi-circular binaries and finds that tidal forces resonantly excite quasi-normal modes in stars, leading to a rapid increase in amplitude and ultimately triggering crustal failure.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Swapnil Shankar, Philipp Mosta, Jennifer Barnes, Paul C. Duffell, Daniel Kasen
Summary: The study suggests that some high-energy SNe Ic-bl may be driven by jets from proto-magnetars, with a potential connection to GRBs. The results show that central engines with smaller opening angles are more likely to form GRBs, while those with larger opening angles are less likely to form GRBs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Yasufumi Kojima, Shota Kisaka, Kotaro Fujisawa
Summary: We investigated the magneto-elastic equilibrium and magnetic energy stored through elastic forces in the crust of a neutron star. Our findings suggest that the magnetic elastic force can control the magnetic field and reduce the restrictions on its strength and geometry. Furthermore, our numerical calculations demonstrated that even for weaker magnetic field strengths, the neutron star's crust can store a significant amount of magnetic energy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
M. Bugli, J. Guilet, M. Obergaulinger
Summary: Magnetic fields play a crucial role in core-collapse supernovae, with more complex field structures beyond aligned dipoles potentially leading to weaker explosions but more efficient extraction of rotational energy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
A. G. Suvorov, K. D. Kokkotas
Summary: This study found that 16 out of 25 magnetars associated with X-ray light curves exhibiting a plateau show evidence of precession. The analysis of the light curves allows for an independent measure of the extent of star deformation and distribution of magnetic-energy ratios.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
J. P. Hu, F. Y. Wang, Z. G. Dai
Summary: This paper investigates gamma-ray bursts (GRBs) with plateau phases in X-ray afterglow and finds that selecting GRBs from the same physical mechanism is crucial for cosmological purposes. The study calibrates the correlations between plateau luminosity and end time of plateau to constrain ΛCDM and w(z) = w(0) models. The results support the ΛCDM model and highlight the importance of careful selection of GRBs for cosmological studies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Michail Damoulakis, Rodolfo Barniol Duran, Dimitrios Giannios
Summary: Despite debates on the nature of the compact object at the central engine and the mechanism behind the prompt emission, the striped jet model provides a promising approach to connect various stages of gamma-ray burst (GRB) due to its robust predictions. By using constraints on magnetization and bulk Lorentz factors of the jet flow, the model is tested for GRB flow and its predictions for prompt emission are studied. It is found that the model agrees with observed prompt emission spectra in the majority of bursts, supporting a neutron star central engine over a black hole one.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. G. Suvorov, H. J. Kuan, K. D. Kokkotas
Summary: The study suggests that the precursor flare of GRB 211211A event may have resulted from the resonant shattering of one star's crust prior to coalescence, generating seismic aftershocks and low-frequency torsional modes. This interpretation is supported by the computed torsional mode properties, showing similarities between the precursor and specific torsional modes. Potential candidates for the modulations in the precursor include global or discrete Alfven modes.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
M. A. Aloy, M. Obergaulinger
Summary: The study explores the post-collapse evolution of compact, massive, low-metallicity stars, showing that small changes in the magnetic field and rotation can have significant impacts. The fate of the protoneutron star (PNS) largely depends on the strength of the poloidal magnetic field, with weak fields leading to the collapse of PNS into a black hole within seconds. Certain models demonstrate the potential for producing protomagnetars, avoiding or delaying black hole formation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Konstantinos N. Gourgouliatos, Samuel K. Lander
Summary: The evolution of magnetic fields in neutron-star crusts is driven by the Hall effect and Ohmic dissipation until the crust reaches a point of failure where standard evolution equations are no longer valid. Plastic flow in the crust affects Hall effect, sometimes even enhancing its impact. Differences in the impact of plastic flow are more pronounced in the toroidal field compared to the poloidal field.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
M. Obergaulinger, M. A. Aloy
Summary: The collapse of massive star cores can have various outcomes regarding energy release, nucleosynthesis, and remnants. The relationship between explosion and remnant types and the properties of the progenitors is still an open question. The rotation and magnetic fields in Wolf-Rayet stars may explain extreme events like superluminous supernovae and gamma-ray bursts.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Joseph Bretz, C. A. van Eysden, Bennett Link
Summary: The highly tangled magnetic field of a magnetar can support shear waves, similar to Alfvdn waves. By studying the interaction between the internal shear waves and relativistic Alfvdn shear waves in the magnetosphere, it is possible to explain the quasi-periodic oscillations observed in the giant flare of SGR 1900+14. Energy deposition in a volume spanning the stellar surface can produce detectable modulations of magnetospheric currents and explain the observed rise time of the radiative event.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Hirotaka Ito, Oliver Just, Yuki Takei, Shigehiro Nagataki
Summary: This study presents a global model of prompt emission from a short gamma-ray burst, describing the evolution of the central black hole torus system, jet propagation, transition into free expansion, and photospheric emission. The modeling shows the impact of the torus wind on the jet and emission, leading to correlations among spectral peak energy, isotropic energy, and peak luminosity. The comparison with GRB 170817A disfavors the photospheric emission scenario and supports alternative scenarios like cocoon shock breakout.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
O. Just, I Kullmann, S. Goriely, A. Bauswein, H-T Janka, C. E. Collins
Summary: This study analyzes the kilonova emission from the material ejected during the early phase of a neutron star merger using hydrodynamics simulations. The results show that the photosphere is generally ellipsoidal with small-scale structures, and the emission is stronger towards the pole than the equator. The kilonova peaks in the near-infrared frequency regime after 0.7-1.5 days with varying luminosities and photospheric temperatures. The study also highlights the importance of reliable neutrino transport modeling.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
I Kullmann, S. Goriely, O. Just, R. Ardevol-Pulpillo, A. Bauswein, H-T Janka
Summary: This study investigates the impact of neutrino interactions on r-process element nucleosynthesis and heating rate in the dynamical ejecta of neutron star-neutron star mergers. The material ejected from four merger systems is studied using hydrodynamical simulations that consider neutrino effects. The results show that neutrinos emitted by the post-merger remnant significantly affect the neutron richness of the dynamical ejecta and the nucleosynthesis of r-process elements. The composition of the ejecta and the rate of radioactive decay heating are found to be relatively independent of system parameters.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
O. Just, S. Goriely, H-Th Janka, S. Nagataki, A. Bauswein
Summary: The absorption of neutrinos affects the electron fraction (Y-e), pushing it towards 0.5 outside the torus and increasing the equilibrium value inside. Additionally, more compact tori result in lower Y-e values, with a strong r-process potentially limited to phases of high mass-infall rates.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Correction
Astronomy & Astrophysics
O. Just, I Kullmann, S. Goriely, A. Bauswein, H-t Janka, C. E. Collins
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
O. Just, M. A. Aloy, M. Obergaulinger, S. Nagataki
Summary: This study presents global models of collapsars and finds that neutron-rich, neutrino-dominated accretion flows are only established for short times or relatively low viscosities, while stable NDAFs are unable to release neutron-rich ejecta. The research suggests that collapsar models based on the alpha-viscosity are inefficient r-process sites and that magnetohydrodynamic effects may be required to generate neutron-rich outflows to improve the prospects for obtaining neutron-rich ejecta.
ASTROPHYSICAL JOURNAL LETTERS
(2022)
Article
Astronomy & Astrophysics
Chiaki Kobayashi, Ilya Mandel, Krzysztof Belczynski, Stephane Goriely, Thomas H. Janka, Oliver Just, Ashley J. Ruiter, Dany Vanbeveren, Matthias U. Kruckow, Max M. Briel, Jan J. Eldridge, Elizabeth Stanway
Summary: By comparing galactic chemical evolution models with observed elemental abundances, we find that neutron star mergers can only be a major r-process site if they have short delay times and significant ejecta masses at low metallicities, influenced by the masses of the compact objects. Specifically, black hole-neutron star mergers, depending on black hole spins, can contribute significantly to the early chemical enrichment of the Milky Way. However, none of the binary population synthesis models used in this study can currently reproduce the observed elemental abundance, pointing to potential shortcomings in binary evolution models.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
I Kullmann, S. Goriely, O. Just, A. Bauswein, H-T Janka
Summary: Theoretically predicted yields of elements created by the r-process have large uncertainties due to incomplete nuclear knowledge and approximative hydrodynamical modeling. This study examines the impact of nuclear uncertainties on r-process abundance distribution and heating rates using different nuclear input models. The results show modest effects on abundance distribution and early heating rates, but more significant effects on late-time heating rates, especially related to fission. The study also emphasizes the importance of considering multiple trajectories and the adopted conditions for accurate quantification of nuclear uncertainties. In addition, the nuclear uncertainties have an impact on the estimated age of metal-poor stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Christine E. Collins, Andreas Bauswein, Stuart A. Sim, Vimal Vijayan, Gabriel Martinez-Pinedo, Oliver Just, Luke J. Shingles, Markus Kromer
Summary: The detection of GW170817 and its electromagnetic counterpart AT2017gfo has provided valuable constraints for theoretical models of neutron star mergers and nucleosynthesis. Using a Monte Carlo radiative transfer code, the authors simulate synthetic light curves of the dynamical ejecta from a neutron star merger, taking into account neutrino interactions. They find that emission along polar lines of sight is brighter than that along equatorial lines of sight, and the bolometric light curve exhibits a monotonic decline with a shoulder when the ejecta becomes optically thin. The observed color evolution of AT2017gfo is reproduced by the simulation. The addition of a spherically symmetric secular ejecta component enhances the emission, leading to a shift in the shoulder time from 1-2 days to 6-10 days.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
O. Just, V. Vijayan, Z. Xiong, S. Goriely, T. Soultanis, A. Bauswein, J. Guilet, H. -Th. Janka, G. Martinez-Pinedo
Summary: We investigate the nucleosynthesis and kilonova properties of binary neutron star merger models that lead to intermediate remnant lifetimes until black hole formation. Our study provides a consistent end-to-end modeling of the system and its observables, using a combination of hydrodynamics, nucleosynthesis, and radiative transfer tools. Our findings show that asymmetric progenitors lead to shorter remnant lifetimes and enhanced ejecta masses, while the integrated production of lanthanides and heavier elements in such binary systems is subsolar, suggesting a subdominant contribution to r-process enrichment. The complexity of the models is taken into account in estimating kilonova light curves, which show promising agreement with observations at later times but exhibit inconsistencies at early times.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
Oliver Just, Sajad Abbar, Meng-Ru Wu, Irene Tamborra, Hans-Thomas Janka, Francesco Capozzi
Summary: This study investigates the role of fast neutrino flavor conversion in black hole accretion disks formed in neutron-star mergers or collapsing stars. The results show that fast conversions enhance the cooling rates of the disk, reduce the electron fraction, and increase the production of elements in the rapid neutron-capture process. Additionally, fast conversions prolong the duration of the kilonova event.
Proceedings Paper
Physics, Multidisciplinary
Oliver Just, Andreas Bauswein, Stephane Goriely, Hirotaka Ito, Hans-Thomas Janka, Shigehiro Nagataki
FAIR NEXT GENERATION SCIENTISTS (FAIRNESS2019)
(2020)
Article
Physics, Multidisciplinary
Andreas Bauswein, Oliver Just, Hans-Thomas Janka, Nikolaos Stergioulas
ACTA PHYSICA POLONICA B
(2020)
Article
Astronomy & Astrophysics
Robert Glas, H-Thomas Janka, Tobias Melson, Georg Stockinger, Oliver Just
ASTROPHYSICAL JOURNAL
(2019)
Article
Astronomy & Astrophysics
Robert Glas, Oliver Just, H. -Thomas Janka, Martin Obergaulinger
ASTROPHYSICAL JOURNAL
(2019)