Friedrich Röpke

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About Friedrich Röpke:

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SEEK ID: https://publications.h-its.org/people/135

Location: Germany

ORCID: https://orcid.org/0000-0002-4460-0097

Joined: 14th Feb 2020

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Physics of Stellar Objects

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Heidelberg Institute for Theoretical Studies

Country: Germany

City: Heidelberg

Web page: https://www.h-its.org

Showing 5 out of a possible 134 Publications Advanced Publications list for this Person with search and filtering

Type Ia supernova progenitors: a contemporary view of a long-standing puzzle

Physics of Stellar Objects

Abstract

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Authors: Ashley Jade Ruiter, Ivo Rolf Seitenzahl

Date Published: 1st Dec 2025

Publication Type: Journal

DOI: 10.1007/s00159-024-00158-9

Citation: Astron Astrophys Rev 33(1),1

Created: 9th Apr 2025 at 12:49

The asymmetry of white dwarf double detonations and the observed scatter around the Phillips relation

Physics of Stellar Objects

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Context. Recent Type Ia supernova (SN Ia) simulations featuring a double detonation scenario have managed to reproduce the overall trend of the Phillips relation reasonably well. However, most, if not …ation reasonably well. However, most, if not all, multidimensional simulations struggle to reproduce the scatter of observed SNe around this relation, exceeding it substantially. Aims. In this study, we investigate whether the excessive scatter around the Phillips relation can be caused by an off-center ignition of the carbon-oxygen (CO) core in the double detonation scenario and if this can help constrain possible SN Ia explosion channels. Methods. We simulated the detonation of three different initial CO white dwarfs of 0.9, 1.0, and 1.1 M ⊙ , artificially ignited at systematically offset locations using the A REPO code. After nucleosynthetic postprocessing, we generated synthetic observables using the A RTIS code and compared these results against observational data and models of other works. Results. We find that our simulations produce synthetic observables well within the range of the observed data in terms of viewing angle scatter. The majority of the viewing angle variability seems to be caused by line blanketing in the blue wavelengths of intermediate-mass elements and lighter iron-group elements, which are asymmetrically distributed in the outer layers of the ashes. Conclusions. Our results suggest that although the off-center ignition of the CO introduces substantial line of sight effects, it is not responsible for the excessive viewing angle scatter observed in other models. Instead, this effect seems to be caused by the detonation ashes from the rather massive helium (He) shells in current state-of-the-art models. Further reducing the He-shell masses of double detonation progenitors may be able to alleviate this issue and yield observables that reproduce the Phillips relation.

Authors: Alexander Holas, Friedrich K. Röpke, Rüdiger Pakmor, Fionntan P. Callan, Josh Pollin, Stuart A. Sim, Christine E. Collins, Luke J. Shingles, Javier Moran-Fraile

Date Published: 1st Jun 2025

Publication Type: Journal

DOI: 10.1051/0004-6361/202554640

Citation: A&A 698:A269

Created: 26th Jun 2025 at 08:37, Last updated: 26th Jun 2025 at 08:38

Gravitational-wave model for neutron star merger remnants with supervised learning

Physics of Stellar Objects

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We present a time-domain model for the gravitational waves emitted by equal-mass binary neutron star merger remnants for a fixed equation of state. We construct a large set of numerical relativity … simulations for a single equation of state consistent with current constraints, totaling 157 equal-mass binary neutron star merger configurations. The gravitational-wave model is constructed using the supervised learning method of K-nearest neighbor regression. As a first step toward developing a general model with supervised learning methods that accounts for the dependencies on equation of state and the binary masses of the system, we explore the impact of the size of the dataset on the model. We assess the accuracy of the model for a varied dataset size and number density in total binary mass. Specifically, we consider five training sets of simulations uniformly distributed in total binary mass. We evaluate the resulting models in terms of faithfulness using a test set of 30 additional simulations that are not used during training and which are equidistantly spaced in total binary mass. The models achieve faithfulness with maximum values in the range of 0.980 to 0.995. We assess our models simulating signals observed by the three-detector network of Advanced LIGO-Virgo. We find that all models with training sets of size equal to or larger than 40 achieve an unbiased measurement of the main gravitational-wave frequency. We confirm that our results do not depend qualitatively on the choice of the (fixed) equation of state. We conclude that training sets, with a minimum size of 40 simulations, or a number density of approximately 11 simulations per 0.1⁢𝑀⊙ of total binary mass, suffice for the construction of faithful templates for the postmerger signal for a single equation of state and equal-mass binaries, and lead to mean faithfulness values of ℱ ≃0.95. Our model being based on only one fixed equation of state represents only a first step toward a method that is fully applicable for gravitational-wave parameter estimation. However, our findings are encouraging since we show that our supervised learning model built on a set of simulations for a fixed equation of state successfully recovers the main gravitational-wave features of a simulated signal obtained using another equation of state. This may indicate that the extension of this model to an arbitrary equation of state may actually be achieved with a manageable set of simulations.

Authors: Theodoros Soultanis, Kiril Maltsev, Andreas Bauswein, Katerina Chatziioannou, Friedrich K. Röpke, Nikolaos Stergioulas

Date Published: 2025

Publication Type: Journal

DOI: 10.1103/PhysRevD.111.023002

Citation: Phys. Rev. D 111(2),023002

Created: 24th Feb 2025 at 08:25, Last updated: 24th Feb 2025 at 08:27

From spherical stars to disk-like structures: 3D common-envelope evolution of massive binaries beyond inspiral

Physics of Stellar Objects

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Abstract

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Authors: Marco Vetter, Friedrich K. Röpke, Fabian R. N. Schneider, Rüdiger Pakmor, Sebastian T. Ohlmann, Mike Y. M. Lau, Robert Andrassy

Date Published: 1st Nov 2024

Publication Type: Journal

DOI: 10.1051/0004-6361/202451579

Citation: A&A 691:A244

Created: 18th Feb 2025 at 14:16, Last updated: 18th Feb 2025 at 14:17

Large-scale ordered magnetic fields generated in mergers of helium white dwarfs

Physics of Stellar Objects

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Authors: Rüdiger Pakmor, Ingrid Pelisoli, Stephen Justham, Abinaya S. Rajamuthukumar, Friedrich K. Röpke, Fabian R. N. Schneider, Selma E. de Mink, Sebastian T. Ohlmann, Philipp Podsiadlowski, Javier Morán-Fraile, Marco Vetter, Robert Andrassy

Date Published: 1st Nov 2024

Publication Type: Journal

DOI: 10.1051/0004-6361/202451352

Citation: A&A 691:A179

Created: 18th Feb 2025 at 14:16, Last updated: 18th Feb 2025 at 14:18

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