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Merger seismology: Distinguishing massive merger products from genuine single stars using asteroseismology

Abstract (Expand)

Products of stellar mergers are predicted to be common in stellar populations and can potentially explain stars with peculiar properties. When the merger occurs after the initially more massive star …ar has evolved into the Hertzsprung gap, the merger product may remain in the blue part of the Hertzsprung–Russell diagram for millions of years. Such objects could, therefore, explain the overabundance of observed blue stars, such as blue supergiants. However, it is currently not straightforward to distinguish merger products from genuine single stars or other stars with similar surface diagnostics. In this work, we made detailed asteroseismic comparisons between models of massive post-main-sequence merger products and genuine single stars to identify which asteroseismic diagnostics can be used to distinguish them. In doing so, we developed tools for the relatively young field of merger seismology. Genuine single stars in the Hertzsprung gap are fully radiative, while merger products have a convective He-burning core and convective H-burning shell while occupying similar locations in the Hertzsprung–Russell diagram. These major structural differences are reflected in lower asymptotic period spacing values for merger products and the appearance of deep dips in their period spacing patterns. Our genuine single-star models with masses above roughly 11.4 solar masses develop short-lived intermediate convective zones during their Hertzsprung gap evolution. This also leads to deep dips in their period spacing patterns. Because of the lack of a convective core, merger products and genuine single stars can be distinguished based on their asymptotic period spacing value in this mass range. We performed the comparisons with and without the effects of slow rotation included in the pulsation equations and conclude that the two types of stars are seismically distinguishable in both cases. The observability of the distinguishing asteroseismic features of merger products can now be assessed and exploited in practice.

Authors: J. Henneco, F. R. N. Schneider, S. Hekker, C. Aerts

Date Published: 1st Oct 2024

Publication Type: Journal

Breaking Strong Alkynyl-Phenyl Bonds: Poly(para-phenylene ethynylene)s under Mechanical Stress

Abstract

Not specified

Authors: Maximilian Elter, Matthias Brosz, Daniel Sucerquia, Andrei Kuzhelev, Denis C. Kiesewetter, Markus Kurth, Andreas Dreuw, Thomas F. Prisner, Jan Freudenberg, Uwe H. F. Bunz, Frauke Gräter

Date Published: 27th Sep 2024

Publication Type: Journal

Efficient large-scale nonstationary spatial covariance function estimation using convolutional neural networks

Abstract

Not specified

Authors: Pratik Nag, Yiping Hong, Sameh Abdulah, Ghulam A. Qadir, Marc G. Genton, Ying Sun

Date Published: 12th Sep 2024

Publication Type: Journal

Physics-based vs. data-driven 24-hour probabilistic forecasts of precipitation for northern tropical Africa

Abstract

Not specified

Authors: Eva–Maria Walz, Peter Knippertz, Andreas H. Fink, Gregor Köhler, Tilmann Gneiting

Date Published: 1st Sep 2024

Publication Type: Journal

Testing a non-local 1-equation turbulent convection model: A solar model

Abstract (Expand)

Context: Turbulent convection models treat stellar convection more physically than standard mixing-length theory by including non-local effects. We recently successfully applied the Kuhfuss version to … convective cores in main sequence stars. Its usefulness for convective envelopes remains to be tested. Aims: The solar convective envelope constitutes a viable test bed for investigating the usefulness of the 1-equation Kuhfuss turbulent convection model. Methods: We used the one-dimensional stellar evolution code GARSTEC to calculate a standard solar model with the 1-equation Kuhfuss turbulent convection model, and compared it to helioseismic measurements and a solar model using standard mixing-length theory. Additionally, we investigated the influence of the additional free parameters of the convection model on the solar structure. Results: The 1-equation Kuhfuss model reproduces the sound-speed profile and the lower boundary of the convective region less well than the mixing-length model, because the inherent non-local effects overestimate the amount of convective penetration below the Schwarzschild boundary. We trace this back to the coupling of the temperature gradient to the convective flux in the 1-equation version of the Kuhfuss theory. Conclusions: The temperature stratification of the solar convective envelope is not well modelled by the 1-equation Kuhfuss turbulent convection model, and the more complex 3-equation version is needed to improve the modelling of convection in the envelopes of 1D stellar evolution models.

Authors: T. A. M. Braun, F. Ahlborn, A. Weiss

Date Published: 1st Sep 2024

Publication Type: Journal

NFDI4Health Local Data Hubs Implementing a Tailored Metadata Schema for Health Data

Abstract (Expand)

Introduction: NFDI4Health is a consortium funded by the German Research Foundation to make structured health data findable and accessible internationally according to the FAIR principles. Its goal is …s. Its goal is bringing data users and Data Holding Organizations (DHOs) together. It mainly considers DHOs conducting epidemiological and public health studies or clinical trials. Methods: Local data hubs (LDH) are provided for such DHOs to connect decentralized local research data management within their organizations with the option of publishing shareable metadata via centralized NFDI4Health services such as the German central Health Study Hub. The LDH platform is based on FAIRDOM SEEK and provides a complete and flexible, locally controlled data and information management platform for health research data. A tailored NFDI4Health metadata schema for studies and their corresponding resources has been developed which is fully supported by the LDH software, e.g. for metadata transfer to other NFDI4Health services. Results: The SEEK platform has been technically enhanced to support extended metadata structures tailored to the needs of the user communities in addition to the existing metadata structuring of SEEK. Conclusion: With the LDH and the MDS, the NFDI4Health provides all DHOs with a standardized and free and open source research data management platform for the FAIR exchange of structured health data.

Authors: Xiaoming Hu, Haitham Abaza, Rene Hänsel, Masoud Abedi, Martin Golebiewski, Wolfgang Müller, Frank Meineke

Date Published: 30th Aug 2024

Publication Type: InProceedings

Using Health IT Standards to Facilitate Metadata Exchange Between Research Data Management Systems

Abstract (Expand)

The National Research Data Infrastructure for Personal Health Data (NFDI4Health) uses Local Data Hubs (LDHs) to manage locally research studies, documents and sensitive personal data to support controlled …ort controlled data sharing. While research data management (RDM) systems facilitate the storage and preparation of data and metadata as well as organizational access, they often lack support for interoperability standards of the application domain. To support the exchange with external registries of research studies, we chose 17 attributes to characterize the most relevant aspects of clinical trials (in the following named “metadata profile”). We implemented the metadata profile in the RDM system FAIRDOM SEEK using core attributes and SEEK’s extended metadata feature and created a mapping conforming to the Health Level 7 Fast Healthcare Interoperability Resources (FHIR) standard version R4. Finally, we implemented a prototype application interface for exports in FHIR-JSON format. We plan to extend the interface to serve central registries and support specific FHIR Implementation Guides from various use cases.

Authors: Matthias Löbe, Xiaoming Hu, Sophie A.I. Klopfenstein

Date Published: 22nd Aug 2024

Publication Type: Journal

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