• Major upgrade of SPHINCS_BSSN:
- We have developed a much more accurate mapping of particle properties (simulating matter) to our adaptive mesh (simulating space-time). Our new methodology (“Local Regression Estimate”, LRE) calculates mapping kernels by minimizing in a sophisticated way error functionals. Our LRE approach has substantially increased the accuracy of our code, which we will from throughout the project.
- We have further improved our particle-mesh initial data. Both of these topic are described in Rosswog et al., Frontiers in Applied Mathematics and Statistics, Vol. 9 (2023).
• Improving the accuracy of particle hydrodynamics. Standard Smoothed Particle Hydrodynamics (SPH) does not enforce some consistency relations that are desirable for high-accuracy approximations. I have developed a new particle hydrodynamics method in which these relations are fulfilled by construction. A corresponding method paper has just been submitted (Rosswog,2024). Soon to be adapted for our code SPHINCS_BSSN.
• Together with my former Postdoc Oleg Korobkin, I have summarized the current understanding of “Heavy elements and electromagnetic transients from neutron star mergers” in a recent review article.
• Together with INSPIRATION-funded Postdoc Jan-Erik Christian I have explored which first order phase transitions to quark matter are possible in neutron stars, see Christian et al. (2024).
• We have realized that a non-negligible fraction of neutron stars contain a single rapidly spinning neutron star together with a non-spinning companion. We have predicted different multi-messenger signatures of such mergers, see Rosswog et al. 2024a.
• Together with Nikhil Sarin, Stockholm University, I have explored the impact of the nuclear heating rate on the appearance of kilonovae and the inference of their parameters from a neutron star merger observation, see Sarin & Rosswog 2024.
• Via general relativistic magnetohydrodynamic simulations we have investigated magnetic field evolution in a neutron star merger and find that starting from realistic initial B-fields leads to a substantial delay in the jet formation, see Aguilera-Miret et al. (2024). A further paper on the magnetic field evolution in neutron star mergers is about to be submitted.
• A number of previous simulations had seen a small, but observationally very important fast ejecta component (v>0.5c) whose origin was unclear. Using SPHINCS_BSSN, we have identified two ejection mechanisms for this matter and we predicted its observational signatures, see Rosswog et al. 2024b.
