To leading order, the gravitational-wave (GW) signal from binary neutron stars depends on the individual spins, χ_1 and χ_2, only through the effective spin parameter χ_ eff. We present the first systematic investigation of individual-spin effects on ejecta, r-process nucleosynthesis, and kilonova emission, including comparisons at fixed total mass, mass ratio and χ_ eff. We use numerical relativity ejecta from three total mass regimes with the finite-temperature, composition-dependent SFHo equation of state and neutrino emission and absorption. For M_ tot=2.55 M_⊙ at fixed χ_ eff=0, individual spins change the dynamical ejecta mass by a factor of ∼45, while the absolute A≥140 yield spans more than two orders of magnitude and the lanthanide to light r-process mass ratio increases from ∼2 to ∼70. Prompt-collapse 4.10 M_⊙ models show heavy-element yield differences exceeding four orders of magnitude at χ_ eff=0. The kilonova retains the individual-spin imprint, with peak brightness differences reaching ∼0.9 mag. At 40 Mpc, all three fixed χ_ eff=0 pairs remain above adopted depths at common epochs for all viewing angles, with same-epoch colour differences reaching ∼1.5 mag. The colour imprint persists when the simulation-derived secular ejecta are replaced by the same parametric disc outflow, indicating that disc mass differences are not the primary driver and that dynamical ejecta make an important contribution. Neutrino absorption systematically brightens the kilonova and shifts peak-associated colours blueward. These EM signatures can break the degeneracy between individual spins in the GW signal.

We investigate the effect of spin on equal- and unequal-mass binary neutron star mergers using finite-temperature, composition-dependent Steiner-Fischer-Hempel equation of state with parameter set 'o', via 3 + 1 general relativistic hydrodynamics simulations, which take into account neutrino emission and absorption. Equal-mass, irrotational cases that have a mass of M-1 ,M- 2 = 1 . 27 M-circle dot result in a long-lived neutron star, while 1.52 and 2 . 05 M-circle dot cases lead to a prompt collapse to a black hole. For all cases, we analyse the effect of initial spin on dynamics, on the structure of the final remnant, its spin evolution, the amount and composition of the ejected matter, gravitational waves, neutrino energies and luminosities, and disc masses. We show that in equal-mass binary neutron star mergers, the ejected mass could reach '0 . 06 M-circle dot for highly aligned spins (chi = 0 . 67). The black hole that results from such a highly spinning, high-mass binary neutron star merger reaches a dimensionless spin of 0.92; this is the highest spin reached in binary neutron star mergers, to date.

Acoustic Deterrent Devices (ADDs) are used worldwide to deter pinnipeds from predating fish-aquaculture facilities. Desk-based noise-propagation modelling of six commercial ADD models, and a 'fictional' ADD was performed, the latter involving alternating source level, frequency, duty cycle, noise-exposure duration, and number of ADDs active simultaneously. Potential auditory impacts on marine mammals were explored using the Southall et al. (2019) criteria. Depending on operational characteristics, real ADDs were predicted to cause Temporary Threshold Shift (TTS) to Very High Frequency (VHF) cetaceans at ranges of 4-31 km, and a single fictional device operating at the highest outputs tested was predicted to cause TTS to VHF cetaceans at up to 32 km. Cumulative effects of 23 real fish-farm ADDs produced noise across large swathes of the Inner-Hebrides. The single variable causing greatest reduction in potential impact to marine mammals from fictional ADDs was SL.

C-PODs are used for Passive Acoustic Monitoring (PAM) of harbour porpoises (Phocoena phocoena) at an offshore open sea location in the German North Sea. Diel patterns of echolocation click trains are extracted from minimum inter-click interval (minICI) data by binning. The aim of this study is to reassess and refine minICI ranges of click train data with particular consideration to the binning widths. Emphasis is also placed on choosing an appropriate visualisation of these binned data. Key ecological results include presence of higher train rates during the day with intermediate minICI values defined by the range 6-28 ms and a higher train rate with short minICI values 1.25-2.00 ms at night. This indicates an increase in porpoise feeding behaviour, or change of style, at night. Click trains with long minICI values > 35 ms occur at an equal rate throughout both diel phases, suggesting a more routine behaviour, such as navigation. Results could be revealed only by judicious choice of binning widths, e.g. previously overlooked patterns within historical echolocation data. The classification methodology can be used to analyse echolocation trains from a variety of species and can be applied to any PAM data with the relevant click parameters.

The modelled acoustic characteristics of three Acoustic Harassment Devices (AHDs) deployed from a fully operational salmonid fish farm, located in the Sound of Mull, Scotland (UK) are presented, using empirical seabed and water column measurements at the same location. In the Beaufort Sea state 0, the depth range of 10-50 m is the maximum range at which AHDs are potentially audible to five marine mammal species. The species present within this survey region are: the harbour porpoise, Phocoena phocoena (99.1 km), the killer whale, Orcinus orca (110 km), the bottlenose dolphin, Tursiops truncatus (89.6 km), the common seal, Phoca vitulina (88 km), and the grey seal, Halichoerus grypus (69 km). Consequently, within the Sound of Mull, all three AHDs could be heard throughout the water column by all species. For two models of AHDs, a behavioural disturbance level of between 140 dB-180 dB is observed at 1.3 km. Habitat displacement is a cause for concern, particularly if several fish farms within a small area all deploy AHDs simultaneously. This can create a confusing sound field of varying intensity, which has potential to deter harbour porpoises from sections of their habitat. If positioned effectively, AHDs have the potential to deter all five marine mammal species from industrial operations such as aquaculture facilities. Source levels, propagation and transmission loss measurements were highly variable and should be considered as site specific, meaning new estimates should be made for each situation.

We have developed a new boundary condition for finite volume simulations of oscillating bubbles. Our method uses an approximation to the motion outside the domain, based on the solution at the domain boundary. We then use this approximation to apply boundary conditions by defining incoming characteristic waves at the domain boundary. Our boundary condition is applicable in regions where the motion is close to spherically symmetric. We have tested our method on a range of one- and two-dimensional test cases. Results show good agreement with previous studies. The method allows simulations of oscillating bubbles for long run times ( 5 × 10 5 time steps with a CFL number of 0.8) on highly truncated domains, in which the boundary condition may be applied within 0.1 % of the maximum bubble radius. Conservation errors due to the boundary conditions are found to be of the order of 0.1 % after 105 time steps. The method significantly reduces the computational cost of fixed grid finite volume simulations of oscillating bubbles. Two-dimensional results demonstrate that highly asymmetric bubble features, such as surface instabilities and the formation of jets, may be captured on a small domain using this boundary condition.

We modify an existing magnetohydrodynamics algorithm originally developed by Balsara and Spicer and later Toth to make it more compatible with a dimensionally split (DS) framework. It is based on the standard reconstruct-solve average strategy (using a Riemann solver), and relies on constrained transport to ensure that the magnetic field remains divergence free (del .B=0). The DS approach, combined with the use of a single, cell-centred grid (for both the fluid quantities and the magnetic field), means that the algorithm can be easily added to existing DS hydrodynamics codes. This makes it particularly useful for mature astrophysical codes, which often model more complicated physical effects on top of an underlying DS hydrodynamics engine, and therefore cannot be restructured easily. Several test problems have been included to demonstrate the accuracy of the algorithm, and illustrative source code has been made freely available online.

It has been known since the 1950's that the observed gas content of Galactic globular clusters (GCs) is 2-3 orders of magnitude less than the mass lost by stars between Galactic disk crossings. In this work we address the question: What happens to this stellar gas? Using an Eulerian nested grid code, we present 3D simulations to determine how stellar wind material evolves within the GC environment. We expand upon work done in the 70's and move a single-mass King-model GC through the Galactic halo medium, stripping a 10^5 Msun GC of its intra-cluster medium but predicting a detectable medium for a 10^6 Msun cluster. We find from new multi-mass King model simulations, the first to incorporate empirical mass-loss formulae, that the single-mass King model underestimates the retention of intra-cluster gas in the cluster. Lastly, we present a simple discretised multi-mass GC model, which yields lower levels of intra-cluster medium compared to the continuous single- and multi-mass King models. Our results show that there is still an issue with the predicted intra-cluster gas content of massive GCs. We conclude that by modelling GC systems more accurately, in particular the stellar structure and description of mass loss, we will be able to work towards resolving this issue and begin to fill in some of the gaps in our understanding of the evolution of globular clusters.

Context: Mergers of neutron stars (NS) and black holes (BH) are among the strongest sources of gravitational waves and are potential central engines for short gamma-ray bursts. Aims: We aim to compare the general relativistic (GR) results by other groups with Newtonian calculations of models with equivalent parameters. We vary the mass ratios between NS and BH and the compactness of the NS. The mass of the NS is 1.4 M_sol. We compare the dynamics in the parameter-space regions where the NS is expected to reach the innermost stable circular orbit (ISCO) before being tidally disrupted (mass shedding, MS) and vice versa. Methods: The hydrodynamics is evolved by a Newtonian PPM scheme with four levels of nested grids. We use a polytropic EoS (Gamma=2), as was done in the GR simulations. However, instead of full GR we use a Newtonian potential supplemented by a Paczynski-Wiita-Artemova potential for the BH, both disregarding and including rotation of the BH. Results: If the NS is compact (C=0.18) it is accreted by the BH more quickly, and only a small amount of mass remains outside the BH. If the mass ratio is small (Q=2 or 3) or the NS is less compact (C=0.16 or less) the NS is tidally torn apart before being accreted. Although most of the mass is absorbed by the BH, some 0.1 M_sol remain in a tidal arm. For small mass ratios the tidal arm can wrap around the BH to form a thick disk. When including the effects of BH spin-up or spin-down by the accreted matter, more mass remains in the surroundings (0.2-0.3 M_sol). Conclusions: Although details and quantitative results differ, the general trends of our Newtonian calculations are similar to the GR calculations. A clear delimiting line that separates ISCO from the MS cases is not found. Inclusion of BH rotation as well as sufficient numerical resolution are extremely important.

Aims. We investigate the efficiency and time-dependence of thermally and cosmic ray driven galactic winds for the metal enrichment of the intra-cluster medium (ICM) using a new analytical approximation for the mass outflow. The spatial distribution of the metals are studied using radial metallicity profiles and 2D metallicity maps of the model clusters as they would be observed by X-ray telescopes like XMM-Newton.Methods. Analytical approximations for the mass loss by galactic winds driven by thermal and cosmic ray pressure are derived from the Bernoulli equation and implemented in combined N-body/hydrodynamic cosmological simulations with a semi-analytical galaxy formation model. Observable quantities like the mean metallicity, metallicity profiles, and 2D metal maps of the model clusters are derived from the simulations.Results. We find that galactic winds alone cannot account for the observed metallicity of the ICM. At redshift z = 0 the model clusters have metallicities originating from galactic winds which are almost a factor of 10 lower than the observed values. For massive, relaxed clusters we find, as in previous studies, a central drop in the metallicity due to a suppression of the galactic winds by the pressure of the ambient ICM. Combining ram-pressure stripping and galactic winds we find radial metallicity profiles of the model clusters which agree qualitatively with observed profiles. Only in the inner parts of massive clusters the observed profiles are steeper than in the simulations. Also the combination of galactic winds and ram-pressure stripping yields too low values for the ICM metallicities. The slope of the redshift evolution of the mean metallicity in the simulations agrees reasonably well with recent observations.

We have investigated a transport mechanism for the enrichment of the intra-cluster medium (ICM) due to Active Galactic Nuclei (AGN) outflows, induced by galaxy interactions. We assumed flybys and mergers of late-type galaxies as a triggering mechanism for the AGN activity. The simulation setup of our investigations consists of a combined N-Body/hydrodynamic technique for dark matter and the ICM and a semi-analytical galaxy formation model. In total, we have performed eight different galaxy cluster simulations, spanning a broad mass range. The obtained metalicity maps and profiles of the ICM were compared to the maps and profiles obtained from the X-ray observatories of different galaxy clusters. The main result is: AGN-triggered outflows of the inter-stellar medium (ISM) in the central parts of late-type galaxies do not contribute significantly to the observed metalicities found in the ICM of galaxy clusters.

Compact object mergers have long been speculated to be a possible site of r-process nucleosynthesis.While most attention has been focused on the cold decompression of neutron star matter ejected from the merger, other sites within the merger likely contribute to its nucleosynthetic output.Here we consider hot outflows from the accretion disk that forms around the black hole following a black hole -neutron star merger.We begin with the results of a three-dimensional numerical merger model and carefully calculate the neutrino and antineutrino fluxes emitted from the accretion disk.We find that neutrino interactions on free nucleons in the outflowing material result in neutron excesses such that at least a weak r-process is produced and in some cases a main r-process as well.Additionally, we find that the weak r-process pattern calculated for certain trajectories compares favorably to the pattern observed in a weak r-process-enhanced halo star.

We investigate the long-term evolution and observability of remnants originating from the merger of compact binary systems and discuss the differences to supernova remnants. Compact binary mergers expel much smaller amounts of mass at much higher velocities, as compared to supernovae, which will affect the dynamical evolution of their remnants. The ejecta of mergers consist of very neutron rich nuclei. Some of these neutron rich nuclei will produce observational signatures in form of gamma ray lines during their decay. The composition of the ejecta might even give interesting constraints about the internal structure of the neutron star. We further discuss the possibility that merger remnants appear as recently discovered ‘dark accelerators’ which are extended TeV sources which lack emission in other bands.

We have used a 3D hydrodynamics code to trace the evolution of gas as it leaves evolved giant stars and enters the intracluster medium (ICM) of Galactic globular clusters (GC). Mechanisms for removing this ICM gas from the GC potential are investigated.

We consider hot accretion disk outflows from black hole-neutron star mergers in the context of the nucleosynthesis they produce. We begin with a three-dimensional numerical model of a black hole-neutron star merger and calculate the neutrino and antineutrino fluxes emitted from the resulting accretion disk. We then follow the element synthesis in material outflowing the disk along parameterized trajectories. We find that at least a weak r-process is produced, and in some cases a main r-process as well. The neutron-rich conditions required for this production of r-process nuclei stem directly from the interactions of the neutrinos emitted by the disk with the free neutrons and protons in the outflow.

The fate of gas in cluster galaxies through the dynamical processes of ram-pressure stripping and winds is modelled using a combined N-body, phenomenological and hydrodynamical approach. This allows us to model the interaction between cluster galaxies and the intra-cluster medium, and study the consequences of this interaction on the metallicity of the hot cluster gas as well as the properties of the cluster galaxies. We summarize our results for the ICM metallicity, and discuss a first attempt to improve the predictions for the properties of cluster galaxies.