English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Context: Mergers of neutron stars (NS) and black holes (BH) are among thestrongest sources of gravitational waves and are potential central engines forshort gamma-ray bursts. Aims: We aim to compare the general relativistic (GR)results by other groups with Newtonian calculations of models with equivalentparameters. We vary the mass ratios between NS and BH and the compactness ofthe NS. The mass of the NS is 1.4 M_sol. We compare the dynamics in theparameter-space regions where the NS is expected to reach the innermost stablecircular orbit (ISCO) before being tidally disrupted (mass shedding, MS) andvice versa. Methods: The hydrodynamics is evolved by a Newtonian PPM schemewith four levels of nested grids. We use a polytropic EoS (Gamma=2), as wasdone in the GR simulations. However, instead of full GR we use a Newtonianpotential supplemented by a Paczynski-Wiita-Artemova potential for the BH, bothdisregarding 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 massremains outside the BH. If the mass ratio is small (Q=2 or 3) or the NS is lesscompact (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 atidal arm. For small mass ratios the tidal arm can wrap around the BH to form athick disk. When including the effects of BH spin-up or spin-down by theaccreted matter, more mass remains in the surroundings (0.2-0.3 M_sol).Conclusions: Although details and quantitative results differ, the generaltrends of our Newtonian calculations are similar to the GR calculations. Aclear delimiting line that separates ISCO from the MS cases is not found.Inclusion of BH rotation as well as sufficient numerical resolution areextremely important.

Polytropic neutron star - black hole merger simulations with a Paczynski-Wiita potential