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

In their most recent observing run, the LIGO-Virgo-KAGRA (LVK) Collaborationobserved gravitational waves (GWs) from compact binary mergers with highlyasymmetric mass ratios, including both binary black holes (BBHs) and neutronstar--black holes (NSBHs). It appears that NSBHs with mass ratios $q\simeq0.2$are more common than equally asymmetric BBHs, but the reason for this remainsunclear. We use the binary population synthesis code COSMIC to investigate theevolutionary pathways leading to the formation and merger of asymmetric compactbinaries. We find that within the context of isolated binary stellar evolution,most asymmetric mergers start off as asymmetric stellar binaries. Because ofthe initial asymmetry, these systems tend to first undergo a dynamicallyunstable mass transfer phase. However, after the first star collapses to acompact object, the mass ratio is close to unity and the second phase of masstransfer is usually stable. According to our simulations, this stable masstransfer fails to shrink the orbit enough on its own for the system to merge.Instead, the natal kick received by the second-born compact object during itscollapse is key in determining how many of these systems can merge. For themost asymmetric systems with mass ratios $q\leq0.1$, the merging systems in ourmodels receive an average kick magnitude of 255 km s$^{-1}$ during the secondcollapse, while the average kick for non-merging systems is 59 km s$^{-1}$.Because lower mass compact objects, like NSs, are expected to receive largernatal kicks than higher mass BHs, this may explain why asymmetric NSBH systemsmerge more frequently than asymmetric BBH systems.

The role of natal kicks in forming asymmetric compact binary mergers