Gravitational-wave astronomy — Stochastic nanohertz gravitational-wave background in pulsar timing

LIGO-Virgo O2 data could detect, or at least meaningfully constrain, primordial black hole dark matter through mergers pairing a subsolar component with a primary above about 2 solar masses.

Four candidates passed a signal-to-noise threshold of 8 and a false alarm rate of 2 per year, but none was statistically significant; assuming a null, the 90% upper limits on the primordial black hole dark-matter fraction stayed above 1 for every mass function and both early and late binary formation prescriptions, so no part of the parameter space was excluded.

Why it matched: same research area

The observed correlation between effective spin and mass ratio is a property of the binary black hole population itself.

Fitting the two recently identified subpopulations separately, the correlation weakened significantly or disappeared altogether for the low-mass subpopulation once a second effective-spin distribution was allowed for the high-mass one, and Bayesian evidence strongly favoured two separate spin distributions over one mass-ratio-dependent distribution (ln B > 4.2).

Why it matched: same research area