LIGO-O2Catalog

LIGO and Virgo report on all the compact binaries found in their most recent observing run (O2). We report on a few new binary black holes (BHs) and their properties; reassess our inference about previously-reported binaries; and infer how often that different kinds of compact binary coalesce. We find no very massive BHs, suggesting an upper mass limit as would be expected from stellar evolution. We find that BH spins are unlikely to be large. Unfortunately, given small BH spins, we can’t tell much about BH spin-orbit (mis)-alignment, yet.

For experts:Why should you care? The universe provides a symphony of mergers and, by listening to it, we’re learning more about how the chorus is assembled. We don’t hear loud, deep voices (BHs) in this chorus, beyond a certain size. Because that mass cutoff resembled a boundary set by pair-instability SN, which we expected to be visible in GW observations, we might be seeing hints of a characteristic feature of stellar evolution in our data, for the first time. Unfortunately, we can’t distinguish between cluster and field formation yet using spin-orbit orientations, as I proposed a decade ago, but we should be able to soon. And more broadly we can begin to compare the detailed predictions for the mass and spin distribution produced by formation scenarios like those I’ve worked on to what we see.

A personal note: We had dreams a decade ago that results like these would be possible (see eg slides 21,22, and 27 in a talk of mine from 2009). It’s incredibly exciting and satisfying to see these dreams being realized.

For more information:

• Catalog, submitted to PRX, with a public data release available at LIGO DCC; see also the GW open science center.

• Population of binary black holes, with an embedded data release.

You can find all of the papers which LIGO and Virgo released this week at papers.ligo.org.

RIFT and the O2 catalog: Our parameter inference code RIFT was used to compare gravitational wave observations to a few expensive but state-of-the-art models for compact binaries, notably including direct comparison to numerical relativity.

PopModels and the BBH merger rate: Daniel Wysocki’s population code PopModels is one of the methods used to compare gravitational wave observations to different candidate populations of binary black holes. We used this to tell how often different kinds of BH binaries merged, extending our previous demonstration and preliminary results. (Dan is helping present these LVC results at the conference where they’re being introduced.)