Thread by @cplberry

Getting ready to watch my first #APSApril session on the latest @ego_virgo & @LIGO results! 🍿

https://twitter.com/LIGO/status/1251558578726502401

Chad Hanna is reviewing our third observing run. Look at the performance of @ego_virgo, @LIGOWA & @LIGOLA. Phenomenal sensitivity and amount of observing time: at least one detector observing for >96% of the time!

Hanna reviews our first detection of O3, a massive binary neutron star system #GW190425 arxiv.org/abs/2001.01761

And here is our new result #GW190412! This is a binary black hole with unequal masses. You can read the paper now dcc.ligo.org/LIGO-P190412/p… #APSApril

Next @mayaKfish reviews the properties of #GW190412 It has unequal masses. This enables use to make a good measurement of the spin of the larger black hole. It is *not* zero! #APSApril

Using our observations of binary black holes for O1 and O2, @mayaKfish explains that it looks like equal mass pairings are preferred. However, now #GW190412 shows that some binaries have unequal masses. It is an exceptional system 🧐 #APSApril

If we model the mass ratio (q) distribution as a power law p(q) ~ q^-beta_q, then adding in #GW190412 changes the results significantly. We learn a lot about the power-law from this one system

We did an outlier analysis for #GW190412. @mayaKfish explains that the mass ratio measurement is robust under use of a population prior. It is an unusual system, only expected amongst a set of 11 detections 0.4-12% of the time #APSApril

Moving on, @mayaKfish talks about the maximum mass for black holes. We can potentially understand pair-instability supernovae, measure cosmological parameters, and look for hierarchical mergers. Nice shout-out to @ChaseBKimball's talk on Monday! #APSApril

Next @maxisi reviews the detection of #GW190412. It is a clear detection observed by our three-detector @ego_virgo, @LIGOLA, @LIGOWA network #APSApril

Spin measurements for #GW190412! @maxisi explains measurement of non-zero spin aligned with orbital angular momentum, and some constraints on spin in the orbital plane (but no evidence for strong precession). Combining these gives bounds on the primary spin #APSApril

We model gravitational waves as an expansion in spin-weighted spherical harmonics. Normally the lowest are sufficient. @maxisi explains that due to #GW190412's mass ratio, we can clearly spot the (3,3) mode for the first time #APSApril

Using #GW190412 we've tested general relativity using a signal from an unequal mass binary. @maxisi shares new results. @AlbertEinstein is still not wrong yet! #APSApril

Ryan Fisher gives an overview of our search for gravitational waves coincident with gamma-ray bursts. We can't always be as lucky as with GW170817, so we do careful searches. Paper coming soon #APSApril

Ryan Maggee (@penn_state) discusses early warning of gravitational wave candidates. Giving early warning helps multimessenger follow-up catch emission as it happens. Early alerts have more uncertain localizations, but we can update these as we go #APSApril

On the connection between binaries and their host environments, @decohere explain how we can use the redshift distribution of sources to distinguish formation channels. Only 30 binary neutron stars host galaxies are needed to tell channels apart #APSApril

I was presenting at #APSApril this morning, so no live tweeting. Thanks @AstroKPJ for catching this

https://twitter.com/AstroKPJ/status/1251910354231320576

Excellent talk from @ynxmonica on predicting the population of binary black holes! Changing the input physics can have important consequences. Using detailed MESA simulations, we find that fewer systems go through common envelope evolution, reducing rates by ~3–4 #APSApril

Halston Lim is looking at triples! Looks like we need to include relativistic effects to model their evolution properly. Post-Newtonian expansions always make things better #APSApril

@actualdrdoctor explains how to model black holes made from smaller black holes using a cunning coagulation scheme. (Coagulation is an excellent word). #APSApril

Nathan Steinle discusses predictions for black hole spin (magnitude and orientation) through different isolated binary evolution prescriptions. He finds that you can get some misalignment of spins. Paper coming soon #APSApril

Tom Callister (@FlatironCCA) discusses how to measure the redshift distribution of compact binaries. From @LIGO/@ego_virgo observations we know the local merging rate. Using the stochastic background gives us extra information, even an upper limit is useful! #APSApril