Gravitational wave sources Tomek Bulik University of Warsaw

Gravitational waves have been detected! The source – and its properties Astrophysical significance Outlook for the future Possible mechanisms of gamma ray production

The detection on Sep 14th, 2015

How does the merger look?

What is it? A binary black hole! How do we know it?

Where does it come from? Binary evolution Cluster origin

Evolutionary scenario Credit: Wojtek Gładysz

Globular clusters Paths to BHS Escaping binaries (dominating) Induced mergers inside GC Mass distribution BH production efficiency

BH production efficiency Number of merging BBH binaries per 10^6 solar masses of stars.

Dependence on the cluster mass Z=0.001 (5% Zsun)

The dominant contribution – escaping BHBH

A list of breakthroughs Detection of gravitational waves Detection of a black hole Detection of black hole binary Evidence for BHs with masses of 30 and and up to 60 solar masses Possibility to test General Relativity Possibility to test Quantum Gravity(?) The brightest source ever seen in the sky:

What next The detectors are being improved, and new detectors will be added to the network

Observing plans

Upcoming sensitivity

Expected event rates Rate estimate: In the final configuration: Range increased 3x Observations all year Efficiency will increase with KAGRA, and LIGO- India Rates can be as high as one per day

Can we have gamma rays from BHBH merger? Fermi: a weak gamma ray burst 0.4 seconds after the GW detection INTEGRAL – an upper limit, lower than the Fermi detection flux A hint, but not significant enough to claim detection Nevertheless it sparked a lot of ideas

Two BHs merging inside a star Rapidly rotating star, core fragments, makes two BHs. Subsequent merger inside a star followed by a standard GRB. (Loeb, 2016)

A remnant disk.. The first BH carries a dormant disk Before the merger the disk wakes up by tidal forces A disk is ready to accrete onto a newly formed BH after merger

BH formation triggered by the 2nd BH At the onset of a common envelope phase the tidal squeezing triggers formation of a BH inside a star. BHs inspiral inside the star, and cause a GRB after merger

Two charged BHs Charged BH moving at relativistic speeds Currents → magnetic fields → magnetopshere → particle acceleration → high energy radiation Magnetic fields → reconnection → gama - rays

Exotica Charged BHs Megers of BHs with firewalls Mergers of gravastars, boson stars, Q-stars... Release of a large amount of energy, close to the GW luminosity

Do not forget about neutron stars A fraction of the sources will contain neutron stars: NSNS and BHNS These phenomena will be rare, but will certainly be sources of gamma rays Triggers should be distributed very fast, less tan minute

Conclusions In the coming years GW sources will be plentiful Locations of the most promising sources will be manageable – down to a few square degrees. Search for EM counterparts of GW sources is a high risk - high reward activity. Quantum gravity Exotic models Speed of gravity Origin of GRBs and many more I suppose