Physics Seminar presents
Gravitational Wave Observations and the Physics of Neutron Stars

Guest Speaker: Simone Dall’Osso of SUNY Stony Brook

The first direct detection of gravitational waves (GW) from a binary black hole made by Advanced LIGO has opened the era of GW astronomy. Sources for the current detectors are catastrophic events involving neutron stars (NS) and black holes (BH), isolated or in binaries, in which huge amounts of energy are released in very small regions and short timescales. Besides GWs, bright electromagnetic (EM) transients, as well as copious emission of neutrinos and ultrarelativistic cosmic rays are expected in association to such events, making them ideal targets for multi-messenger observations. Because GW interact so weakly with the environment, they are unique probes of the physical processes occurring in the extremely dense and turbulent regions where NS/BHs form and/or collide. Because photons are easily emitted (and detected) from the surrounding regions, on the other hand, EM transients are the counterparts to GW sources that we can more effectively reveal and study. I will focus in particular on a class of highly magnetized, millisecond spinning NS, that could form both in the core-collapse of massive stars and in binary NS mergers. Such NS have been proposed as possible sources of the brightest EM transients (gamma-ray bursts, super-luminous supernovae), and as progenitors of a galactic population of peculiar X-ray pulsars (magnetars). I will present a mechanism, the so-called “spinfip” instability, by which newly born, highly magnetized, millisecond spinning NS can also produce powerful and distinctive GW signals carrying pristine information about the physics of their interiors and the equation of state (EOS) of matter at supra-nuclear density. The EM emission expected in association with these GW signals is particularly bright and carries its own signatures of the millisecond spinning NS: this makes these sources ideally suited for multimessenger studies.