Center for Theoretical Physics of the Universe (CTPU-PTC)

Exploring the Universe via Gravitational waves in the era of multi-messenger astronomy

by Dr Chunglee Kim (KASI)

CTPU Seminar Room (KAIST Munji Campus)

CTPU Seminar Room

KAIST Munji Campus

Since 2015, advanced LIGO (Laser Interferometer Gravitational-wave Observatory) in USA and advanced Virgo in Europe have been successfully discovering black holes and neutron stars via gravitational waves (GWs) in cosmological distances. After the original discovery of a black hole binary (BBH, GW150914) by LIGO, a few more BBHs are confirmed so far. BBH discoveries proved the following: (1) GW waveforms from black hole binary coalescence (inspiral-merger-ringdown phases) are well described by Einstein's general relativity and approximated waveform modelings, (2) All BHs discovered by GWs are heavier than those known in our Galaxy detected by X-rays. GW170817 is the first extragalactic neutron star - neutron star binary (NS-NS). This was discovered by GW observation (signal duration of ~1min) that was followed by an international campaign of astronomical observation via electromagnetic wave as well as neutrinos. GW170817 discovery and follow-up observations proved that a global multi-messenger network works efficiently. With the discoveries of BBHs and NS-NS by LIGO and Virgo, GW astronomy has truly begun. The next decades will be a golden era for stellar astrophysics and many surprises are expected. Furthermore, cosmology with GWs seems also promising. Distance measure by GWs for GW170817 (at 40 Mpc) is already powerful enough to put constraints on the Hubble constant. In future, there will be a global network of GW observatories on Earth and in space and broader frequency ranges will be accessible in GWs. Then, it will be possible to discriminate cosmological models and to test the Einstein's general relativity in the strong field limit. In this talk, I will discuss GW astronomy and astrophysics based on LIGO-Virgo achievements.