LISA-13 International Symposium on Gravitational Waves

Prof. Rajesh Dubey, participated in LISA-13 International Symposium and presented his talk about the topic

Hubble’s Constant with GW170817 Standard Siren and GW190814 Dark Siren

He talked about how Hubble’s Constant can be calculated by Gravitational Waves events like GW170817 (Standard Siren) and GW190814 (Dark Siren) The details of the talk are as follows:

The local universe expansion rate is one of the most fundamental and important cosmological parameters. This value which is known by the name of Hubble’s Constant is scientifically measured by electromagnetic sources called the distance ladder. Surprisingly, using Gravitational Wave (GW) analysis this value can be measured making GW sources another significant method to act as standard sirens with their electromagnetic counterparts from their host galaxy. The gravitational wave event GW 170817 was the outcome of the merger of two different neutron stars. The electromagnetic event was recorded from the host galaxy NGC4993. The GW170817 has been a huge success in this direction measuring the value of universe acceleration H0 = 70.0+12.0 −8.0 kms−1 Mpc−1 The results obtained from this GW event is analyzed and compared with the other observations done with traditional methods of CMB and Cosmic Distance Ladder. Another event in this series GW190817 is Compact Binary Coalescence involving a 22.2 – 24.3 Solar Masses Blackhole and a compact object with a mass of 2.50 – 2.67 Solar Masses. The EM counterpart of this event is unknown so far and hence the event is named Dark Siren. The detection of gravitational waves from the merger event GW190814 reveals a different picture. The Hubble’s value proposed with this even is close to H0 = 75+59 −13 km s−1Mpc−1 .The source GW190814 which involves a massive black hole and the other compact object as the lightest black hole or the heaviest neutron star was localized to 18.5 deg2 at a distance of Mpc. The diversity of the two events can be used to measure the expansion rate of the universe. This can also be used to verify this rate in different directions of the universe.