• Journal of The Korean Astronomical Society
• /
• v.29 no.spc1
• /
• pp.273-276
• /
• 1996

The world wide efforts for detecting gravitational waves, the detectors in vogue and the expected astrophysical sources of gravitational waves will be discussed. Ground based detectors especially, the resonant bar detectors and laser interferometers will be described with a brief mention of the space based detector (the LISA project). Astrophysical sources of gravitational waves such as coalescing binaries, supernovae, pulsars/ rotating neutron stars, stochastic background will be discussed in the context of detection.

• Publications of The Korean Astronomical Society
• /
• v.26 no.2
• /
• pp.71-87
• /
• 2011

Gravitational waves are predicted by the Einstein's theory of General Relativity. The direct detection of gravitational waves is one of the most challenging tasks in modern science and engineering due to the 'weak' nature of gravity. Recent development of the laser interferometer technology, however, makes it possible to build a detector on Earth that is sensitive up to 100-1000 Mpc for strong sources. It implies an expected detection rate of neutron star mergers, which are one of the most important targets for ground-based detectors, ranges between a few to a few hundred per year. Therefore, we expect that the gravitational-wave observation will be routine within several years. Strongest gravitational-wave sources include tight binaries composed of compact objects, supernova explosions, gamma-ray bursts, mergers of supermassive black holes, etc. Together with the electromagnetic waves, the gravitational wave observation will allow us to explore the most exotic nature of astrophysical objects as well as the very early evolution of the universe. This review provides a comprehensive overview of the theory of gravitational waves, principles of detections, gravitational-wave detectors, astrophysical sources of gravitational waves, and future prospects.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.1
• /
• pp.56.2-56.2
• /
• 2013

Compact binaries are important sources of gravitational waves. They are also prime targets for long baseline laser interferometers. In this talk, we present latest progresses made in the Galactic merger rate calculations for compact binaries in the Galactic disk, with an emphasis on NS-NS binaries. For the first time, the non-recycled pulsar found in the Double Pulsar system (PSR J0737-3039B) is included in the rate calculation. We then discuss the prospects of detecting gravitational waves for Earth-based detectors such as advanced LIGO (Laser Interferometer Gravitational-wave Observatory) in US and advanced Virgo in Europe, extrapolating the Galactic rate estimates up to the detection volume of the advanced LIGO-Virgo network, Our results support the expectation that gravitational waves emitted from compact binary mergers will be detected within a decade. However, the detection rate of gravitational waves associated with NS-NS mergers is most likely to be several per year that is much smaller than what has been previously known.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.1
• /
• pp.79.1-79.1
• /
• 2014

GRBs are the most energetic and very frequent electromagnetic events among known astronomical phenomena in the universe. The progenitor of GRBs is believed as one of most promising sources of gravitational waves. Thus, detection of gravitational wave signals associated with GRBs will be a fascinating issue. In this presentation, we describe how we search gravitational waves related to GRBs by using LIGO and Virgo data.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.1
• /
• pp.77.1-77.1
• /
• 2014

Gravitational waves predicted by the general relativity almost 100 years ago have been implicated indirectly only by astrophysical observations such as the orbital evolution of binary pulsars. The advanced detectors of gravitational waves will become operational in a few years and they are expected to make direct detection of gravitational wave signal coming from merging of binaries composed of neutron stars or stellar mass black holes from external galaxies. Korean Gravitational Wave Group (KGWG) is contributing to the possible detection through the data analysis of LIGO and Virgo. We summarize the perspectives of the gravitational wave research and the impacts of the detection in the near future in astronomy and astrophysics.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.55.4-55.4
• /
• 2019

We present the second order solutions of the cosmological gravitational waves induced by linear cosmological perturbations.

• Journal of The Korean Astronomical Society
• /
• v.28 no.1
• /
• pp.67-70
• /
• 1995

In contrast to conventional belief that extended inflation ends when the Universe percolates, we find inflation may continue at least many Hubble times even after the Universe percolates. What is observed is that inflation will not stop unless the global equation of state changes from inflationary one into radiation one. Thus the energy density of shorter wavelength gravitational waves induced by bubble collision at near the end of inflation should be at least Order $(10^2)\~O(10^3)$ times greater than previous estimation of Turner and Wilcek(TW).

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.47.2-47.2
• /
• 2011

Gravitational waves from the pulsar glitch can be detected by next generation gravitational wave observatories. We investigate characteristics of the modes that can emit the gravitational waves excited by three different types of perturbations satisfying conservation of total rest mass and angular momentum. These perturbations mimic the pulsar glitch theories i.e., change of moment of inertia due to the star quakes or angular momentum transfer by vortex unpinning at crust-core interface. We carry out numerical hydrodynamic simulations using the pseudo-Newtonian method which makes weak field approximation for the dynamics, but taking all forms of energies into account to compute the Newtonian potential. Unlike other works, we found that the first and second strongest modes that give gravitational waves are $^2p_1$ and $H_1$ rather than$^2f$. We also found that vortex unpinning model excites the inertial mode in quadrupole moment quite effectively. The inertial mode may evolve into the non-axisymmetric r-mode.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.1
• /
• pp.27.4-28
• /
• 2021

Since the first direct detection of the gravitational waves in 2015, more than 50 events coming from the merging of compact binaries composed of black holes and neutron stars have been observed. The simultaneous detection of gravitational waves and electromagnetics waves from the merging of neutron stars opened up multi-messenger astronomy. The forthcoming observations with better sensitivity by the network of ground based detectors will enrich the gravitational wave source populations and provide valuable information regarding stellar evolution, dynamics of dense stellar systems, and star formation history across the cosmic time. The precision of the Hubble constant from the distance measurement of gravitational sources will improve with more binary neutron star events are observed together with the aftweglows. I will also briefly cover the expected scientiic outcomes from the future detectors that are sensitive to much lower frequenies than current detectors.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.1
• /
• pp.27.2-27.2
• /
• 2017

The historic discovery of gravitational waves through direct detection by the LIGO observatories in the USA, in principle, opens up a new window for astronomy. In practice, however, the true launch of gravitational-wave astronomy will await the global array of LIGO like observatories including the planned LIGO-India observatory recently flagged off by the Union cabinet of India. I will review the momentous discovery, the potential of gravitational-wave astronomy and the promise of LIGO-India.