GWs from S-stars Revolving Around SMBH at Sgr A*

Abstract

A preliminary estimation of gravitational waves (GWs) from the extreme-mass-ratio-inspirals (EMRIs) system in the Galactic Centre (GC) is given for the 37 observed S-stars revolving around the supermassive black hole (SMBH) at Sagittarius (Sgr) A*. Within this century, the total strain of the gravitational waveform calculated from the post-Newtonian (PN) method with eccentricity is well below the current planned sensitivity of pulsar-timing-array (PTA). New technology might be required in order to extract GW signal from this EMRIs system for future PTA detections.

Gravitational Waves from Accreting Sources

“…The observational evidence for Sgr A * is given by the orbits of the S-stars, that are examples of Extreme Mass Ratio Inspiral (EMRI) events. Being not compact, the S-stars undergo tidal disruption, but their gravitational emission during the inspiral stage can be detected with Pulsar Timing techniques [33]. The properties of 37 S-stars orbiting Sgr A * have been presented by [46].…”

“…The properties of 37 S-stars orbiting Sgr A * have been presented by [46]. The work by [33] estimates the gravitational waveforms, with frequencies of the order of nanoHz and amplitudes in the range 10 −20 -10 −19 , about five orders of magnitude below the sensitivity of current and planned Pulsar Timing Arrays.…”

Gravitational waves from accreting systems

“…Searches for persistent gravitational waves from the Galactic center have been performed with the initial [2] and advanced LIGO interferometers [12], [13], setting upper limits of the order of 10 −25 . The S-stars are examples of Extreme Mass Ratio Inspiral (EMRI) systems that undergo tidal disruption during the inspiral stgae, with a gravitational emission in the range that is investigated with Pulsar Timing techniques [33]. The properties of 37 S-stars orbiting Sgr A * have been presented by [46].…”

“…The properties of 37 S-stars orbiting Sgr A * have been presented by [46]. The gravitational waveforms of S-stars orbiting Sgr A * [33] have frequencies in the nanoHz range and amplitudes in the range 10 −20 -10 −19 , some orders of magnitude below the sensitivity of current and planned Pulsar Timing Arrays.…”

Gravitational redshift/blueshift of light emitted by geodesic test particles, frame-dragging and pericentre-shift effects, in the Kerr–Newman–de Sitter and Kerr–Newman black hole geometries

“…Moreover, we derive novel exact expressions for the frame dragging effect for particles in spherical, non-equatorial orbits in KNdS and KN black hole geometries. These results could be of interest to the observational astronomers of the Galactic centre [13,14,16,17] whose aim is to measure experimentally, the relativistic effects predicted by the theory of General Relativity [28,[56][57][58][59][60][61][62][63][64][65][66][67][68] for the observed orbits of short-period stars-the so called S-stars in our Galactic centre. During 2018, the close proximity of the star S2 (S02) to the supermassive Galactic centre black hole allowed the first measurements of the relativistic redshift observable by the GRAVITY collaboration [69] and the UCLA Galactic centre group whose astrometric measurements were obtained at the W.M.…”