Scalar field effects on the orbit of S2 star

Abstract

Precise measurements of the S-stars orbiting SgrA* have set strong constraints on the nature of the compact object at the centre of the Milky Way. The presence of a black hole in that region is well established, but its neighbouring environment is still an open debate. In that respect, the existence of dark matter in that central region may be detectable due to its strong signatures on the orbits of stars: the main effect is a Newtonian precession which will affect the overall pericentre shift of S2, the latter being a target measurement of the GRAVITY instrument. The exact nature of this dark matter (e.g. stellar dark remnants or diffuse dark matter) is unknown. This article assumes it to be a scalar field of toroidal distribution, associated with ultralight dark matter particles, surrounding the Kerr black hole. Such a field is a form of ‘hair’ expected in the context of superradiance, a mechanism that extracts rotational energy from the black hole. Orbital signatures for the S2 star are computed and shown to be detectable by GRAVITY. The scalar field can be constrained because the variation of orbital elements depends both on the relative mass of the scalar field to the black hole and on the field mass coupling parameter.

Precessing and periodic motions around a black-bounce/traversable wormhole

“…It is no doubt that the anomalous perihelion advance of Mercury belongs to the earliest observational evidences of GR [32] and its next-to-leading-order advance has been examined as well [33][34][35]. Nowadays, the periastron advances of the planets around the Sun [36][37][38][39][40][41][42][43] and other stars [44][45][46][47], of binary stars [48][49][50][51][52][53][54] and of stars around the supermassive black hole in the Galactic Center Sgr A* [55][56][57][58][59][60][61][62][63][64] have been widely adopted and discussed for probing and constraining modified theories of gravity and new physics. Especially, the Schwarzschild precession in the orbit of the star S2 orbiting Sgr A* predicted by GR was just detected by the interferometry GRAVITY [64], paving the way for testing the fundamental theories of gravity and investigating the properties of Sgr A* by making use of the precessing motion of geodesic orbits around various kinds of black holes and other spacetimes.…”

Probing a black-bounce-Reissner–Nordström spacetime with precessing and periodic motion

“…Since the advance of the perihelion of Mercury becomes one of the earliest evidences of the general relativity [50], precessing orbits have been a promising tool for testing alternative theories of gravity. The precessing motion in various gravitational fields, such as those of the planets around the Sun [51][52][53][54][55][56][57][58][59][60][61][62][63][64], of the exoplanets around other stars [65][66][67][68], of the binary pulsars [69][70][71][72][73][74] and of the stars around Sgr A* [75][76][77][78][79][80][81][82][83][84], have also been investigated intensively. In particular, the detection of the Schwarzschild precession of S2 around Sgr A* by GRAVITY [84] lays the observational foundation for testing the theories of gravitation and detecting new physics in the surroundings of the supermassive black hole.…”

Dark energy interactions near the galactic centre

“…It is known that there is a relativistic, compact object in the galactic centre; the black hole SgrA * . The stars orbiting SgrA * are called the S-stars [62][63][64][65][66][67][68][69]. A large fraction of these stars have orbits with high eccentricities.…”