Tidal love number and its influence on the pericenter shift of S-stars near Sgr A*

Abstract

The tidal love number determines a star's deformability rate in the presence of gravitational potential and depends on the star's internal structure. In this work, we investigate two significant prospects on tidal love number : (i) the influence of the polytropic index of stars on the tidal love number and , (ii) how tidal love number affects the pericenter shift of S-stars near Sgr A* which is an important probe for strong-field tests of gravitational theories. We consider S-stars orbiting Sgr A* at a pericenter distance of 45 au to 500 au, well below the S-2 orbit. The S-stars have polytropic indices of the range, n = 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, and 4.5, and eccentricity, e = 0.9 inclined at $i=90 ^{\circ}$. The tidal love number is estimated for multipole moments $l=2$ and $l=3$. It has been found that the tidal love number decreases as the polytropic index increases. Additionally, the tidal love number for the multipole moment of $l=2$ is dominant over that of $l=3$. The tidal distortion effect also causes a greater pericenter shift in compact orbit S-stars with lower polytropic indices and tidal love number having multipole moment $l=2$. The estimated results offer relevant insights for testing general relativity and its alternative theories in the vicinity of Sgr A*