A Significant Feature in the General Relativistic Time Evolution of the
  Redshift of Photons Coming from a Star Orbiting Sgr A*
  The star S0-2, orbiting the Galactic central massive black hole candidate Sgr
A*, passed its pericenter in May 2018. This event is the first chance to detect
the general relativistic (GR) effect of a massive black hole, free from
non-gravitational physics. The observable GR evidence in the event is the
difference between the GR redshift and the Newtonian redshift of photons coming
from S0-2. Within the present observational precision, the 1st post-Newtonian
(1PN) GR evidence is detectable. In this paper, we give a theoretical analysis
of the time evolution of the 1PN GR evidence, under a presupposition that is
different from used in previous papers. Our presupposition is that the
GR/Newtonian redshift is always calculated with the parameter values (the mass
of Sgr A*, the initial conditions of S0-2, and so on) determined by fitting the
GR/Newtonian motion of S0-2 with the observational data. It is then revealed
that the difference of the GR redshift and the Newtonian one shows two peaks
before and after the pericenter passage. This double-peak-appearance is due to
our presupposition, and reduces to a single peak if the same parameter values
are used in both GR and Newtonian redshifts as considered in previous papers.
In addition to this theoretical discussion, we report our observational data
obtained with the Subaru telescope by 2018. The quality and the number of
Subaru data in 2018 are not sufficient to confirm the detection of the
double-peak-appearance.
