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16 papers · 1 filter
General formulae for the periapsis shift of a quasi-circular orbit in static spherically symmetric spacetimes and the active gravitational mass density
Tomohiro Harada, Takahisa Igata, Hiromi Saida +1
We study the periapsis shift of a quasi-circular orbit in general static spherically symmetric spacetimes. We derive two formulae in full order with respect to the gravitational fi…
Periapsis shifts in dark matter distribution around a black hole
Takahisa Igata, Tomohiro Harada, Hiromi Saida +1
We consider the periapsis shifts of bound orbits of stars on static clouds around a black hole. The background spacetime is constructed from a Schwarzschild black hole surrounded b…
A Significant Feature in the General Relativistic Time Evolution of the Redshift of Photons Coming from a Star Orbiting Sgr A*
Hiromi Saida, Shogo Nishiyama, Takayuki Ohgami +16
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 relativist…
Null Geodesics and Repulsive Behavior of Gravity in (2+1)-dimensional Massive Gravity
Keisuke Nakashi, Shinpei Kobayashi, Shu Ueda +1
We study the null geodesics in a static circularly symmetric (SCS) black hole spacetime which is a solution in the -dimensional massive gravity proposed by Bergshoeff, Hohm…
Spherical polytropic balls cannot mimic black holes
Hiromi Saida, Atsuhito Fujisawa, Chul-Moon Yoo +1
The so-called black hole shadow is a dark region which is expected to appear in a fine image of optical observation of black holes. It is essentially an absorption cross section of…
Maximum mass of a barotropic spherical star
Atsuhito Fujisawa, Hiromi Saida, Chul-Moon Yoo +1
The ratio of total mass to surface radius of spherical perfect fluid ball has an upper bound, . Buchdahl obtained under the assumptions; non-increasing m…