Achievements & Publications

Angular Momentum Transport in Early-formed Objects by Cosmic Background Radiation: Radiation-hydrodynamical Approach

Image

Tsuribe, Tohru,   Umemura, Masayuki

The effects of radiation force by the cosmic background radiation (CBR) on early-formed objects shortly after the cosmological recombination are explored. In particular, we are interested in the angular momentum transport in massive disks that originate from tidally spun-up density fluctuations. The radiation force by the CBR is calculated by...

Self-Similar Viscous Collapse of a Self-Gravitating, Polytropic Gas Disk

Image

Mineshige, Shin,   Nakayama, Kunji,   Umemura, Masayuki

Self-similar solutions for the time evolution of polytropic, self- gravitating viscous disks is found on the condition that the kinematic viscosity is nu åisebox-0.5ex~ r(\l\ and the gas pressure is P \i̊sebox-0.5ex~ rho (Gamma ) , where l and Gamma are free parameters, r is radius, and rho is density....

Very Strong Microlensing of Distant Luminous Stars by Relic Massive Black Holes

Image

Turner, Edwin L.,   Umemura, Masayuki

We examine the possibility that a population of relic massive black holes, perhaps constituting an important component of the dark matter, might be indirectly detected via their occasional very strong gravitational lensing of individual luminous stars in distant external galaxies. For plausible, and in some respects conservative, values of the...

Self-similar Collapse of a Self-gravitating Viscous Disk

Image

Mineshige, Shin,   Umemura, Masayuki

A self-similar solution for time evolution of isothermal, self- gravitating viscous disks is found under the condition that \ensuremathα' \ensuremath≡ \ensuremathα(H/r) is constant in space (where \ensuremathα is the viscosity parameter and H/r is the ratio of a half-thickness to the radius of the disk). This solution describes a homologous...

Image

Angular Momentum Transport in Early-formed Objects by Cosmic Background Radiation: Radiation-hydrodynamical Approach

Tsuribe, Tohru,   Umemura, Masayuki

The effects of radiation force by the cosmic background radiation (CBR) on early-formed objects shortly after the cosmological recombination are explored. In particular, we are interested in the angular momentum transport in massive disks that originate from tidally spun-up density fluctuations. The radiation force by the CBR is calculated by...

September 1997   The Astrophysical Journal
Image

Self-Similar Viscous Collapse of a Self-Gravitating, Polytropic Gas Disk

Mineshige, Shin,   Nakayama, Kunji,   Umemura, Masayuki

Self-similar solutions for the time evolution of polytropic, self- gravitating viscous disks is found on the condition that the kinematic viscosity is nu åisebox-0.5ex~ r(\l\ and the gas pressure is P \i̊sebox-0.5ex~ rho (Gamma ) , where l and Gamma are free parameters, r is radius, and rho is density....

August 1997   Publications of the Astronomical Society of Japan
Image

Very Strong Microlensing of Distant Luminous Stars by Relic Massive Black Holes

Turner, Edwin L.,   Umemura, Masayuki

We examine the possibility that a population of relic massive black holes, perhaps constituting an important component of the dark matter, might be indirectly detected via their occasional very strong gravitational lensing of individual luminous stars in distant external galaxies. For plausible, and in some respects conservative, values of the...

July 1997   The Astrophysical Journal
Image

Self-similar Collapse of a Self-gravitating Viscous Disk

Mineshige, Shin,   Umemura, Masayuki

A self-similar solution for time evolution of isothermal, self- gravitating viscous disks is found under the condition that \ensuremathα' \ensuremath≡ \ensuremathα(H/r) is constant in space (where \ensuremathα is the viscosity parameter and H/r is the ratio of a half-thickness to the radius of the disk). This solution describes a homologous...

May 1997   The Astrophysical Journal