6 research outputs found
Observable form of pulses emitted from relativistic collapsing objects
In this work, we discuss observable characteristics of the radiation emitted
from a surface of a collapsing object. We study a simplified model in which a
radiation of massless particles has a sharp in time profile and it happens at
the surface at the same moment of comoving time. Since the radiating surface
has finite size the observed radiation will occur during some finite time. Its
redshift and bending angle are affected by the strong gravitational field. We
obtain a simple expression for the observed flux of the radiation as a function
of time. To find an explicit expression for the flux we develop an analytical
approximation for the bending angle and time delay for null rays emitted by a
collapsing surface. In the case of the bending angle this approximation is an
improved version of the earlier proposed Beloborodov-Leahy-approximation. For
rays emitted at the accuracy of the proposed improved approximations
for the bending angle and time delay is of order (or less) than 2-3%. By using
this approximation we obtain an approximate analytical expression for the
observed flux and study its properties.Comment: 13 pages, 10 figures;Typos in equations and refrences are corrected.
No change in the results and discussion