## 6. Nonzero gravitational redshiftPhotons emitted from the surface of a neutron star lose part of their energy and change the rate at which they appear, while escaping to infinity. This is a general relativistic effect which is important in the extremely strong gravitational potential near neutron star. In case of nonrotating neutron star, all the corrections to observables are given by simple scalar factors (Thorne 1977). The emerging spectrum of a star is squezeed along frequency axis, when measured at infinity (near the Earth). All photons decrease their initial frequency to , and where is measured by a distant observer, and
Consider an arbitrary phase of a burst. If the redshift factor is
guessed and the observed energy spectrum has been corrected for that
factor, then the fitting procedure yields directly estimates of
and in the photosphere
at that phase. Both and
yield mass to luminosity ratio, . In case if
Lewin et al. (1993) review also independent methods, which can be used for the estimates of . © European Southern Observatory (ESO) 1997 Online publication: July 3, 1998 |