**Publication date:** Jul 2011

**Abstract:**

We study gravitational redshift of photons and neutrinos radiated by the

braneworld neutron or quark stars that are considered in the framework

of the simple model of the internal spacetime with uniform distribution

of energy density, and the external spacetime described by the

Reissner-Nordström geometry characterized by the braneworld

„tidal“ charge b. For negative tidal charges, the external spacetime

is of the black-hole type, while for positive tidal charges, the

external spacetime can be of both black-hole and naked-singularity type.

We consider also extremely compact stars allowing existence of trapped

null geodesics in their interior. We assume radiation of photons from

the surface at radius R, neutrinos from the whole compact star interior,

and their motion along radial null geodesics of the spacetime. In

dependency on the compact stars parameters b and R, the photon surface

redshift is related to the range of the neutrino internal redshift and

the signatures of the tidal charge and possible existence of extremely

compact stars are discussed. When both surface (photon) and internal

(neutrino) redshift are given by observations, both compact star

parameters R and b can be determined in the framework of our simple

model.

**Authors:**

Hladík, Jan; Stuchlík, Zdeněk;