**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;