An independent estimate of the cosmological distance to GRB970228

Assuming binary neutron star mergings as a model for GRBs, an independent estimate is given for the redshift of GRB970228 using mean statistical properties of GRBs observed by BATSE. We derive z = 0.7 ± 0.1 depending on the power-law index of the GRB spectrum s = −1.1 ± 0.3 and the value of the redshift of the initial star formation z ∗ = 3 − 10 in a flat Ω = 1 Universe with a cosmological term Λ = 0.7. A faint optical transient object (Groot et al. 1997a) has been found within gamma-ray and X-ray error boxes of GRB970228. Deep optical studies of this field with large telescopes revealed an elongated faint (R ≃ 24) object coincident with the optical transient position (Groot et al. 1997b; Metzger et al. 1997b). X-ray spectra of the X-ray transient source accompanied GRB970228, obtained by BeppoSAX (Costa et al. 1997b), display soft X-ray absorption corresponding to the column density toward the source NHI = 1.6 × 10 21 cm −2 (which is in agreement with the galactic absorption in this direction of 1.44 × 10 21 cm −2;