AGN and starburst coexistence in the short GRB100628A host galaxy.

We have modelled the line ratios and the continuum spectral energy distribution (SED) of the short gamma-ray burst GRB100628A host galaxy complex. The results suggest that an active galactic nucleus (AGN) and a star-burst (SB) coexist in Nicuesa Guelbenzu et al.'s 'galaxy C'. The AGN spectrum is explained by a relatively strong flux. Two of the observed regions (blobs) are located in the ISM, outside the AGN photoionization cones. The strongest Hb line flux calculated by a SB dominated model was found in the tidal tail of galaxy C, while the strongest Hb line flux calculated by an AGN dominated model was found in the galaxy C bulk. O/H element abundances are near solar everywhere, while N/H spans a factor of ~10. The radio data have different origins, thermal bremsstrahlung and reprocessed radiation by dust. The infrared-optical photometric data measured from Nicuesa Guelbenzu et al.'s 'galaxy D', located outside the X-ray telescope (XRT) error circle, are reproduced by a black-body flux at 3000 K. This flux may represent the radiation of the underlying old star population observed throughout the SED in the infrared. AGNs in other SGRB hosts are investigated.