The optical contents of the IPN1 localization of GRB 790325b: The discovery of a probable QSO association

We report the results of the deepest imaging survey yet carried out of the IPN1 localization of gamma-ray burst (GRB) 790325b. While this is one of th e smallest of the IPN1 GRB localizations, it has been previously surveyed o nly to shallow limits because of the nearby bright (V = 4.97) star 104 Herc ulis. We have used a camera with a 9 mag neutral density region in front of a Tek 2048(2) CCD to apodize the light of 104 Her and allow deep UBVI imag ing of the localization. The observations, obtained at the US Naval Observa tory 1.55 m telescope to a detection limit of V approximate to 22.9, reveal 20 objects clearly within or at the edge of the localization. Near the cen ter of the localization is a QSO candidate that is unlikely (approximate to 97% confidence) to be a random occurrence based on known QSO statistics. C ombining these new statistics with earlier summed statistics linking QSOs/b lue galaxies with IPN1 localizations yields a marginal (approximate to 96% confidence) overall correlation. We also compare our observational results for this field with another recent imaging survey of GRB 790325b based on H ST data and discuss the differences in the results.