Our search is more general than those of Kippen et al. (1998) and Wang & Wheeler (1998): we consider all known SNe without any restriction since any limitation would be in contrast with the main goal of our study (search for possible unrecognized OAs of GRBs in the sample of detected SNe). It should be also noted that the observed SNe, like GRBs, shows an isotropic sky distribution (Fig. 1). The study of Kippen et al. (1998) is restricted to brighter events only (brighter than mag 17) but this is in contrast with BeppoSAX OA statistics (their peaks are below 17 mag in all detected 7 cases) while Wang and Wheeler (1998) restrict to SNe of known Ia, Ib types (but the OA may be also among weak and unclassified SNe).
The statistical significance of the results of cross-correlations between the GRBs and SNe is affected and limited by the following: (1) the positional uncertainty of a quite large fraction of the GRBs is rather high (2) the dates of SN peaks are unknown in most cases (3) the results of optical SNe searches do not represent a full and homogeneous sample so that many (and even a large majority) of the SNe may be missed especially at faint magnitudes (4) there is no systematic sky patrol survey at magnitudes below 15.
For the correlations found, most of the related SNe represent poorly investigated events with poorly known (and in many cases even completely unknown) light curves, decline rates, color indices and no or limited spectral information hence the decision whether they could be related to the GRBs in question is difficult. The recent detections of faint OA of GRBs strongly support and justify further more extended and more complete searches for faint new and variable optical objects especially at low magnitudes (18 and less).
Some of this information can be retrieved from deep archival plates (some of the archival plate collections reach the limiting magnitudes of 20 and even 23 such as ROE Edinburgh and TLS Tautenburg) but a systematic deep CCD patrol could provide more precise and much more complete database.
The work has been supported by the Projects of the Czech Ministry for Education and Youths, Nos. ES02 and ES036.
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