There is a strong evidence that gamma-ray bursters are at the cosmological distances, but there is no rigorous proof yet. The most important question we can ask at this time is: how can one distance scale or another be proven? Note, that all types of objects known to exist in our galaxy are always found in other galaxies as soon as the detectors are sensitive enough to uncover those objects at extragalactic distances. Therefore, we may have full confidence that if the known gamma-ray bursts are associated with our galaxy there should also be gamma-ray bursts associated with M31, which is the nearest giant spiral, pretty much like our own (Atteia & Hurley 1986). This issue cannot be resolved by the BATSE, at least not yet (Hakkila et al. 1994), but a new experiment with times BATSE's sensitivity should resolve the issue (Harrison et al. 1994). If a concentration of very weak bursts towards M31 is detected we shall have to accept the fact that the BATSE bursters are in the corona of our Galaxy, establishing a new type of a distribution of astronomical objects. If no signature of M31 is found we shall have to accept the cosmological origin of the bursts. I hope that all participants of this debate agree with my assessment of the decisive role of the experiment aimed at M31. Note, that extending the observed luminosity function of gamma-ray bursts to the level 10 below the current BATSE limit is almost certain to be interesting in its own right: if the bursters are in the galactic corona we shall find where the corona is truncated; if they are cosmological we shall find them at larger redshifts and they may turn out to be useful for cosmology.
The current situation may be summarized as follows:
It is a great pleasure for me to acknowledge many helpful comments and suggestions by W. H. G. Lewin, R. J. Nemiroff, R. E. Rutledge, K. Z. Stanek and R. A. M. J. Wijers. This work was supported with the NASA grant NAG5-1901.
REFERENCES
Atteia, J. L. et al. 1987, ApJS, 64, 305
Atteia, J. L. \& Hurley, K. 1986, Adv. Space Sci., Vol 6, No. 4, p. 39
Band, D. L. 1994a, ApJ, 422, L75
Band, D. L. 1994b, ApJ, 432, L23
Bessel, F. W. 1838, MNRAS, 4, 152
Clarke, T. E., Blaes, O. \& Tremaine, S. 1994, AJ, 107, 1873
Duncan, R. C. \& Thompson, C. 1992, ApJ, 392, L9
Fenimore, E. E., Epstein, R. I., Ho, C., Klebesadel, R. W. \& Laros, J. 1992, Nature, 357, 140
Fenimore, E. E. et al. 1993, Nature, 366, 40
Fenimore, E. E. Laros, J. G. \& Ulmer, A. 1994, ApJ, 432, 742
Fenimore, E. E. \& Bloom, J. E. 1994, ApJ, submitted
Fenimore, E. E., Klebesadel, R. W. \& Laros, J. G. 1995, preprint
Fishman, G. J. et al. 1978, ApJ, 223, L13
Fishman, G. J. et al. 1994, ApJS, 92, 229
Golenetskii, S. V., Ilyanskii, V. N. \& Mazets, E. P. 1984, Nature, 307, L9
Gould, A. 1992, ApJ, 386, L5
Gregory, P. C. \& Condon, J. J. 1991, ApJS, 75, 1011
Hakkila, J. et al. 1994, ApJ, 422, 659
Harrison, F. A. et al. 1994, Andromeda proposal
Higdon, J. C. \& Lingenfelter, R. E. 1990, ARAA, 28, 401
Hurley, K. et al. 1994, Nature, 372, 652
Jennings, M. C. 1982, ApJ, 258, 110
Jennings, M. C., \& White, R. S. 1980, ApJ, 238, 110
Joss, P. C. \& Rappaport, S. A. 1984, ARAA, 22, 537
Kouveliotou, C. et al. 1987, ApJ, 322, L21
Kouveliotou, C. et al. 1992, The Compton Obs. Sci. Workshop, p. 61, Eds: Shrader, C. R., Gehrels, C. R. \& Dennis, D., NASA
Kulkarni, S. R. et al. 1994, Nature, 368, 129
Lamb, D. Q. 1992, IAP Conf. Proc. 265, 221
Lamb, D. Q. \& Quashnock, J. M. 1994, AIP Conf. Proc., 307, 74
Lestrade, J. P. et al. 1992, A\&AS, 97, 79
Li, H. \& Dermer, C. D. 1992, Nature, 359, 514
Mazets, E. P. 1986, Proc. 19th Internat. Cosmic Conf., Eds: Jones, F. C. et al. (Washington, DC, NASA), p. 424
Mazets, E. P. et al. 1982, Ap. Space Sci., 84, 173
Meegan, C. A., Fishman, G. J., \& Wilson, R. R. 1985, ApJ, 291, 479
Meegan, C. A. et al. 1992, Nature, 355, 143
Messina, D. C. \& Share, G. H. 1992, AIP Conf. Proc., 265, 206
M\'esz\'aros, P., Rees, M. J. \& Papathanassiou, H. 1994, ApJ, 432, 181
Mitrofanov, I. et al. 1994, AIP Conf. Proc. 307, 187
Murakami, T. et al. 1992, AIP Conf. Proc. 265, 28
Murakami, T. et al. 1994, Nature, 368, 127
Nemiroff, R. J. 1994a, AIP Conf. Proc., 307, 730
Nemiroff, R. J. 1994b, Comments on Ap., 17, 4
Nemiroff, R. J. et al. 1994, ApJ, 435, L133
Norris, J. P. et al. 1994, ApJ, 424, 540
Norris, J. P. et al. 1995, ApJ, 439, 542
Ostriker, J. P. 1992, private communication.
Paciesas, W. S. et al. 1992, AIP Conf. Proc., 265, 190
Paczy\'nski, B. 1986, ApJ, 308, L43
Paczy\'nski, B. 1991, Acta Astron., 41, 257
Paczy\'nski, B. 1992a, AIP Conf. Proc., 265, 144
Paczy\'nski, B. 1992b, Nature, 355, 521
Paczy\'nski, B. 1992c, Acta Astron., 42, 145
Paczy\'nski, B. \& Long, K. 1988, ApJ, 333, 694
Palmer, D. M. et al., 1994, ApJ, 433, L77
Piran, T. 1992, ApJ, 389, L45
Podsiadlowski, P., Rees, M. J. \& Ruderman, M. 1995, MNRAS, submitted
Prilutski, O. F. \& Usov, V. V. 1975, Ap. Space Sci., 34, 395
Ruderman, M. 1975, Ann. NY Acad. Sci., 262, 164
Rutledge, R. E. \& Lewin, W. H. G. 1993, MNRAS, 265, L51
Schaefer, B. E. 1992, ApJ, 393, L51
Schaefer, B. E. 1994, ApJS, 92, 285
Schmidt, M., Higdon, J. C., \& Hueter, G. 1988, ApJ, 329, L85
Shklovsky, I. S., \& Mitrofanov, I. G. 1985, MNRAS, 212, 545
Stanek, K. Z., Paczy\'nski, B. \& Goodman, J. 1993, ApJ, 413, L7
Stecker, F. W., De Jager, O. C. \& Salamon, M. H. 1992, ApJ, 390, L49
Tamblyn, P. \& Melia, F. 1993, ApJ, 417, L21
Ulmer, A. \& Goodman, J. 1995, ApJ, 442, 67
van den Berg, S. 1983, Ap. Space Sci., 97, 385
van Paradijs, J. 1995, private communication
Vasisht, G. et al. 1994, ApJ, 431, L35
Wall, J. V. \& Peacock, J. A. 1985, MNRAS, 216, 173
Wijers, R. A. M. J. \& Paczy\'nski, B. 1994, ApJ, 437. L107
Zdziarski, A., Svensson, R. \& Paczy\'nski, B. 1991, ApJ, 366, 343