If GRB afterglow is produced by interaction of a relativistic shock wave with the interstellar medium (Mészáros & Rees 1992), the afterglows in elliptical galaxies should be dimmer than in the spirals where the interstellar medium is more dense. Present observations of GRB afterglows show that approximately 1/4 of the bursts with good localization do not have detectable X-ray afterglows, which is consistent with the expected fraction of GRB in elliptical galaxies.
Our model predicts an increase of relative number of the GRB in elliptical galaxies at high redshifts. A direct observational detection of an elliptical host galaxy of a GRB is desirable to support the binary model of GRB.
The authors are grateful to the conference organizers for the financial support which made their participation in the conference possible. This research was carried out under the support of INTAS project No. 96-0315 and the RFBR grant No. 98-02-16801.
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