Observations of GRB 970228 and GRB 970508, and the Neutron-Star Merger Model
نویسندگان
چکیده
We present the discovery observations for the optical counterpart of the γ-ray burster GRB 970508 and discuss its light curve in the context of the fireball model. We analyze the HST data for this object, and conclude that any underlying galaxy must be fainter than R = 25.5. We also present a detailed analysis of the HST images of GRB 970228 claimed to show a proper motion of the optical counterpart and conclude that, within the uncertainties, there is no proper motion. We examine several aspects of the neutron-star merger model for γ-ray bursts. In particular, we use this model to predict the redshift distribution of γ-ray bursters, and adopting a recent determination of the cosmic star-formation history, we show that the predicted distribution of logN − logP relation is consistent with that observed for GRBs. Subject headings: γ-rays: bursts — cosmology: observations
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We present the discovery observations for the optical counterpart of the γ-ray burster GRB 970508 and an analysis of its light curve and of the HST imaging data. We also present a detailed analysis of the HST images claimed to show a proper motion of the optical counterpart of GRB 970228 and conclude that, within the uncertainties, there is no proper motion. We examine several aspects of the ne...
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The analysis of the light curves of the optical counterparts of GRB 970228 and GRB 970508 points out remarkable similarities. The spectral distribution obtained from the color indices shows that both the transients became bluer during the increasing stage, and redder after the maximum. A main difference concerns the behaviour of the optical fading which is well fitted by a single power law in t...
متن کاملX iv : a st ro - p h / 97 10 31 3 v 1 2 8 O ct 1 99 7 Did GRB 970228 and GRB 970508 present similar optical properties ?
The analysis of the light curves of the optical counterparts of GRB 970228 and GRB 970508 points out remarkable similarities. The spectral distribution obtained from the color indices shows that both the transients became bluer during the increasing stage, and redder after the maximum. A main difference concerns the behaviour of the optical fading which is well fitted by a single power law in t...
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