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Evidence for a late-time outburst of the X-ray afterglow of GB970508 from BeppoSAX

L. Piro·L. Amati·L. A. Antonelli·R. C. Butler·E. Costa·G. Cusumano·M. Feroci·F. Frontera·J. Heise·J. in' t Zand·S. Molendi·J. Muller·L. Nicastro·M. Orlandini·A. Owens·A. N. Parmar·P. Soffitta·M. Tavani
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Abstract

The gamma-ray burst GB970508 was observed simultaneously by the Gamma Ray Burst Monitor (GRBM) and one of the X-ray Wide Field Cameras (WFC) aboard BeppoSAX. The latter provided a position within 1.9' radius. A series of follow-up observations with the Narrow Field Intruments (NFI) was then performed in a period from 6 hours to 6 days after the main event. A previously unknown source, which we associate with the afterglow of the GRB, was discovered in the error box. We find that, after the initial burst, X-ray emission is still present and decays as t^(-1.1) up to 6 times 10^4 s. This is followed by a burst of activity with a duration 10^5 s. The energy produced in this event is a substantial fraction of the total energy of the GRB, which means that the afterglow is not a remnant of the initial burst (the GRB) that fades away smoothly. Our results support the idea that the processes generating the GRB and its afterglow are the same.

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L. Piro, L. Amati, L. A. Antonelli, R. C. Butler, E. Costa, G. Cusumano, M. Feroci, F. Frontera, J. Heise, J. in' t Zand, S. Molendi, J. Muller, L. Nicastro, M. Orlandini, A. Owens, A. N. Parmar, P. Soffitta, M. Tavani. 1998-01-07. Evidence for a late-time outburst of the X-ray afterglow of GB970508 from BeppoSAX. https://arxiv.org/abs/astro-ph/9710355

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