The X-ray, optical and infrared counterpart to GRB 980703

¹ Astronomical Institute "Anton Pannekoek”, University of Amsterdam, & Center for High Energy Astrophysics, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
² Astrophysics Division, Space Science Department of ESA, European Space Research and Technology Centre, 2200 AG Noordwijk, The Netherlands
³ Joint Astronomy Centre, 660 N. A'ohoku Place, Hilo, Hawaii 9672 0, U.S.A.
⁴ Physics Department, University of Alabama in Huntsville, Huntsville AL 35899, U.S.A.
⁵ Universities Space Research Association
⁶ NASA/MSFC, Code ES-84, Huntsville AL 35812, U.S.A.
⁷ Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
⁸ Istituto Tecnologie e Studio Radiazioni Extraterrestri (TESRE), CNR, Via P. Gobetti 101, 40 129 Bologna, Italy

Received: 29 December 1998
Accepted: 10 March 1999

Abstract

We report on X-ray, optical and infrared follow-up observations of GRB 980703. We detect a previously unknown X-ray source in the GRB error box; assuming a power law decline we find for its decay index . We invoke host galaxy extinction to match the observed spectral slope with the slope expected from "fireball” models. We find no evidence for a spectral break in the infrared to X-ray spectral range on 1998 July 4.4, and determine a lower limit of the cooling break frequency:  Hz. For this epoch we obtain an extinction of . From the X-ray data we estimate the optical extinction to be A_V =, inconsistent with the former value. Following Wijers & Galama (1998), we determine intrinsic fireball properties for this burst.