What did ASCA see in the GRB 970828 afterglow?

¹ The Institute of Physical and Chemical Research, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan
² Institute of Space and Astronautical Science, 3-1-1, Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan

Send offprint request to: A. Yoshida

Received: 21 January 1999
Accepted: 5 July 1999

Abstract

The ASCA satellite made a quick followup observation of GRB 970828 and detected its fading X-ray afterglow at the position localized by the All-Sky Monitor on the Rossi XTE satellite. Because of the quickness, the afterglow was still rather bright ( ergs cm^-2 s^-1: 2-10 keV), and ASCA obtained the data of good quality. We found the spectral features of the absorption which implies a column density of  cm^-2 at , together with an emission line at  keV. The line could be red shifted Fe K line. Hence, it suggests a relatively small red shift for this GRB.