High resolution imaging of the X-ray afterglow of GRB970228 with ROSAT

TL;DR

This paper reports the precise localization of the X-ray afterglow of GRB970228 using ROSAT HRI, confirming its association with the optical transient and analyzing its decay behavior across X-ray energies.

Contribution

It provides the most accurate X-ray afterglow position for GRB970228, establishing the link between X-ray and optical afterglows and presenting a detailed decay light curve.

Findings

X-ray afterglow position matches optical transient within 2''

Decay light curve fits a power-law model

X-ray and higher-energy decay behaviors are consistent

Abstract

We report results of a ROSAT High-Resolution Imager (HRI) observation of the X-ray error box given by the BeppoSAX Wide Field Camera for the gamma-ray burst that occurred on 1997 February 28. The observation started 10 days after the burst and ended three days later, with a total exposure of 34.3 ks. An X-ray source was detected within the 3' WFC error box and its position determined with a 10'' radius accuracy. The source position is in the BeppoSAX Narrow Field Instrument source error box and is coincident (to within 2'') with the optical transient associated with GRB970228. This is the most precise position obtained for an X-ray afterglow and confirms that the X-ray and optical afterglows have the same origin. We present the 0.1--2.4 keV combined HRI and BeppoSAX Low-Energy Concentrator Spectrometer decay light curve which can be well fit with a power-law. The decay is consistent with that measured at higher energies (2--10 keV) with the BeppoSAX Medium-Energy Concentrator Spectrometer.