Swift uncovers that SAX J0840.7+2248 is not an X-ray Binary, but BeppoSAX X-ray Rich GRB 980429

TL;DR

This paper reports that the source previously thought to be an X-ray binary is actually a long, X-ray rich gamma-ray burst, based on Swift/XRT observations and follow-up analysis.

Contribution

It reveals the true nature of SAX J0840.7+2248 as a gamma-ray burst, correcting prior classification based on new Swift/XRT data.

Findings

SAX J0840.7+2248 is not an X-ray binary.

The source is identified as GRB 980429.

The paper details properties from prompt to late follow-up.

Abstract

During our Swift/XRT program to obtain X-ray positions at arcsecond level for a sample of Galactic X-ray binaries, we discovered that SAX J0840.7+2248 is not a binary, but rather BeppoSAX/WFC+GRBM X-ray Rich GRB 980429. Here we report on this discovery and on the properties of this long, X-ray rich gamma-ray burst, from prompt to (very) late followup.