HST STIS Images of the Host of XRF/GRB 020427

Above: The field of XRF/GRB 020427 This image shows the majority of the field of view of the STIS 50CCD (open) image. The field is 40" across, North is up, East to the left. The green circle shows the our estimate of the position of the Chandra X-ray counterpart to this burst. The circle overlays one of a complex of three galaxies, which are remarkably similar in magnitude and morphology. The two southern-most of these appear to be connected by a bridge of light.

We believe the combined error in the position of the X-ray transient and the transfer to the HST image is less than 0."45, one-sigma. The XRF appears to lie on a galaxy with V magnitude of ~24.7. This galaxy, which is extended in the NE-SW direction with a total length of ~1."5, has two neighbors within a few arseconds of similar magnitude and morphology, as well as a number of fainter neighbors. The position obtained by Fox et al. places the GRB preferentially towards an end of the galaxy. If we use only the header of the Chandra image to do the alignment, we find a location near a bright knot on the apparent host, about one-sigma from the Fox position. Images taken at a later date could allow a search for an optical counterpart.

Observations of this field have also been undertaken independently at the VLT (see the accompanying GCN 1439, Castro-Tirado et al.). The VLT observations show the complex of the three similar galaxies to be blue, which is consistent with observations of GRB hosts in general (Fruchter et al., Ap J. 519L, 13, 1999).

This result was reported as GCN 1440 .