ESA Science News
http://sci.esa.int

27 Jun 2000

Hubble uncovers the first high-resolution details in a gamma-ray burst
host galaxy

A group of European astronomers have obtained the first detailed images
of a galaxy in which a gamma-ray burst has occurred. The image was taken
with one of the NASA/ESA Hubble Space Telescope`s high-resolution
cameras and reveals a barred spiral galaxy with numerous star-forming
regions. The gamma-ray burst has been located in one such actively star-
forming region. This is a very important step forward in our understanding
of gamma-ray bursts and their immediate surroundings and offers possible
clues to their progenitors.

IMAGE CAPTIONS:

[Image 1: http://sci.esa.int/hubble/news/imagecollection.cfm?&oid=21205]
First high-resolution details in gamma-ray burst host galaxy

These images of the galaxy ESO 184-G82 are the most detailed images of
a gamma-ray burst galaxy ever obtained. They were taken with the Space
Telescope Imaging Spectrograph (STIS) onboard the NASA/ESA Hubble
Space Telescope. The image on the left was taken with the STIS broad-band
"clear" filter. A composite image created using the same broad-band image
(in blue) and an image obtained with the STIS red filter (in red) is shown on
the right and details from this image are shown in the upper right and in
higher detail below right.

These new Hubble observations reveal that the host galaxy is actively star-
forming and contains numerous clouds of hydrogen and regions teeming
with activity from newly born hot stars. The galaxy is a spiral with loosely
wound spiral arms and a large bar of gas and dust running through the centre.

The sharpness of the Hubble Space Telescope`s vision has enabled
astronomers to discover that the gamma-ray burst and the supernova
occurred in an active region in one of the galaxy`s spiral arms. Here an
underlying hydrogen gas complex is overlaid with several bright red giant
stars. At the exact position of the gamma-ray burst (marked with lines on
the lower right image) a very compact source of emission is seen. Most of
this emission is probably the last remnant of the fading light from the
supernova itself, but the scientists suspect that a faint underlying star
cluster may contribute as well.

This is a very important step forward in our understanding of gamma-ray
bursts and their immediate surroundings and offers possible clues to their
progenitors.

The Hubble observations were carried out 12 June 2000. The colour
composite was constructed from two exposures combined in chromatic
order: 1240 seconds through the clear filter (in blue), and 1185 seconds
through a red filter (in red). The fields of view of the three images
clockwise are 45x35 arcseconds, 13x7 arcseconds and 2x2arcseconds.

[Image 2: http://sci.esa.int/hubble/news/image.cfm?oid=21186&ooid=21205]
First close look at gamma-ray burst host galaxy ESO 184-G82

The galaxy ESO 184-G82 was host to a combined gamma-ray burst and
supernova explosion seen first time in 25 April 1998. The galaxy is a barred
spiral of type SBbc which is a loosely wound spiral galaxy with a central bar.
These galaxies are typically star-forming, and this galaxy is no exception. In
its spiral arms large clumps of star-forming regions are visible.

This Hubble observation was carried out 12 June 2000. The field of view of
the image is 45 x 35 arcseconds.