GCN Circular 408
Subject
GRB990907 and 990908
Date
1999-09-10T20:55:50Z (25 years ago)
From
Brian Schmidt at Res. School of Astro.and Astrophbrian@mso.anu.edu.au <brian@mso.anu.edu.au>
Tim Axelrod, Jeremy Mould and Brian Schmidt (The Research School of
Astronomy and Astrophysics, The Australian National University) report
the following observations of GRB990907 and GRB990908.
We have imaged the position of both GRB990907 and GRB990908 with the
Mount Stromlo 50inch telescope + macho camera at multiple epochs in
approximately 2.4" seeing. A differential image analysis of an area
21'x21' around the BeppoSAX position of GRB990907 (GCN 405) from two
images taken 1999 Sep 8.56 and 1999 Sep 9.60 shows no variable sources
with residuals brighter than a magnitude of m_v=20.3. A similar analysis
of a 21'x21' field centered on the BeppoSAX position of GRB990908
(GCN 406) from images taken 1999 Sep 8.48 and 1999 Sep 9.59 shows a single
variable stellar object (mag approx 18), fading by 0.3 magnitudes,
present at both epochs, and present on the Digital Sky Survey (RA:
06:51:10.52 DEC: -75:02:17.3 J2000). This object is most likely a short
period variable star within our own galaxy, but due to our
poor seeing conditions, it is possible the host could be a compact
galaxy, and is therefore worthy of further investigation. No other sources
were seen with residuals brighter than m_v=20.3.