Electronic Telegram No. 36
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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XTE J1811-197
     C. B. Markwardt, University of Maryland and Goddard Space Flight
Center (GSFC), A. I. Ibrahim (GSFC, The George Washington University),
and J. H. Swank (GSFC), report:  "Based on reports from the IPN and HETE
of renewed bursting activity by the soft gamma repeater SGR 1806-20 (GCN
2297, 2308), an RXTE PCA pointed observation was undertaken, which
revealed unexpected X-ray pulsations at a period of 5.54 s in the PCA
field of view (GCN 2306).  We obtained an RXTE PCA scanning observation
Jul 18.23-18.27 (UT).  A new source was detected, whose position is,
R.A. = 18h10.9m, Decl. = -19o42' (equinox 2000.0), with estimated 99%
confidence semi-major axes of 5' in R.A. and 7' in Decl. This confidence
region excludes both the reported IPN burst annuli and the HETE burst
error region, and is not consistent with any other known pulsar.  The
pulsations are clearly from this source, which we designate XTE
J1811-197.  The fitted flux was 2.5 +/- 0.2 mCrab (2-10 keV).  On
hindsight, XTE J1811-197 has been detectable in RXTE PCA galactic bulge
scans since Feb 7, 2003 (but not before), and it is steadily declining
from a maximum of 3.6 mCrab.  Follow-up observations are encouraged."


NOTE: These 'Central Bureau Electronic Telegrams' are intended to
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                         (C) Copyright 2003 CBAT
2003 July 25                      (CBET 36)               Kyle E. Smalley