TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  2607
SUBJECT: SGR 1806-20, potential NIR counterpart
DATE:    04/06/08 11:56:28 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>

C. Kouveliotou (NASA/MSFC),
S. Klose (Thuringer Landessternwarte Tautenburg),
S. Wachter (Spitzer Science Center),
P. Woods (USRA, NASA/MSFC),
S. Patel (USRA, NASA/MSFC),
J. Greiner (MPE Garching),
B. Stecklum (Thuringer Landessternwarte Tautenburg), and
M. van der Klis (University of Amsterdam)


report:


Following the recent activiation in X-rays of SGR 1806-20, we
triggered a Target of Opportunity Observation of the source at ESO
with VLT/ISAAC. Observations were performed in the Ks band on May 28,
6:24 UT - 6:50 UT. Altogether 14 images were taken, 1 min integrated
exposure time each. For the final data analysis we used those images
with the best seeing (8 of the 14 images).

Within the 0.7 arcsec Chandra error circle as reported by Eikenberry
et al. (ApJ 563, L133; their figure 3d), we identify an isolated point
source with Ks = 19.6 +/- 0.4. This source might match the position of
source 'B' in Eikenberry et al., while their source 'A', which is at the
edge of the Chandra error circle, is resolved into at least two
components. We tentatively identify either object B or the second
component of object A as the potential K-band counterpart of SGR 1806-20.
However, further observations are needed during quiescence of the SGR to
determine whether one of the two sources is variable in order to firmly
establish a connection with SGR 1806-20.

We are deebly indebted the ESO staff at Paranal, in particular Poshak
Gandhi, for performing the observations.


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