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GCN Circular 446

GRB991106, near-infrared observations
1999-11-12T18:07:58Z (25 years ago)
Sylvio Klose at TLS Tautenburg <>
B. Stecklum, S. Klose (Thueringer Landessternwarte Tautenburg), 
O. Fischer (Universitaets-Sternwarte Jena),
R. Lenzen (Max-Planck-Institut fuer Astronomie, Heidelberg),
F. J. Vrba, A. A. Henden, C. B. Luginbuhl,
   B. Canzian, S. E. Levine, H. H. Guetter, J. A. Munn
   (U.S. Naval Observatory, Flagstaff),
A. Castro-Tirado (LAEFF-INTA, Madrid, and IAA-CSIC, Granada), 
J. Greiner (AIP Potsdam), 
J. Gorosabel (LAEFF-INTA, Madrid, and University of Amsterdam), and
A. Riffeser (Universitaets-Sternwarte Muenchen) 


The error box of GRB 991106 was imaged with the Calar Alto 3.5-m
telescope on November 7.799 - 7.841 UT using the near-infrared camera 
Omega Cass (see The frames were
taken in the course of a project whose goal is to measure the degree of
linear polarization of GRB afterglows (Klose et al., proceedings 5th
Huntsville symposium, to be submitted). The limiting magnitude of the
K'-band image is about K'=19 after adding all images taken at
different position angles of the wire-grid polarizer. Since the
error box is at low Galactic latitude, we report here on the results 
of a search for very red objects. Polarimetric data will be published 
at later times.

A comparison of the combined K'-band image with I-band images obtained
on November 7.9 UT at the  Calar Alto 1.23-m telescope and on November
8.2 at the USNO 1.0-m telescope shows an object at coordinates RA
(J2000) = 22:24:32.4, DEC = 54:23:51 (+/- 1 arcsec) which has a large
I-K' color. The object is inside the original 3.2 arcmin BeppoSAX
error circle (Piro et al., GCN #435), but about 10 arcsec outside the
BeppoSAX NFI 1.5 arcmin error circle (Antonelli et al., GCN
#445). There is one object inside the NFI error circle which is seen
both in K' and I, and which is very red. This object is at RA (J2000)
= 22:24:39.7, DEC = 54:21:46 (+/- 1 arcsec). Both objects have very
faint counterparts on the DSS2 Digitized Sky Survey. They seem to be 
constant between the two I-band epochs. This cannot be stated with 
certainty, however.

There is no object visible in K' at the position of the radio source
reported by Frail et al. (GCN #444). Any such source must be fainter than
about K'=19.

The preliminary K'-band image is posted on the Tautenburg Web page at

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