GRB 991106



Near-infrared observations of the error box of GRB 991106



B. Stecklum, S. Klose (Thüringer Landessternwarte Tautenburg),
O. Fischer (Universitäts-Sternwarte Jena),
R. Lenzen (Max-Planck-Institut für 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 (Universitäts-Sternwarte München) report:



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 http://www.mpia-hd.mpg.de/ ). 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 = 54:23:52 (+/- 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.






K'-band image of the GRB 991106 error box. The two objects mentioned in the text are indicated.



Last modified: November 12, 1999