GRB 000418



Discovery of the NIR afterglow of GRB 000418



S. Klose, B. Stecklum (Thüringer Landessternwarte Tautenburg),
O. Fischer (Universitäts-Sternwarte Jena),
J. Gorosabel (DSRI, Copenhagen),
C. Sanchez-Fernandez (LAEFF-INTA, Madrid),
A. Castro-Tirado (LAEFF-INTA, Madrid, and IAA-CSIC, Granada),
D. Butler (Max-Planck-Institut für Extraterrestrische Physik, Garching),
S. Hippler, Th. Ott, M. Kasper, R. Weiss (Max-Planck-Institut für Astronomie, Heidelberg),
L. Montoya, A. Aguirre (Max-Planck-Institut für Astronomie, Heidelberg, and Calar Alto observatory),
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),
D. H. Hartmann (Clemson University, Clemson), and
J. Greiner (AIP Potsdam)

report:



The central part of the error box of GRB 000418 (Hurley et al., GCN 642) was imaged with the Calar Alto 3.5-m telescope on April 20, 20:55 UT - 21:54 UT, using the near-infrared camera Omega Cass. The limiting magnitude of the K'-band image is about K'=18 after adding all images taken at different position angles of a wire-grid polarizer. A second observing run was performed on April 22, 02:22 UT - 03:23 UT, using the same telescope and the same instrumentation. The same region of the error box was also covered by K'-band (April 20, 22:06 UT - 22:46 UT and April 24, 21:36 UT - 22:30 UT) and J-band images (April 21, 22:23 UT - 22:48 UT) taken with the Calar Alto 1.23-m telescope using the near-infrared camera MAGIC. Additional frames covering the whole error box (Hurley et al. GCN #642) are being processed and the results will be reported soon.

A comparison between the April 20 and April 22 (Fig. 2) images and a cross-check with the 1.23-m images has revealed a potentially fading source within the central GRB error box at RA, DEC (J2000) = 12:25:19.3, 20:06:12 (+/- 1 arcsec). This source (K' ~ 16) is visible on the 3.5-m and 1.23-m frames obtained during the first night. It has no counterpart on the corresponding DSS2-red image. Since standard stars are not available at the moment we can only provide a rough estimate of the brightness of the source.




Figure 1: DSS2 red image of the error box of GRB 000418 and the area covered by the 3.5-m observations.



Figure 2: Part of the K'-band image of the error box of GRB 000418 (Fig. 1).



Any use of these data should be accompanied by a reference.


S. Klose and B. Stecklum, Thüringer Landessternwarte Tautenburg.



Last modified: April 29, 2000