GRB 970828



Near-Infrared and optical follow-up Observations



In IAU Circular 6756 we write:

"The GRB error box was surveyed down to K' = 20 with the Calar Alto 3.5-m telescope on Sept. 9.8 UT using the MAGIC near-infrared camera (0.81" pixels). A comparison with R and I-band images obtained with the prime focus CCD camera of the Tautenburg Schmidt telescope on Aug. 30.9, 31.9, Sept. 1.9, and 6.9 UT and with R-band images taken by Stanek et al. (IAUC 6735) and by Howk et al. (3.5-m WIYN telescope, see http://www.noao.edu/noao/grb/970828.html) shows that all but one object visible in K' within the revised ASCA error circle (IAUC 6732) have a counterpart in R and/or I down to R = 22-23 and I = 20. This object at R.A. = 18h08m30s.52, Decl. = +59o18'49".4 (+/- 1", equinox 2000.0) is notably fainter. Its magnitudes are R = 23-24 (?) and K' = 19.0 +/- 0.4. Since no variable was found in the error box down to R = 24.5 (Odewahn et al., IAUC 6735), we guess, however, that we have not detected the GRB afterglow and constrain its K' magnitude 12 days after the burst to be > 20. Images are available via http://www.tls-tautenburg.de/research/research.html."


The following figures supplement this message.




Left: I-band image taken on 1997, Aug. 31.9 UT using the prime focus CCD camera on the 1.34-m Schmidt telescope of the Thüringer Landessternwarte Tautenburg. Right: K'-band image taken on Sept. 9.8 UT, Calar Alto Observatory, Spain, using the 3.5-m telescope equipped with the MAGIC near-infrared camera (wide-field mode, 0.81" pixels). The circle approximately represents the ASCA error circle (radius 30 arcsec) reported by Murakami et al. (IAUC 6732). The object mentioned in our IAU Circular is indicated. Note that the I-band image is slightly affected by a bad sky flat. The limiting magnitude of this image is about I = 20. The K'-band image was reduced using a special sampling technique, resulting in a pixel scale of 0.4" per pixel.


Any use of these data should be accompanied by a reference to our message in IAUC 6756.


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



This page is maintained by S. Klose (klose@tls-tautenburg.de).

Last modified: October 9, 1997