MBCAA Observatory

GRB060403: Search for an optical transient

Observed: 4 April 2006

M. Bonnardeau
5 April 2006


No optical counterpart for this gamma ray burst, down to mag 17.2, 14.9 hours after the event.


The gamma ray burst GRB060403 was detected by the Swift satellite. The burst is of the long type with a 15-150keV fluence of 1.4E-6erg/cm2; the uncertainty on the coordinates is +/-1.1' (Tueller et al (2006) GCN Circular 4948).


The error box was observed with a 203 mm f/6.3 SC telescope with a Clear filter and a SBIG ST7E camera (KAF401E CCD), between 04:01UT and 04:15UT, that is 14.9h after the burst. Three 200s images were obtained with a 2x2 binning, and stacked.

The resulting image is analysed with the AstroMB program:

  • 471 sources are detected with a S/N greater than 3 in the 0.29 wide field;
  • the photometry is derived from the GSC catalog. The faintest source has a 17.2 magnitude;
  • intruders are searched by comparing the source coordinates with the USNO-A2.0 catalog:
    • 19 intruders are found, all outside the error box;
    • 2 intruders are detected as "defects", i.e. with a fwhm much smaller than the average (hot pixel or cosmic);
    • the 17 remaining intruders are in the DSS.

Therefore there is no counterpart down to a magnitude of 17.2.

The 3x200s stacked image:

Red circle: the error box for the gamma ray burst. Green diamonds: the 19 intruders, i.e. sources with S/N greater than 3 that are not in the USNO-A2.0 catalog.


No other observer found an optical counterpart.

Technical notes

Telescope and camera configuration.

Computer and software configuration.

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